Sicilian Defence
Encyclopedia
The Sicilian Defence is a chess
Chess
Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...

 opening
Chess opening
A chess opening is the group of initial moves of a chess game. Recognized sequences of opening moves are referred to as openings as initiated by White or defenses, as created in reply by Black. There are many dozens of different openings, and hundreds of named variants. The Oxford Companion to...

 that begins with the moves:
1. e4 c5


The Sicilian is the most popular and best-scoring response to White's first move 1.e4. "Indeed, most statistical surveys suggest that 1.d4 is the most successful first move for White, but only because 1...c5 scores so highly against 1.e4." New in Chess
New In Chess
New In Chess is a chess magazine that appears eight times a year with chief editors International Grandmaster Jan Timman and Dirk Jan Ten Geuzendam. It contains notes by top players and chess prodigies on their own games...

 stated in its 2000 Yearbook that of the games
Game theory
Game theory is a mathematical method for analyzing calculated circumstances, such as in games, where a person’s success is based upon the choices of others...

 in its database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...

, White scored 56.1% in 296,200 games beginning 1.d4, but a full two percentage points lower (54.1%) in 349,855 games beginning 1.e4. "The main culprit responsible for this state of affairs" was the Sicilian, which held White to a 52.3% score in 145,996 games. At the elite level (> 2500 FIDE rating), 1...e5 scores slightly better, mainly because of the difficulty in breaking down defences such as the Berlin Wall.

One sixth (17%) of all games between grandmasters, and one quarter (25%) of the games in the Chess Informant
Chess Informant
Chess Informant is a publishing company from Belgrade that periodically produces a book of the same name, as well as the Encyclopaedia of Chess Openings, Encyclopaedia of Chess Endings, Opening Monographs, other print publications, and software Chess Informant (Šahovski Informator) is a...

 database, begin with the Sicilian. Almost one quarter of all games use the Sicilian Defence.

Grandmaster John Nunn
John Nunn
John Denis Martin Nunn is one of England's strongest chess players and once belonged to the world's top ten. He is also a three times world champion in chess problem solving, a chess writer and publisher, and a mathematician....

 attributes the Sicilian Defence's popularity to "its combative nature; in many lines Black is playing not just for equality, but for the advantage. The drawback is that White often obtains an early initiative, so Black has to take care not to fall victim to a quick attack." Grandmaster Jonathan Rowson
Jonathan Rowson
Jonathan Rowson is Scotland's third chess Grandmaster, after Paul Motwani and Colin McNab, and has played first board at recent Chess Olympiads. He is also a chess author.-Career:...

 recently considered why the Sicilian is the most successful response to 1.e4, even though 1...c5 develops no pieces, and the pawn on c5 controls only d4 and b4. Rowson writes:
To my mind there is quite a straightforward explanation. In order to profit from the initiative granted by the first move, White has to make use of his opportunity to do something before Black has an equal number of opportunities of his own. However, to do this, he has to make 'contact' with the black position. The first point of contact usually comes in the form of a pawn exchange, which leads to the opening of the position. ... So the thought behind 1...c5 is this: 'OK, I'll let you open the position, and develop your pieces aggressively, but at a price – you have to give me one of your centre pawns.'


The earliest recorded notes on the Sicilian Defence date back to the late 16th century by the Italian chess players Giulio Polerio
Giulio Polerio
Giulio Cesare Polerio , was an Italian chess theoretician and player....

 and Gioachino Greco.

General concepts

By advancing the c-pawn
Pawn (chess)
The pawn is the most numerous and weakest piece in the game of chess, historically representing infantry, or more particularly armed peasants or pikemen. Each player begins the game with eight pawns, one on each square of the rank immediately in front of the other pieces...

 two squares, Black asserts control over the d4-square and begins the fight for the centre of the board. The move resembles 1…e5, the next most common response to 1.e4, in that respect. Unlike 1...e5, however, 1...c5 breaks the symmetry of the position, which strongly influences both players' future actions. White, having pushed a kingside pawn, tends to hold the initiative
Initiative (chess)
Initiative in a chess position belongs to the player who can make threats that cannot be ignored. He thus puts his opponent in the position of having to use his turns responding to threats rather than making his own. A player with the initiative will often seek to maneuver his pieces into more and...

 on that side of the board. Moreover, 1...c5 does little for Black's development, unlike moves such as 1...e5, 1...g6, or 1...Nc6, which either develop a minor piece or prepare to do so. In many variations of the Sicilian, Black makes a number of further pawn moves in the opening (for example, ...d6, ...e6, ...a6, and ...b5). Consequently, White often obtains a substantial lead in development and dangerous attacking chances.

Meanwhile, Black's advance of a queenside pawn has given him a spatial advantage there and provides a basis for future operations on that flank. Often, Black's pawn on c5 is traded for White's pawn on d4 in the early stages of the game, granting Black a central pawn majority. The pawn trade also opens the c-file for Black, who can place a rook or queen on that file to aid his queenside counterplay.

History

The Sicilian Defence was analysed by Giulio Polerio
Giulio Polerio
Giulio Cesare Polerio , was an Italian chess theoretician and player....

 in his 1594 manuscript on chess, though he did not use the term "Sicilian Defence". It was later the subject of analyses by leading players of the day Alessandro Salvio (1604), Don Pietro Carrera (c. 1617), and Gioachino Greco (1623), and later Comte Carlo Francesco Cozio (c. 1740). The great French player and theoretician André Danican Philidor
François-André Danican Philidor
François-André Danican Philidor , often referred to as André Danican Philidor during his lifetime, was a French composer and chess player. He contributed to the early development of the opéra comique...

 opined of the Sicilian in 1777, "This way of opening the game ... is absolutely defensive, and very far from being the best ... but it is a very good one to try the strength of an adversary with whose skill you are unacquainted."

In 1813, the English master Jacob Henry Sarratt effectively standardised his English translation of the name of this opening as "the Sicilian Defence", referring to an old Italian manuscript that used the phrase, "il giocho siciliano" ("The Sicilian Game"). The Sicilian was fairly popular for much of the nineteenth century; Louis-Charles Mahé de La Bourdonnais
Louis-Charles Mahé de La Bourdonnais
Louis-Charles Mahé de La Bourdonnais was a French chess master, possibly the strongest player in the early 19th century.- Early life :...

, Adolf Anderssen
Adolf Anderssen
Karl Ernst Adolf Anderssen was a German chess master. He is considered to have been the world's leading chess player in the 1850s and 1860s...

, Howard Staunton
Howard Staunton
Howard Staunton was an English chess master who is generally regarded as having been the world's strongest player from 1843 to 1851, largely as a result of his 1843 victory over Saint-Amant. He promoted a chess set of clearly distinguishable pieces of standardised shape—the Staunton pattern—that...

, Louis Paulsen
Louis Paulsen
Louis Paulsen was a German chess player.In 1860s and 1870s, he was among the top five players in the world. He was a younger brother of Wilfried Paulsen....

, and Carl Jaenisch
Carl Jaenisch
Carl Friedrich Andreyevich von Jaenisch was a Finnish and Russian chess player and theorist. In the 1840s, he was among the top players in the world.-Life and career:...

 all played it with some consistency. In the ninth edition of Modern Chess Openings, Walter Korn
Walter Korn
Walter Korn was an author of books and magazine articles about chess. Despite his status as a writer, there is no known record of him playing tournament chess, and few chess players ever met him...

 noted that the Sicilian "received three of its earliest practical tests, and a big boost in popularity, in the 1834 MacDonnell
Alexander McDonnell
Alexander McDonnell was an Irish chess master, who contested a series of six matches with the world’s leading player Louis-Charles Mahé de La Bourdonnais in the summer of 1834.- Early life :...

 [sic]–La Bourdonnais match, 1843 Staunton–St. Amant match, and the 1851 London Tournament." Staunton wrote of the Sicilian, "In the opinion of Jaenisch and the German 'Handbuch
Handbuch des Schachspiels
Handbuch des Schachspiels is a chess book, first published in 1843 by Tassilo von Heydebrand und der Lasa. It was one of the most important opening references for many decades...

', with which I coincide, this is the best possible reply to 1.P-K4, [1.e4 in algebraic notation] 'as it renders the formation of a centre impracticable for White and prevents every attack.' "

The opening fell out of favour in the later part of the nineteenth century, when some of the world's leading players rejected it. Paul Morphy
Paul Morphy
Paul Charles Morphy was an American chess player. He is considered to have been the greatest chess master of his era and an unofficial World Chess Champion. He was a chess prodigy...

, the world's best player in the late 1850s, decried "that pernicious fondness for the Sicilian Defense ... extending from about 1843 to some time after 1851". Wilhelm Steinitz
Wilhelm Steinitz
Wilhelm Steinitz was an Austrian and then American chess player and the first undisputed world chess champion from 1886 to 1894. From the 1870s onwards, commentators have debated whether Steinitz was effectively the champion earlier...

, the first World Champion
World Chess Championship
The World Chess Championship is played to determine the World Champion in the board game chess. Men and women of any age are eligible to contest this title....

, also disliked the Sicilian and rejected it in favour of 1...e5. The death of the opening's two greatest proponents, Staunton and Anderssen, in 1874 and 1879 respectively, also contributed to its decline. It has been said that "[t]hese losses almost dealt a knock-out blow to the Sicilian because it took a long time to find such important figures to carry the Sicilian's standard." George H. D. Gossip
George H. D. Gossip
George Hatfeild Dingley Gossip was a minor American-English chess master and writer. He competed in chess tournaments between 1870 and 1895, playing against most of the world's leading players, but with only modest success. The writer G. H...

, in The Chess Player's Manual, first published in 1874, wrote, "Of late years ... discoveries have been made which have the effect of considerably strengthening White's attack, and the 'Sicilian' is now considered by most modern authorities to be a comparatively weak mode of play." Freeborough
Edward Freeborough
Edward Freeborough was the co-author, with Charles Ranken, of Chess Openings Ancient and Modern , one of the first important opening treatises in the English language and a precursor of Modern Chess Openings. He was a member of the editorial staff of the British Chess Magazine from 1883 until his...

 and Ranken
Charles Ranken
Charles Edward Ranken was a Church of England clergyman and a minor British chess master. He co-founded and was the first president of the Oxford University Chess Club. He was also the editor of the Chess Player's Chronicle and a writer for the British Chess Magazine...

, in their treatise Chess Openings: Ancient and Modern (1889, 1896), wrote that the Sicilian "had at one time the reputation of being the best reply to 1.P-K4, but this has not been confirmed by popular practice. Several eminent players have, however, held to the opinion that it is quite trustworthy."

The Sicilian continued to be shunned by most leading players at the start of the twentieth century, as 1...e5 held centre stage. Capablanca
José Raúl Capablanca
José Raúl Capablanca y Graupera was a Cuban chess player who was world chess champion from 1921 to 1927. One of the greatest players of all time, he was renowned for his exceptional endgame skill and speed of play...

, World Champion from 1921 to 1927, famously denounced it as an opening where "Black's game is full of holes". Similarly, James Mason
James Mason (chess player)
James Mason was a famous chess player and writer. He was born in Kilkenny in Ireland. His original name is unknown: he was adopted as a child and only took the name James Mason when he and his family moved to the United States in 1861...

 wrote, "Fairly tried and found wanting, the Sicilian has now scarcely any standing as a first-class defence. ... [It] is too defensive. There are too many holes created in the Pawn line. Command of the field, especially in the centre, is too readily given over to the invading force." Siegbert Tarrasch
Siegbert Tarrasch
Siegbert Tarrasch was one of the strongest chess players and most influential chess teachers of the late 19th century and early 20th century....

 wrote that 1...c5 "is certainly not strictly correct, for it does nothing toward development and merely attempts to render difficult the building up of a centre by the first player. ... [T]he Sicilian Defence is excellent for a strong player who is prepared to take risks to force a win against an inferior opponent. Against best play, however, it is bound to fail." The Sicilian was not seen even once in the 75 games played at the great St. Petersburg 1914 tournament
St. Petersburg 1914 chess tournament
The tournament celebrated the tenth anniversary of the St. Petersburg Chess Society. The president of the organizing committee was Peter Petrovich Saburov. Members of the committee were: Boris Maliutin, Peter Alexandrovich Saburov, and O. Sossnitzky...

.

Nonetheless, some leading players, such as Emanuel Lasker
Emanuel Lasker
Emanuel Lasker was a German chess player, mathematician, and philosopher who was World Chess Champion for 27 years...

 (World Champion from 1894 to 1921), Frank Marshall, Savielly Tartakower
Savielly Tartakower
Ksawery Tartakower was a leading Polish and French chess Grandmaster. He was also a leading chess journalist of the 1920s and 30s...

, and Aron Nimzowitsch
Aron Nimzowitsch
Aron Nimzowitsch was a Russian-born Danish unofficial chess grandmaster and a very influential chess writer...

, and later Max Euwe
Max Euwe
Machgielis Euwe was a Dutch chess Grandmaster, mathematician, and author. He was the fifth player to become World Chess Champion . Euwe also served as President of FIDE, the World Chess Federation, from 1970 to 1978.- Early years :Euwe was born in Watergraafsmeer, near Amsterdam...

 (World Champion from 1935 to 1937) played the Sicilian. Even Capablanca and Tarrasch, despite their critical comments, occasionally played the opening. It was played six times (out of 110 games) at New York 1924
New York 1924 chess tournament
New York 1924 was an elite chess tournament held in the Alamac Hotel in New York City from March 6 to April 18, 1924. It was organized by the Manhattan Chess Club. The competitors included world champion José Raúl Capablanca and his predecessor Emanuel Lasker. Nine other top players from Europe...

. The following year, the authors of Modern Chess Openings
Modern Chess Openings
Modern Chess Openings is an important reference book on the chess openings, first published in 1911 by the British players Richard Clewin Griffith and John Herbert White...

(4th edition) wrote, "The Sicilian has claims to be considered as the best of the irregular defences to 1.P-K4 at Black's disposal, and has been practised with satisfactory results by the leading players of the day." In this period Black's approach was usually slow and positional, and the all-out attacks by White that became common after World War II had not yet been developed.

The fortunes of the Sicilian were further revived in the 1940s and 1950s by players such as Isaac Boleslavsky
Isaac Boleslavsky
Isaac Yefremovich Boleslavsky was a Soviet–Jewish chess Grandmaster.-Early career:Boleslavsky taught himself chess at age 9...

, Alexander Kotov
Alexander Kotov
Alexander Alexandrovich Kotov was a Soviet chess grandmaster and author. He was a Soviet champion, a two-time world title Candidate, and a prolific chess author. Kotov served in high posts in the Soviet Chess Federation and most of his books were written during the period of Cold War between the...

, and Miguel Najdorf
Miguel Najdorf
Miguel Najdorf was a Polish-born Argentine chess grandmaster of Jewish origin, famous for his Najdorf Variation....

. Reuben Fine
Reuben Fine
Reuben Fine was one of the strongest chess players in the world from the early 1930s through the 1940s, an International Grandmaster, psychologist, university professor, and author of many books on both chess and psychology.Fine won five medals in three chess Olympiads. Fine won the U.S...

, one of the world's leading players during this time period, wrote of the Sicilian in 1948, "Black gives up control of the centre, neglects his development, and often submits to horribly cramped positions. How can it be good? Yet, the brilliant wins by White are matched by equally brilliant wins by Black; time and again the Black structure has been able to take everything and come back for more."

Later, Bent Larsen
Bent Larsen
Jørgen Bent Larsen was a Danish chess Grandmaster and author. Larsen was known for his imaginative and unorthodox style of play and he was the first western player to pose a serious challenge to the Soviet Union's dominance of chess...

, Ljubomir Ljubojevic
Ljubomir Ljubojevic
Ljubomir Ljubojević is a Grandmaster of chess. He was born on November 2, 1950, in Titovo Užice, Yugoslavia . Ljubojević was awarded the International Master title in 1970 and the GM title in 1971. He was Yugoslav champion in 1977 and 1982. He won the 1974 Canadian Open Chess Championship...

, Lev Polugaevsky
Lev Polugaevsky
Lev Abramovich Polugaevsky was an International Grandmaster of chess and frequent contender for the world chess championship, although he never achieved that title...

, Leonid Stein
Leonid Stein
Leonid Zakharovich Stein was a Soviet chess Grandmaster from Ukraine. He won three USSR Chess Championships in the 1960s , and was among the world's top ten players during that era.- Early life :...

, Mark Taimanov
Mark Taimanov
Mark Evgenievich Taimanov is a leading Soviet and Russian chess player and concert pianist.-Chess:He was awarded the International Grandmaster title in 1952 and played in the Candidates Tournament in Zurich in 1953, where he tied for eighth place. From 1946 to 1956, he was among the world's top...

, and Mikhail Tal
Mikhail Tal
Mikhail Tal was a Soviet–Latvian chess player, a Grandmaster, and the eighth World Chess Champion.Widely regarded as a creative genius, and the best attacking player of all time, he played a daring, combinatorial style. His play was known above all for improvisation and unpredictability....

 all made extensive contributions to the theory and practice of the defence. Through the efforts of world champions Bobby Fischer
Bobby Fischer
Robert James "Bobby" Fischer was an American chess Grandmaster and the 11th World Chess Champion. He is widely considered one of the greatest chess players of all time. Fischer was also a best-selling chess author...

 and Garry Kasparov
Garry Kasparov
Garry Kimovich Kasparov is a Russian chess grandmaster, a former World Chess Champion, writer, political activist, and one of the greatest chess players of all time....

, the Sicilian Defence became recognised as the defence that offered Black the most winning chances against 1.e4. Both players favoured sharp, aggressive play and employed the Sicilian almost exclusively throughout their careers, burnishing the defence's present reputation. Today, most leading grandmasters include the Sicilian in their opening repertoire. Some of the current top-level players who regularly use it include Peter Leko
Péter Lékó
On the way to winning the prestigious Corus chess tournament in 2005, Lékó defeated Grandmaster Viswanathan Anand with the black pieces. The moves were:...

, Viswanathan Anand
Viswanathan Anand
V. Anand or Anand Viswanathan, usually referred as Viswanathan Anand, is an Indian chess Grandmaster, the current World Chess Champion, and currently second highest rated player in the world....

, Boris Gelfand
Boris Gelfand
Boris Abramovich Gelfand is a Belarus-born Israeli chess Grandmaster. He won the 2011 Candidates Tournament and will challenge Viswanathan Anand for the World Chess Championship 2012.-Biography:...

, Vassily Ivanchuk, Alexei Shirov
Alexei Shirov
Alexei Dmitrievich Shirov is a Soviet-born Latvian chess grandmaster. He has consistently ranked among the world's top players since the early 1990s, and reached a ranking as high as number four in 1998...

, Peter Svidler
Peter Svidler
Peter Veniaminovich Svidler is a Russian chess grandmaster.He is six-time Russian champion ....

, and Veselin Topalov
Veselin Topalov
Veselin Aleksandrov Topalov is a Bulgarian chess grandmaster. He currently has the sixth highest rating in the world, and was the challenger facing world champion Viswanathan Anand in the World Chess Championship 2010, losing the match 6½–5½....

. In 1990, the authors of Modern Chess Openings (13th edition) noted that "in the twentieth century the Sicilian has become the most played and most analysed opening at both the club and master levels." In 1965, in the tenth edition of that book, grandmaster Larry Evans
Larry Evans
For the football player of the same name, see Larry Evans .Larry Melvyn Evans was an American chess grandmaster, author, and journalist. He won or shared the U.S. Chess Championship five times and the U.S. Open Chess Championship four times...

 observed that, "The Sicilian is Black's most dynamic, asymmetrical reply to 1.P-K4. It produces the psychological and tension factors which denote the best in modern play and gives notice of a fierce fight on the very first move."

Open Sicilian: 2.Nf3 and 3.d4

Over 75% of games beginning with 1.e4 c5 continue with 2.Nf3, when there are three main options for Black: 2...d6, 2...Nc6, and 2...e6. Lines where White then plays 3.d4 are collectively known as the Open Sicilian, and result in extremely complex positions. White has a lead in development and extra kingside space, which White can use to begin a kingside attack. This is counterbalanced by Black's central pawn majority, created by the trade of White's d-pawn for Black's c-pawn, and the open c-file, which Black uses to generate queenside counterplay.

2...d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3

Black's most common move after 2.Nf3 is 2...d6. This prepares ...Nf6 to attack the e-pawn without letting White push it to e5. The game usually continues 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3. Sometimes played is 3...Nf6 4.Nc3 cxd4 5.Nxd4 giving the same result. Black can then choose between four major variations: in order of decreasing popularity, these are the Najdorf (5...a6), Dragon (5...g6), Classical (5...Nc6), and Scheveningen (5...e6). The Venice Attack (5...e5 6.Bb5+) and Kupreichik Variation (5...Bd7) are rarely played. 5...e5 is often considered something of an error on Black's part and 5...Bd7 can transpose
Transposition (chess)
A transposition in chess is a sequence of moves that results in a position which may also be reached by another, more common sequence of moves. Transpositions are particularly common in opening, where a given position may be reached by different sequences of moves...

 to one of the more common variations, such as the Classical or Dragon, but there are also a number of independent lines.

There are a few ways for either side to deviate from the moves given above. After 3...cxd4, White occasionally plays 4.Qxd4, the Chekhover Variation, intending to meet 4...Nc6 with 5.Bb5 Bd7 6.Bxc6, when White hopes that his lead in development compensates for Black's bishop pair. Black can avoid this line by playing 3...Nf6, when 4.Nc3 cxd4 5.Nxd4 returns to main lines. However, White has the option of 4.dxc5!?, when Black can play either 4...Nxe4 or 4...Qa5+. Another unusual sideline is 3...cxd4 4.Nxd4 Nf6 5.f3!?, the Prins Variation, which tries to maintain the option of c4 with a Maróczy Bind
Maróczy Bind
The Maróczy Bind is a pawn formation in chess, named after the Hungarian grandmaster Géza Maróczy and primarily, but not exclusively, played against the Sicilian Defence. It is characterized by white pawns on c4 and e4, with White's d-pawn having been exchanged for Black's c-pawn...

 formation.

Najdorf Variation: 5...a6

The Najdorf Variation is Black's most popular system in the Sicilian Defence. Najdorf's
Miguel Najdorf
Miguel Najdorf was a Polish-born Argentine chess grandmaster of Jewish origin, famous for his Najdorf Variation....

 intention with 5...a6 was to prepare ...e5 on the next move to gain space in the centre; the immediate 5...e5?! however is met by 6.Bb5+!, when Black must either play 6...Bd7 or 6...Nbd7. The former allows White to exchange off Black's light-squared bishop, after which the d5-square becomes very weak; but the latter allows 7.Nf5, when Black can only save the d-pawn by playing the awkward 7...a6 8.Bxd7+ Qxd7. In both cases, White's game is preferable.

Thus, by playing 5...a6, Black deprives White of the check on b5, so that ...e5 might be possible next move. In general, 5...a6 also prevents White's knights from using the b5-square, and helps Black create queenside play by preparing the ...b5 pawn push. This plan of 5...a6 followed by ...e5 represents Black's traditional approach in the Najdorf Variation. Later, Garry Kasparov
Garry Kasparov
Garry Kimovich Kasparov is a Russian chess grandmaster, a former World Chess Champion, writer, political activist, and one of the greatest chess players of all time....

 also adopted the 5...a6 move order, but with the idea of playing ...e6 rather than ...e5. Kasparov's point is that the immediate 5...e6 (the Scheveningen Variation, discussed below) allows 6.g4, which is White's most dangerous line against the Scheveningen. By playing 5...a6 first, Black temporarily prevents White's g4 thrust and waits to see what White plays instead. Often, play will eventually transpose to the Scheveningen Variation.

Currently, White's most popular weapon against the Najdorf is 6.Be3. This is called the English Attack, because it was popularised by English grandmasters Murray Chandler
Murray Chandler
Murray Graham Chandler is a New Zealand chess grandmaster who has played internationally for that nation and for England, after gaining citizenship there in the early 1980s...

, John Nunn
John Nunn
John Denis Martin Nunn is one of England's strongest chess players and once belonged to the world's top ten. He is also a three times world champion in chess problem solving, a chess writer and publisher, and a mathematician....

 and Nigel Short
Nigel Short
Nigel David Short MBE is an English chess grandmaster earning the title at the age of 19. Short is often regarded as the strongest English player of the 20th century as he was ranked third in the world, from January 1988 – July 1989 and in 1993, he challenged Garry Kasparov for the World Chess...

 in the 1980s. White's idea is to play f3, Qd2, g4 and 0-0-0 in some order. Black can respond with 6...e6, 6...e5 or 6...Ng4; to prevent ...Ng4, White sometimes starts with 6.f3 instead. A related attacking idea for White is 6.Be3 e6 7.g4, known as the Hungarian Attack or Perenyi Attack.

Formerly, 6.Bg5 e6 7.f4 was the main line of the Najdorf, when White threatens to attack the pinned knight with 8.e5. Black can simply break the pin with 7...Be7, when White usually plays 8.Qf3 and 9.0-0-0. Some of Black's alternatives are 7...Qb6, the Poisoned Pawn Variation
Poisoned Pawn Variation
The Poisoned Pawn Variation is any of several chess opening variations where a pawn is said to be "poisoned" because its capture can result in positional problems or material loss for the captor. The best known of these, called the Poisoned Pawn Variation, is a line of the Sicilian Defense, Najdorf...

 popularized by Fischer
Bobby Fischer
Robert James "Bobby" Fischer was an American chess Grandmaster and the 11th World Chess Champion. He is widely considered one of the greatest chess players of all time. Fischer was also a best-selling chess author...

, and 7...b5, the Polugaevsky
Lev Polugaevsky
Lev Abramovich Polugaevsky was an International Grandmaster of chess and frequent contender for the world chess championship, although he never achieved that title...

 Variation, which has the tactical point 8.e5 dxe5 9.fxe5 Qc7! 10.exf6 Qe5+ winning the bishop in return for the knight.

White has other choices on the sixth move. 6.Be2 prepares to castle kingside and is a quieter alternative compared to 6.Be3 and 6.Bg5. Efim Geller
Efim Geller
Efim Petrovich Geller was a Soviet chess player and world-class grandmaster at his peak. He won the Soviet Championship twice and was a Candidate for the World Championship on six occasions...

 was an early proponent of this move, after which Black can stay in "pure" Najdorf territory with 6...e5 or transpose to the Scheveningen with 6...e6. Other possibilities for White include 6.f4, 6.Bc4 (the Fischer Attack), 6.g3, and 6.h3, (the Adams Attack, named after Weaver Adams), which was used several times by Bobby Fischer
Bobby Fischer
Robert James "Bobby" Fischer was an American chess Grandmaster and the 11th World Chess Champion. He is widely considered one of the greatest chess players of all time. Fischer was also a best-selling chess author...

.

Dragon Variation: 5...g6

In the Dragon Variation, Black fianchetto
Fianchetto
In chess the fianchetto is a pattern of development wherein a bishop is developed to the second rank of the adjacent knight file, the knight pawn having been moved one or two squares forward....

es a Bishop on the h8–a1 diagonal. It was named by Fyodor Dus-Chotimirsky in 1901, who noticed a resemblance between Black's kingside pawn structure (pawns on d6, e7, f7, g6 and h7) and the stars of the Draco constellation
Draco (constellation)
Draco is a constellation in the far northern sky. Its name is Latin for dragon. Draco is circumpolar for many observers in the northern hemisphere...

. White's most dangerous try against the Dragon is the Yugoslav Attack, characterised by 6.Be3 Bg7 7.f3 0-0 8.Qd2 Nc6, when both 9.0-0-0 and 9.Bc4 are played. This variation leads to extremely sharp play and is ferociously complicated, since the players castle on opposite wings and the game becomes a race between White's kingside attack and Black's queenside counterattack. White's main alternatives to the Yugoslav Attack are 6.Be2, the Classical Variation, and 6.f4, the Levenfish Attack.

Classical Variation: 5...Nc6

This variation can arise from two different move orders: 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Nc6, or 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 d6. Black simply brings his knight to its most natural square, and defers, for the moment, the development of his king's bishop.

White's most common reply is 6.Bg5, the Richter–Rauzer Attack. The move 6.Bg5 was Kurt Richter
Kurt Richter
Kurt Paul Otto Joseph Richter was a German chess International Master and chess writer.- Chess achievements :...

's invention, threatening to double Black's pawns after Bxf6 and forestalling the Dragon by rendering 6....g6 unplayable. After 6...e6, Vsevolod Rauzer
Vsevolod Rauzer
Vsevolod Rauzer is probably best known for his extensive chess opening theory. The Richter–Rauzer Variation of the Sicilian Defence , was named in honor of him and the German master Kurt Richter....

 introduced the modern plan of Qd2 and 0-0-0 in the 1930s. White's pressure on the d6-pawn often compels Black to respond to Bxf6 with ...gxf6, rather than recapturing with a piece (e.g. the queen on d8) that also has to defend the d-pawn. This weakens his kingside pawn structure
Pawn structure
In chess, the pawn structure is the configuration of pawns on the chessboard. Since pawns are the least mobile of the chess pieces, the pawn structure is relatively static and thus largely determines the strategic nature of the position.-General observations:Weaknesses in the pawn structure, such...

, in return for which Black gains the two bishops, plus a central pawn majority, though these assets are difficult to exploit.

Another popular variation is 6.Bc4, which brings the bishop to an aggressive square. Black usually plays 6...e6 to limit the range of White's bishop, but White can eventually put pressure on the e6-pawn by pushing his f-pawn to f5. After the moves 7.Be3 Be7, White can either castle
Castling
Castling is a special move in the game of chess involving the king and either of the original rooks of the same color. It is the only move in chess in which a player moves two pieces at the same time. Castling consists of moving the king two squares towards a rook on the player's first rank, then...

 kingside (the Fischer–Sozin Attack, named after Bobby Fischer
Bobby Fischer
Robert James "Bobby" Fischer was an American chess Grandmaster and the 11th World Chess Champion. He is widely considered one of the greatest chess players of all time. Fischer was also a best-selling chess author...

 and Russian master Veniamin Sozin, who originated it in the 1930s), or queenside with 8.Qe2 and 9.0-0-0 (the Velimirović
Dragoljub Velimirovic
Dragoljub Velimirović is a Serbian and former Yugoslav chess grandmaster, born in Valjevo.-Biography:...

 Attack). Instead of 6...e6, Black can also try Benko's
Pál Benko
Pal Benko is a chess grandmaster, author, and composer of endgame studies and chess problems.- Early life :Benko was born in France but was raised in Hungary. He was Hungarian champion by age 20. He emigrated to the United States in 1958, after defecting following the World Student Team...

 move 6...Qb6, which forces White to take a decision over the knight at d4, and typically leads the game into more positional lines than the razor-sharp, highly theoretical Sozin and Velimirovic variations. 6.Be2 allows Black to choose among 6...e5, the dynamic Boleslavsky
Isaac Boleslavsky
Isaac Yefremovich Boleslavsky was a Soviet–Jewish chess Grandmaster.-Early career:Boleslavsky taught himself chess at age 9...

 Variation; 6...e6, transposing to the Scheveningen Variation; and 6...g6, transposing to the Classical Variation of the Dragon.

Scheveningen Variation: 5...e6

In the Scheveningen Variation, Black contents himself with a "small centre" (pawns on d6 and e6, rather than e5) and prepares to castle kingside. In view of this, Paul Keres
Paul Keres
Paul Keres , was an Estonian chess grandmaster, and a renowned chess writer. He was among the world's top players from the mid-1930s to the mid-1960s....

 introduced 6.g4, the Keres Attack, in 1943. White intends to drive away the black knight with g5. If Black prevents this with 6...h6, which is the most common answer, White has gained kingside space and discouraged Black from castling in that area, and may later play Bg2. If the complications after 6.g4 are not to White's taste, a major alternative is 6.Be2, a typical line being 6...a6 (this position can be reached from the Najdorf via 5...a6 6.Be2 e6) 7.0-0 Be7 8.f4 0-0. 6.Be3 and 6.f4 are also common.

While theory indicates that Black can hold the balance in the Keres Attack, players today often prefer to avoid it by playing 5...a6 first, an idea popularized by Kasparov. However, if White is determined to play the g4 thrust, he may prepare it by responding to 5...a6 with 6.h3 (as Fischer sometimes played) or 6.Rg1.

2...Nc6 3.d4 cxd4 4.Nxd4

2...Nc6 is a natural developing move, and also prepares ...Nf6 (like 2...d6, Black stops White from replying e5). After 3.d4 cxd4 4.Nxd4, Black's most common move is 4...Nf6, when White usually replies 5.Nc3. At this point, Black can play 5...d6, transposing to the Classical Variation; 5...e5, the Sveshnikov Variation; or 5...e6, transposing to the Four Knights Variation. Apart from 4...Nf6, Black's most important moves are 4...e6 (transposing to the Taimanov Variation), 4...g6 (the Accelerated Dragon) and 4...e5 (the Kalashnikov Variation). Rarer choices include 4...Qc7, which may later transpose to the Taimanov Variation, and 4...Qb6, the Grivas
Efstratios Grivas
Efstratios Grivas is a Greek chess Grandmaster.-Early years:He was born in Egio, Achaia and grew up in Athens, in the neighbourhood of Kallithea, as his family moved to the Greek capital in 1970. His registration at the Kallithea Chess Club in 1979 was his first contact with chess...

 Variation.

Sveshnikov Variation: 4...Nf6 5.Nc3 e5

The Sveshnikov Variation was pioneered by Evgeny Sveshnikov
Evgeny Sveshnikov
Evgeny Ellinovich Sveshnikov is a Latvian, former Soviet International Grandmaster of chess, and a chess writer.-The player:...

 and Gennadi Timoshchenko in the 1970s. Before their efforts, the variation was called the Lasker–Pelikan Variation. Emanuel Lasker
Emanuel Lasker
Emanuel Lasker was a German chess player, mathematician, and philosopher who was World Chess Champion for 27 years...

 played it once in his world championship match against Carl Schlechter
Carl Schlechter
Carl Schlechter was a leading Austrian chess master and theoretician at the turn of the 20th century. He is best known for drawing a World Chess Championship match with Emanuel Lasker.-Early life:...

, and Jorge Pelikan played it a few times in the 1950s, but Sveshnikov's treatment of the variation was the key to its revitalization. The move 5...e5 seems anti-positional as it leaves black with a backwards d-pawn and a weakness on d5. Also, black would have to accept the doubled f-pawns in the main line of the opening. The opening was popularised when Sveshnikov saw its dynamic potential for black in the 1970s and 80s. Today, it is extremely popular among grandmasters and amateurs alike. Though some lines still give black trouble, it has been established as a first-rate defense. The main line after 5...e5 runs as follows:

6.Ndb5

The theoretically critical move, threatening Nd6+. All other moves are considered to allow Black easy equality. 6.Nxc6 is usually met by 6...bxc6, when Black's extra pawn in the centre gives him good play; alternatively, even 6...dxc6 7.Qxd8+ Kxd8 is sufficient for equality. 6.Nb3 and 6.Nf3 can be well met by 6...Bb4, threatening to win White's pawn on e4. 6.Nf5 allows 6...d5! 7.exd5 Bxf5 8.dxc6 bxc6 9.Qf3 Qd7. 6.Nde2 can be met by either 6...Bc5 or 6...Bb4.

6...d6

Black does not allow 7.Nd6+ Bxd6 8.Qxd6, when White's pair of bishops give him the advantage.

7.Bg5

White gets ready to eliminate the knight on f6, further weakening Black's control over the d5-square. A less common alternative is 7.Nd5 Nxd5 8.exd5 Nb8 (or 8...Ne7), when White will try to exploit his queenside pawn majority, while Black will seek counterplay on the kingside.

7...a6

Black forces White's knight back to a3.

8.Na3

The immediate 8.Bxf6 forces 8...gxf6, when after 9.Na3, Black can transpose into the main line with 9...b5 or deviate with 9...f5!?

8...b5!

8...b5 was Sveshnikov's innovation, controlling c4 and threatening ...b4 forking White's knights. Previously, Black played 8...Be6 (the Bird Variation), which allowed the a3-knight to return to life with 9.Nc4. The entire variation up to 8...b5 is referred to as the Chelyabinsk
Chelyabinsk
Chelyabinsk is a city and the administrative center of Chelyabinsk Oblast, Russia, located in the northwestern side of the oblast, south of Yekaterinburg, just to the east of the Ural Mountains, on the Miass River. Population: -History:...

 Variation. It can also be reached from the alternate move order 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Nc6 6.Ndb5 d6 7.Bf4 e5 8.Bg5 a6 9.Na3 b5, which is one move longer. (That alternative move order gives White other alternatives, including 6.Nxc6 bxc6 7.e5 Nd5 8.Ne4, intending c4, and the gambit 6.Be2 Bb4 7.0-0!?, allowing Bxc3 8.bxc3 Nxe4.) The move numbers in the following discussion are based on the move order given in bold.
The Sveshnikov Variation has become very popular in master level chess. Black's ...e5 push seems anti-positional: it has made the d6-pawn backward and the d5-square weak. However, in return, Black gets a foothold in the centre and gains time on White's knight, which has been driven to the edge of the board on a3. Top players who have used this variation include Vladimir Kramnik
Vladimir Kramnik
Vladimir Borisovich Kramnik is a Russian chess grandmaster. He was the Classical World Chess Champion from 2000 to 2006, and the undisputed World Chess Champion from 2006 to 2007...

, Veselin Topalov
Veselin Topalov
Veselin Aleksandrov Topalov is a Bulgarian chess grandmaster. He currently has the sixth highest rating in the world, and was the challenger facing world champion Viswanathan Anand in the World Chess Championship 2010, losing the match 6½–5½....

, Teimour Radjabov
Teimour Radjabov
Radjabov's knight sacrifice, 21. ... Ngxe5, was praised by several strong players for its bravery, including English grandmaster Nigel Short. Said Short of the move, "Radjabov plays very imaginatively... he just won't give up, he is extremely tenacious and will always find a way to muddy the...

, Boris Gelfand
Boris Gelfand
Boris Abramovich Gelfand is a Belarus-born Israeli chess Grandmaster. He won the 2011 Candidates Tournament and will challenge Viswanathan Anand for the World Chess Championship 2012.-Biography:...

, Michael Adams and Alexander Khalifman
Alexander Khalifman
Alexander Valeryevich Khalifman is a Soviet and Russian chess Grandmaster of Jewish descent; he is also a former FIDE champion.When Khalifman was 6 years old, he was taught chess by his father....

, among many others.

In the diagrammed position after 8...b5, White usually parries the threat of ...b4 by playing 9.Bxf6 or 9.Nd5. After 9.Bxf6, 9...Qxf6?! 10.Nd5 Qd8 fails to 11.c4 b4 (11...bxc4 12.Nxc4 is good for White, who threatens 13.Qa4) 12.Qa4 Bd7 13.Nb5! axb5 14.Qxa8 Qxa8 15.Nc7+ Kd8 16.Nxa8 and the knight escapes via b6. Thus 9...gxf6 is forced, when White continues 10.Nd5. White's powerful knight on d5 and Black's shattered kingside pawn structure are compensated by Black's bishop pair and White's offside knight on a3. Also, Black has the plan of playing 10...f5, followed by ...fxe4 and ...f5 with the second f-pawn, which would give him good control of the centre. An alternative plan is to play 10...Bg7 followed by ...Ne7 to immediately trade off White's powerful knight; this line is known as the Novosibirsk
Novosibirsk
Novosibirsk is the third-largest city in Russia, after Moscow and Saint Petersburg, and the largest city of Siberia, with a population of 1,473,737 . It is the administrative center of Novosibirsk Oblast as well as of the Siberian Federal District...

 Variation.

Instead of 9.Bxf6, White can also play 9.Nd5, which usually leads to quieter play. White decides not to double Black's f-pawns, and the game usually continues 9...Be7 10.Bxf6 Bxf6 11.c3, when White has maintained his knight on d5 by trading off Black's knight on f6, and prepares to bring the knight on a3 back into play with the manoeuvre Na3–c2–e3. Another line is 10.Nxe7 Nxe7! (fighting for control of d5, and not fearing the doubled pawns) 11.Bxf6 gxf6. A quick draw is possible after 9.Nd5 Qa5+!? 10.Bd2 (in order to prevent 10...Nxe4) 10...Qd8 11.Bg5 Qa5+ etc. In order to avoid this, white can play 11.Nxf6+ or 11.c4.

Accelerated Dragon: 4...g6

Like the standard Dragon Variation, Black develops his bishop to g7 in the Accelerated Dragon. The difference is that Black avoids playing ...d7–d6, so that he can later play ...d7–d5 in one move if possible. For example, if White tries to play in the style of the Yugoslav Attack with 5.Nc3 Bg7 6.Be3 Nf6 7.f3 0-0 8.Qd2, 8...d5! equalises immediately. When White does play 5.Nc3, it is usually with the idea of continuing 5...Bg7 6.Be3 Nf6 7.Bc4 0-0 8.Bb3 (forestalling any tricks involving ...Nxe4 and ...d5), followed by kingside castling.

The critical test of Black's move order is 5.c4, the Maróczy Bind
Maróczy Bind
The Maróczy Bind is a pawn formation in chess, named after the Hungarian grandmaster Géza Maróczy and primarily, but not exclusively, played against the Sicilian Defence. It is characterized by white pawns on c4 and e4, with White's d-pawn having been exchanged for Black's c-pawn...

. White hopes to cramp Black's position by impeding the ...d7–d5 and ...b7–b5 pawn thrusts. Generally, this line is less tactical than many of the other Sicilian variations, and play involves much strategic manoeuvring on both sides. After 5.c4, the main line runs 5...Bg7 6.Be3 Nf6 7.Nc3 and now 7...0-0 or 7...Ng4 is most frequently played.

Kalashnikov Variation: 4...e5 5. Nb5 d6

The Kalashnikov Variation (ECO code B32) is a close relative of the Sveshnikov Variation, and is sometimes known as the Neo-Sveshnikov. The move 4...e5 has had a long history; Louis-Charles Mahé de La Bourdonnais
Louis-Charles Mahé de La Bourdonnais
Louis-Charles Mahé de La Bourdonnais was a French chess master, possibly the strongest player in the early 19th century.- Early life :...

 used it in his matches against Alexander McDonnell
Alexander McDonnell
Alexander McDonnell was an Irish chess master, who contested a series of six matches with the world’s leading player Louis-Charles Mahé de La Bourdonnais in the summer of 1834.- Early life :...

 in 1834, and it was also popular for a short time in the 1940s. These earlier games focused on the Lowenthal Variation with 4...e5 5.Nb5 a6 6.Nd6+ Bxd6 7.Qxd6 Qf6, where Black gives up the two bishops to achieve a lead in development. However, the move fell out of use once it was determined that White kept the advantage in these lines. The Lowenthal Variation is similar to the Kalashnikov but the reply to 5.Nb5 is 5...a6.

Only in the late 1980s did Black players revive 4...e5 with the intention of meeting 5.Nb5 with 5...d6: this is the Kalashnikov Variation. The ideas in this line are similar to those in the Sveshnikov – Black accepts a backward pawn on d6 and weakens the d5-square but gains time by chasing the knight. The difference between the two variations is that Black has not developed his knight to f6 and White has not brought his knight out to c3, so both players have extra options. Black may forego ...Nf6 in favour of ...Ne7, e.g. after 6.N1c3 a6 7.Na3 b5 8.Nd5 Nge7, which avoids White's plan of Bg5 and Bxf6 to inflict doubled f-pawns on Black. Or, Black can delay bringing out the knight in favour of playing ...Be7–g5 or a quick ...f5. On the other hand, White has the option of 6.c4, which solidifies his grip on d5 and clamps down on ...b5, but leaves the d4-square slightly weak.

2...e6 3.d4 cxd4 4.Nxd4

Black's move 2...e6 gives priority to developing the dark-squared bishop. After 3.d4 cxd4 4.Nxd4, Black has three main moves: 4...Nc6 (the Taimanov Variation), 4...a6 (the Kan Variation) and 4...Nf6. After 4...Nf6 5.Nc3, Black can transpose to the Scheveningen Variation with 5...d6, or play 5...Nc6, the Four Knights Variation. Also note that after 4...Nf6 White cannot play 5.e5? because of 5...Qa5+ followed by Qxe5.

Taimanov Variation: 4...Nc6

Named after Mark Taimanov
Mark Taimanov
Mark Evgenievich Taimanov is a leading Soviet and Russian chess player and concert pianist.-Chess:He was awarded the International Grandmaster title in 1952 and played in the Candidates Tournament in Zurich in 1953, where he tied for eighth place. From 1946 to 1956, he was among the world's top...

, the Taimanov Variation can be reached through 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Nc6 or 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e6. Black develops the knight to a natural square and keeps his options open regarding the placement of his other pieces. One of the ideas of this system is to develop the king's bishop to b4 or c5. White can prevent this by 5.Nb5 d6, when 6.c4 leads to a version of the Maróczy Bind
Maróczy Bind
The Maróczy Bind is a pawn formation in chess, named after the Hungarian grandmaster Géza Maróczy and primarily, but not exclusively, played against the Sicilian Defence. It is characterized by white pawns on c4 and e4, with White's d-pawn having been exchanged for Black's c-pawn...

 favoured by Karpov. The resulting position after 6.c4 Nf6 7.N1c3 a6 8.Na3 b6 is a type of Hedgehog.

The Kasparov
Garry Kasparov
Garry Kimovich Kasparov is a Russian chess grandmaster, a former World Chess Champion, writer, political activist, and one of the greatest chess players of all time....

 Gambit 8...d5 was played twice in the World Chess Championship 1985
World Chess Championship 1985
The 1985 World Chess Championship was played between Anatoly Karpov and Garry Kasparov in Moscow from September 3 to November 9, 1985. Kasparov won, to become the thirteenth and youngest world champion at the age of 22.-Background:...

, but virtually disappeared from master praxis after the game Karpov–van der Wiel, Brussels (SWIFT) 1986.

5.Nc3 is more common nowadays than 5.Nb5, when 5...d6 normally transposes to the Scheveningen Variation and 5...Nf6 is the Four Knights Variation (see below). Independent moves for Black are 5...Qc7 and 5...a6, with the former being the more usual move order seen in recent years, as after 5....a6, 6.Nxc6 bxc6 7.Bd3, despite its apparent simplicity, has given Black difficulties in reaching equality. Taimanov's idea was to play 5...a6 (preventing Nb5) followed by ...Nge7 and ...Nxd4.

Kan (Paulsen) Variation: 4...a6

Named after Ilya Kan
Ilya Kan
Ilya Abramovich Kan , was a Russian / Soviet International Master of Chess.He played ten times in Soviet Championships. In 1929, he took 3rd in Odessa . In 1931, he took 7th in Moscow . In 1933, he took 9th in Leningrad...

. By playing 4...a6, Black prevents Nb5 and prepares an eventual ...b5 advance.

White's most popular reply is 5.Nc3 when Black's development of the kingside knight often takes focus as playing Nf6 can be met with e5 which both creates a Black weakness on the d6 square and causes the Black knight a disadvantageous move. So Black normally plays a move to control the e5 square preventing the advancing pawn. The main Kan move is 5...Qc7 although 5...Nc6 transposing into a Taimanov or 5....d6 transposing into a Scheveningen can occur. An alternative idea is to play the immediate 5...b5 and create pressure from the queenside with the idea of playing b4 attacking the c3 knight or Bb7 building pressure along the long white squared diagonal.

An alternative fifth move for white is to play 5.Bd3 when after 5...Bc5 6.Nb3 and now Black can either retreat to Be7 where 7.Qg4 makes Black's kingside problematic or 6...Ba7, 5.c4 is also possible, with a Maróczy bind
Maróczy Bind
The Maróczy Bind is a pawn formation in chess, named after the Hungarian grandmaster Géza Maróczy and primarily, but not exclusively, played against the Sicilian Defence. It is characterized by white pawns on c4 and e4, with White's d-pawn having been exchanged for Black's c-pawn...

 setup.

Four Knights Variation: 4...Nf6 5.Nc3 Nc6

The Four Knights Variation is mainly used as a way of getting into the main line Sveshnikov Variation, reached after 6.Ndb5 d6 7.Bf4 e5 8.Bg5 a6 9.Na3 b5. The point of this move order is to avoid lines such as the Rossolimo
Nicolas Rossolimo
Nicolas Rossolimo was an American-French-Russian-Greek chess Grandmaster. He was many times champion of Paris, France, and after relocating to the United States won the 1955 U.S. Open Championship...

 Variation (1.e4 c5 2.Nf3 Nc6 3.Bb5), or 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 e5 6.Nd5 d6 7.Nd5, which are possible in the standard Sveshnikov move order. On the other hand, in the Four Knights move order, White acquires the extra option of 6.Nxc6 bxc6 7.e5 Nd5 8.Ne4, so White is not obliged to enter the Sveshnikov.

If Black is not aiming for the Sveshnikov, the main alternative is to play 6...Bb4 in reply to 6.Ndb5. Then 7.a3 Bxc3+ 8.Nxc3 d5 9.exd5 exd5 leads to a position where Black has given up the two bishops but has active pieces and the possibility of playing ...d5–d4.

2.Nf3 without 3.d4: White's third move alternatives

White can play 2.Nf3 without intending to follow up with 3.d4. The systems given below are usually classified along with White's second move alternatives as Anti-Sicilians.

2...d6 without 3.d4

After 1.e4 c5 2.Nf3 d6, White's most important alternative to 3.d4 is 3.Bb5+, known as the Moscow Variation or the Canal
Esteban Canal
Esteban Canal was a leading Peruvian chess player who had his best tournament results in the 1920s and 1930s.-Birth and life:Born in Chiclayo, Peru, he moved to Italy in the 1920s and remained there.-As a chess player:...

Sokolsky
Alexey Sokolsky
Alexey Pavlovich Sokolsky was a Ukrainian-Belarusian chess player of International Master strength in over-the board chess, a noted correspondence chess player, and an opening theoretician....

 Attack. Grandmasters sometimes choose this variation when they wish to avoid theory; for instance, it was played by Garry Kasparov
Garry Kasparov
Garry Kimovich Kasparov is a Russian chess grandmaster, a former World Chess Champion, writer, political activist, and one of the greatest chess players of all time....

 in the online game Kasparov–The World
Kasparov versus The World
Kasparov versus the World was a game of chess played in 1999 over the Internet. Conducting the white pieces, Garry Kasparov faced the rest of the world in consultation, with the World Team moves to be decided by plurality vote. Over 50,000 individuals from more than 75 countries participated in the...

. Experts in this line include GMs
International Grandmaster
The title Grandmaster is awarded to strong chess players by the world chess organization FIDE. Apart from World Champion, Grandmaster is the highest title a chess player can attain....

 Sergei Rublevsky
Sergei Rublevsky
Sergei Rublevsky is a Russian chess grandmaster . He won the prestigious Aeroflot Open in 2004, and became the 58th Russian chess champion after winning the Russian Superfinal in Moscow , one point clear from Dmitry Jakovenko and Alexander Morozevich.He finished in the top 10 in the 2005 FIDE...

 and Tomas Oral. Black can block the check with 3...Bd7, 3...Nc6 or 3...Nd7. The position after 3...Nc6 can also be reached via the Rossolimo Variation after 1.e4 c5 2.Nf3 Nc6 3.Bb5 d6.
Most common is 3...Bd7, when after 4.Bxd7+ Qxd7, White can either play 5.0-0 followed by c3 and d4, or 5.c4 in the style of the Maróczy Bind
Maróczy Bind
The Maróczy Bind is a pawn formation in chess, named after the Hungarian grandmaster Géza Maróczy and primarily, but not exclusively, played against the Sicilian Defence. It is characterized by white pawns on c4 and e4, with White's d-pawn having been exchanged for Black's c-pawn...

.

The World Team Variation of the Canal–Sokolsky Attack continues with 5.c4 Nc6 6.Nc3 Nf6 7.0-0 g6 8.d4 cxd4 9.Nxd4 Bg7 10.Nde2 Qe6, forking White's pawns on e4 and c4. This move was suggested by Irina Krush
Irina Krush
Irina Krush is an American chess player who won the U.S. Women's Chess Championship in 1998, 2007, and 2010. Born in Odessa, USSR , she is widely known for her series of chess training videos, the "Krushing Attacks" series.Krush learned to play chess at age five, emigrating with her parents to...

, and played in the Kasparov-The World, 1999
Kasparov versus The World
Kasparov versus the World was a game of chess played in 1999 over the Internet. Conducting the white pieces, Garry Kasparov faced the rest of the world in consultation, with the World Team moves to be decided by plurality vote. Over 50,000 individuals from more than 75 countries participated in the...

 online game. Kasparov noted its novelty.

Another possibility for White is 3.c3, intending to establish a pawn centre with d4 next move. The most frequent continuation is 3...Nf6 4.Be2, when 4...Nxe4?? loses to 5.Qa4+. White sometimes plays 3.Nc3, which usually transposes to the Open Sicilian after 3...Nf6 4.d4.

Recently, 3.Bc4 has been played with decent results, but the theory remains largely unexplored.

2...Nc6 without 3.d4

The Rossolimo Variation, 3.Bb5, is a well-respected alternative to 3.d4. It is named after Nicolas Rossolimo
Nicolas Rossolimo
Nicolas Rossolimo was an American-French-Russian-Greek chess Grandmaster. He was many times champion of Paris, France, and after relocating to the United States won the 1955 U.S. Open Championship...

 and is related to the Moscow Variation. White's usual intention is to play Bxc6, giving Black doubled pawns
Doubled pawns
In chess, doubled pawns are two pawns of the same color residing on the same file. Pawns can become doubled only when one pawn captures onto a file on which another friendly pawn resides. In the diagram, the pawns on the b-file and e-file are doubled...

. Black's major responses are 3...g6 preparing ...Bg7, 3...d6 preparing ...Bd7 (a hybrid line that also arises from the Moscow Variation after 2...d6 3.Bb5+ Nc6), and 3...e6 preparing 4...Nge7. Sergei Rublevsky
Sergei Rublevsky
Sergei Rublevsky is a Russian chess grandmaster . He won the prestigious Aeroflot Open in 2004, and became the 58th Russian chess champion after winning the Russian Superfinal in Moscow , one point clear from Dmitry Jakovenko and Alexander Morozevich.He finished in the top 10 in the 2005 FIDE...

 and Tomas Oral both play this line as well as the Moscow Variation.

3.Nc3 is a common transpositional device for White, who can play 4.d4 or 4.Bb5 next move depending on Black's response. Black sometimes plays 3...e5 to avoid both moves; then 4.Bc4 is considered White's best move. 3.c3 transposes to lines of the Alapin Variation after 3...Nf6 or 3...d5.

2...e6 without 3.d4

White sometimes plays 3.Nc3 as a waiting move, though it has little independent significance. With 3.d3, White plans to develop in King's Indian Attack
King's Indian Attack
The King's Indian Attack , also known as the Barcza System , is a chess opening system for White, most notably used by Bobby Fischer. Its typical formation is shown in the diagram to the right....

 style with g3 and Bg2; this line was used by Fischer to crush Oscar Panno
Oscar Panno
Oscar R. Panno is an Argentine chess Grandmaster.Panno won the World Junior Chess Championship in 1953, and also won the championship of Argentina the same year....

 in a famous game (Fischer–Panno, Buenos Aires
Buenos Aires
Buenos Aires is the capital and largest city of Argentina, and the second-largest metropolitan area in South America, after São Paulo. It is located on the western shore of the estuary of the Río de la Plata, on the southeastern coast of the South American continent...

 1970). 3.c3 will transpose to lines of the Alapin Variation after 3...Nf6, or the French Defence
French Defence
The French Defence is a chess opening. It is characterised by the moves:The French has a reputation for solidity and resilience, though it can result in a somewhat cramped game for Black in the early stages...

 after 3...d5 4.e5 Nc6 5.d4, though 4....d4 is stronger, as after 5.cxd4 cxd4 6.Qa4+ Nc6 7.Bb5 Bd7 8.Bxc6 Bxc6 9.Qxd4 Bxf3 is a strong pawn sacrifice, giving Black excellent compensation. 3.b3, intending Bb2, is a rare independent try, occasinally essayed by Heikki Westerinen
Heikki Westerinen
Heikki Markku Julius Westerinen is a Finnish chess player, born in Helsinki.He became a national master at age sixteen, and earned the FIDE titles of International Master in 1967 and Grandmaster in 1975....

 in the 1970s.

2.Nf3: Black's second move alternatives

After 1.e4 c5 2.Nf3, Black has some rarely played options apart from 2...d6, 2...Nc6 and 2...e6. These include:
  • 2...g6 is the Hyper-Accelerated Dragon or Hungarian Variation, which can transpose to the Dragon or the Accelerated Dragon. Ways for White to prevent this include 3.c3, 3.c4, and 3.d4 cxd4 4.Qxd4, although Black can also meet 3.d4 with 3...Bg7 4. dxc5 Qa5+.
  • 2...a6 is the O'Kelly
    Albéric O'Kelly de Galway
    Albéric O'Kelly de Galway was a Belgian chess Grandmaster , and an International Correspondence Chess Grandmaster , most famous for being the third ICCF World Champion in correspondence chess between 1959 and 1962. He was also a chess writer...

     Variation. The idea is that 3.d4 runs into 3...cxd4 4.Nxd4 Nf6 5.Nc3 e5, when Nb5 is prevented, and Black will equalize by playing ...Bb4 and ...d5 at some point. However, after 3.c3 or 3.c4 it is unclear how 2...a6 has improved Black's position.
  • 2...Nf6 is the Nimzowitsch
    Aron Nimzowitsch
    Aron Nimzowitsch was a Russian-born Danish unofficial chess grandmaster and a very influential chess writer...

     Variation. It bears some similarity to Alekhine's Defence
    Alekhine's Defence
    Alekhine's Defence is a hypermodern chess opening that begins with the moves:Black tempts White's pawns forward to form a broad pawn centre, with plans to undermine and attack the White structure later in the spirit of hypermodern defence. White's imposing mass of pawns in the centre often includes...

    . White's strongest reply is to chase the knight by 3.e5 Nd5 4.Nc3 and now (a) 4...Nxc3 5.dxc3, when 5...b6?, as Nimzowitsch played and recommended, loses to 6.e6! f6 7.Ne5! or (b) 4...e6 (the main line) 5.Nxd5 exd5 6.d4 Nc6 7.dxc5 Bxc5 8.Qxd5 Qb6 (8...d6 9.exd6 Qb6 is also played) 9.Bc4! Bxf2+ 10.Ke2 0-0 11.Rf1 Bc5 12.Ng5 Nd4+ 13.Kd1 with sharp play favoring White.
  • 2...Qc7 is the Quinteros
    Miguel Quinteros
    Miguel Quinteros is an Argentine chess grandmaster.He won the Argentine Chess Championship at the age of 18 and in 1969 took eighth place at the Mar del Plata Zonal tournament...

     Variation. It will frequently transpose into a standard line such as the Taimanov Variation or Paulsen Variation, or else White can play 3.c3 in the style of the Alapin Variation, where Black's queen may not be so well placed on c7.
  • 2... f5 is known as the Brussels Gambit, named after Brussels, Belgium. This used to be thought highly dubious, but has been somewhat rehabilitated by 3.exf5 Nh6, known as the Double-Dutch.

White's second move alternatives

To avoid giving Black the wide choice of systems available after 2.Nf3, White can adopt a number of so-called "anti-Sicilian" lines, including:
  • 2.Nc3 may lead to a variety of systems, depending on White's next move, and has been used by even strong players, who intend to play an open Sicilian, for psychological reasons; while 2....Nc6 or 2....e6 are the usual replies, each obviates the possibility of playing the Najdorf. Lines with 3.g3 are known as the Closed Sicilian; 3.Nf3 usually transposes to the Open Sicilian; and 3.f4 transposes to the Grand Prix Attack (see 2.f4 below). White can also keep his options open with 3. Nge2. Andrew Soltis
    Andrew Soltis
    Andrew Eden Soltis is a chess Grandmaster, author and columnist.He won at Reggio Emilia 1971–72 and was equal first at New York 1977. He was awarded the International Master title in 1974 and became a Grandmaster in 1980...

     has dubbed that the "Chameleon
    Chameleon
    Chameleons are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, the possession by many of a...

     System", since White maintains the option of playing a Closed Sicilian with 4.g3 or transposing to a standard Open Sicilian with 4.d4 cxd4 5.Nxd4. Two drawbacks are that (a) the Closed Sicilian lines with an early Nge2 are not very challenging for Black, and (b) if Black plays 2...Nc6 3.Nge2 g6, 4.d4 reaches an Accelerated Dragon where White has lost the option of playing c4, the Maróczy Bind, often considered White's best line. In view of possible transpositions to the main Sicilian variations, Black's reply to 2.Nc3 will depend on what he plays in the Open Sicilian. 2...Nc6 is the most common choice, but 2...e6 and 2...d6 are often played. The main line of the Closed Sicilian is 2.Nc3 Nc6 3.g3 g6 4.Bg2 Bg7 5.d3 d6, when White's main options are 6.Be3 followed by Qd2 and possibly 0-0-0, and 6.f4 followed by Nf3 and 0-0.
  • 2. c3 is the Alapin Variation or c3 Sicilian. Originally championed by Semyon Alapin
    Semyon Alapin
    Semyon Zinovyevich Alapin was a Russian and Lithuanian chess master, openings analyst, and puzzle composer. He was a linguist, railway engineer and merchant .-Biography:...

     at the end of the 19th century, it was revived in the late 1960s by Evgeny Sveshnikov
    Evgeny Sveshnikov
    Evgeny Ellinovich Sveshnikov is a Latvian, former Soviet International Grandmaster of chess, and a chess writer.-The player:...

     and Evgeny Vasiukov. Nowadays its strongest practitioners include grandmasters Sergei Tiviakov
    Sergei Tiviakov
    Sergei Tiviakov is a naturalised Dutch chess Grandmaster.Tiviakov won the Dutch Chess Championship in 2006 and 2007. In 2008, in Plovdiv, he won the European Individual Chess Championship with 8.5/11....

     and Eduardas Rozentalis
    Eduardas Rozentalis
    Eduardas Rozentalis is a Lithuanian chess grandmaster.He played for the Lithuanian team at first board in seven Chess Olympiads in 1992–98, and 2002–06....

    . White aims to set up a classical pawn centre with 3.d4, so Black should counter immediately in the centre by 2...Nf6 or 2...d5. The line 2...Nf6 3.e5 Nd5 resembles Alekhine's Defence
    Alekhine's Defence
    Alekhine's Defence is a hypermodern chess opening that begins with the moves:Black tempts White's pawns forward to form a broad pawn centre, with plans to undermine and attack the White structure later in the spirit of hypermodern defence. White's imposing mass of pawns in the centre often includes...

    , but the inclusion of the moves c3 and ...c5 is definitely in Black's favour. Now White can play 4.d4 cxd4 5.Nf3, when Black has a choice between 5...e6 and 5...Nc6. Another idea for White is 5.Bc4, which is met by 5....Qc7. 2...d5 3.exd5 Qxd5 4.d4 Nf6 5.Nf3 is the other main line, when Black's main options are 5...e6 and 5...Bg4. In this line, White usually ends up with an isolated
    Isolated pawn
    In chess, an isolated pawn is a pawn which has no friendly pawn on an adjacent file. An isolated queen's pawn is often called an isolani. Isolated pawns are usually a weakness because they cannot be protected by other pawns...

     queen's pawn after pawns are exchanged on d4. A rarer option on Black's second move is 2...e6, with the aim of transposing to the Advance Variation of the French Defence
    French Defence
    The French Defence is a chess opening. It is characterised by the moves:The French has a reputation for solidity and resilience, though it can result in a somewhat cramped game for Black in the early stages...

     after 3.d4 d5 4.e5.


  • 2. f4 is the Grand Prix Attack or McDonnell Attack: the latter name stems from the 14th match game played in London in 1834 between Alexander McDonnell
    Alexander McDonnell
    Alexander McDonnell was an Irish chess master, who contested a series of six matches with the world’s leading player Louis-Charles Mahé de La Bourdonnais in the summer of 1834.- Early life :...

     and Charles Louis Mahé de La Bourdonnais, won by Black. According to Jeremy Silman
    Jeremy Silman
    Jeremy Silman is an American International Master of chess. He has won the US Open, the American Open, and the National Open, and was the coach of the US junior national chess team...

     and others, Black's best reply is 2...d5 3.exd5 Nf6!, the Tal Gambit, which has caused the immediate 2.f4 to decline in popularity. Players usually enter the Grand Prix Attack nowadays by playing 2.Nc3 first before continuing 3.f4. The modern main line runs 2.Nc3 Nc6 3.f4 g6 4.Nf3 Bg7. The move 2.Nc3 has been played at high-level grandmaster chess (Gelfand and Short have played it) but only rarely. However a natural developing move like Nc3 can hardly be bad. Here White can play the positional 5.Bb5, threatening to double Black's pawns with Bxc6, or the more aggressive 5.Bc4, aiming for a kingside attack. A less common option is 2... e6, as La Bourdonnais played against McDonnell.
  • 2.d4 cxd4 3.c3 is the Smith-Morra Gambit
    Smith-Morra Gambit
    In chess, the Smith–Morra Gambit is an opening gambit against the Sicilian Defence distinguished by the moves:The Smith–Morra is not common in grandmaster games, but at club level chess it can be an excellent weapon.-History:...

    . Declining it by either 3....Nf6 or 3....d5, transposing to the c3 line, is possible, but accepting it by 3...dxc3 is critical. After 4.Nxc3, it is doubtful that White has enough compensation for the pawn; however, it can be dangerous for Black if he is unprepared, as there are many pitfalls for the unwary.
  • 2.Ne2 (the Keres Variation), was a favourite of Paul Keres
    Paul Keres
    Paul Keres , was an Estonian chess grandmaster, and a renowned chess writer. He was among the world's top players from the mid-1930s to the mid-1960s....

    , and has similar ideas to the Chameleon System discussed under 2.Nc3 – White can follow up with 3.d4 with an Open Sicilian, 3.g3 with a Closed Sicilian, or 3.Nbc3, continuing to defer the choice between the two.
  • 2.d3 signals White's intention to develop along King's Indian Attack
    King's Indian Attack
    The King's Indian Attack , also known as the Barcza System , is a chess opening system for White, most notably used by Bobby Fischer. Its typical formation is shown in the diagram to the right....

     lines, and usually transposes to the Closed Sicilian.
  • 2.b3 followed by 3.Bb2 is the Snyder Variation, named for USCF
    United States Chess Federation
    The United States Chess Federation is a non-profit organization, the governing chess organization within the United States, and one of the federations of the FIDE. The USCF was founded in 1939 from the merger of two regional chess organizations, and grew gradually until 1972, when membership...

     master
    Chess master
    A chess master is a chess player of such skill that he/she can usually beat chess experts, who themselves typically prevail against most amateurs. Among chess players, the term is often abbreviated to master, the meaning being clear from context....

     Robert M. Snyder. It has been used occasionally by Nigel Short
    Nigel Short
    Nigel David Short MBE is an English chess grandmaster earning the title at the age of 19. Short is often regarded as the strongest English player of the 20th century as he was ranked third in the world, from January 1988 – July 1989 and in 1993, he challenged Garry Kasparov for the World Chess...

     and is a favourite of Georgian
    Georgia (country)
    Georgia is a sovereign state in the Caucasus region of Eurasia. Located at the crossroads of Western Asia and Eastern Europe, it is bounded to the west by the Black Sea, to the north by Russia, to the southwest by Turkey, to the south by Armenia, and to the southeast by Azerbaijan. The capital of...

     GM Tamaz Gelashvili
    Tamaz Gelashvili
    Tamaz Gelashvili is a chess grandmaster from Georgia. He was awarded the Grandmaster title in 1999. His highest FIDE rating has been 2623, achieved in October 2007. His national ranking is fourth and he has played for...

    .
  • 2.g3 (the Steinitz Variation), which was sometimes also played by Taimanov, can transpose to the Closed Sicilian but offers other options such as 2...d5 3.exd5 Qxd5 for Black, and a central buildup with c3 and d4 for White.
  • 2.c4 occasionally leads to positions that resemble lines in the English Opening
    English Opening
    In chess, the English Opening is the opening where White begins:A flank opening, it is the fourth most popular and, according to various databases, anywhere from one of the two most successful to the fourth most successful of White's twenty possible first moves. White begins the fight for the...

    .
  • 2.b4 is the Wing Gambit
    Wing Gambit
    In chess, Wing Gambit is a generic name given to openings in which White plays an early b4, deflecting an enemy pawn or bishop from c5 so as to regain control of d4, an important central square...

    . White's idea is 2. b4 cxb4 3. a3, hoping to deflect Black's c-pawn, then dominate the center with an early d4. However, Black can gain an advantage with accurate play. The Wing Gambit is thus generally considered too reckless. GM Joe Gallagher
    Joseph Gallagher
    Joseph Gerald Gallagher is a British Chess Grandmaster and former British Champion, as well as a chess author.Born to Irish parents Norah and Patrick, Gallagher was the eldest child . His sister Marie also played chess to an international standard at age 11...

     calls it "a forgotten relic, hardly having set foot in a tournament hall since the days of Frank Marshall and Rudolph Spielmann. White sacrifices a pawn for ... well, not a lot."
  • 2.a3 is similar to the Wing Gambit
    Wing Gambit
    In chess, Wing Gambit is a generic name given to openings in which White plays an early b4, deflecting an enemy pawn or bishop from c5 so as to regain control of d4, an important central square...

    , the idea being to play 3.b4 next move.
  • 2.Na3 is an eccentric move recently brought into prominence by GM Vadim Zvjaginsev
    Vadim Zvjaginsev
    Cifuentes-Parada-Zvjaginsev, Wijk aan Zee Open 1995 1.d4 e6 2.Nf3 d5 3.c4 Nf6 4.Nc3 c6 5.e3 Nbd7 6.Qc2 b6 7.Be2 Bb7 8.O-O Be7 9.Rd1 O-O 10.e4 dxe4 11.Nxe4 Qc7 12.Nc3 c5 13.d5 exd5 14.cxd5 a6 15.Nh4 g6 16.Bh6 Rfe8 17.Qd2 Bd6 18.g3 b5 19.Bf3 b4 20.Ne2 Ne4 21.Qc2 Ndf6 22.Ng2 Qd7 23.Ne3 Rad8 24.Bg2? ...

     at the 2005 Russian Chess Championship Superfinal. He used it thrice during the tournament, drawing twice and beating Alexander Khalifman
    Alexander Khalifman
    Alexander Valeryevich Khalifman is a Soviet and Russian chess Grandmaster of Jewish descent; he is also a former FIDE champion.When Khalifman was 6 years old, he was taught chess by his father....

    .
  • 2.Bc4 (the Bowlder Attack), though once played at the highest level, is popular today only among club players or beginners who are unfamiliar with the Sicilian and are looking either to attack the weak f7 pawn or to prepare for a quick kingside castle. However, after a move such as 2...e6, Black will soon play ...d5 and open up the centre while gaining time by attacking the bishop. Anderssen
    Adolf Anderssen
    Karl Ernst Adolf Anderssen was a German chess master. He is considered to have been the world's leading chess player in the 1850s and 1860s...

    –Wyvill, London 1851 continued 2..e6 3.Nc3 a6 4.a4 Nc6 5.d3 g6 6.Nge2 Bg7 7.0-0 Nge7 8.f4 0-0 9.Bd2 d5 10.Bb3 Nd4 11.Nxd4, and now Soltis
    Andrew Soltis
    Andrew Eden Soltis is a chess Grandmaster, author and columnist.He won at Reggio Emilia 1971–72 and was equal first at New York 1977. He was awarded the International Master title in 1974 and became a Grandmaster in 1980...

     recommends 11...cxd4! 12.Ne2 Bd7!
  • 2.Be2 is the so-called Slow Variation.
  • 2.Qh5, threatening the c-pawn has been played a few times by Hikaru Nakamura
    Hikaru Nakamura
    Hikaru Nakamura is an American chess Grandmaster . He has been ranked among the top six players in the world by FIDE....

    , but the move is dubious. Simply 2...Nf6 gives Black a comfortable position after 3.Qxc5 Nxe4, while 3.Qh4 displaces the queen and loses time. Nakamura lost in 23 moves to Andrei Volokitin
    Andrei Volokitin
    Andriy Volokitin is a Ukrainian chess player and International Grandmaster of Chess.As a junior, he was twice a medallist at the World Youth Chess Championship, taking silver in 1998 at Oropesa del Mar at under-12 level, and bronze at the same venue a year later in the under-14 category...

     in 2005, and Neil McDonald criticised the opening experiment as "rather foolish".

ECO codes

The Encyclopaedia of Chess Openings
Encyclopaedia of Chess Openings
The Encyclopaedia of Chess Openings is a classification system for the opening moves in a game of chess. It is presented as a five volume book collection describing chess openings...

classifies the Sicilian Defence under the codes B20 through B99, giving it more codes than any other opening. In general these guidelines apply:
  • Codes B20 through B29 cover lines after 1.e4 c5 where White does not play 2.Nf3, and lines where White plays 2.Nf3 and Black responds with a move other than 2...d6, 2...Nc6 or 2...e6.
  • Codes B30 through B39 cover the lines beginning 1.e4 c5 2.Nf3 Nc6 that do not transpose into lines that can also begin with 2...d6. The most important variations included here are the Rossolimo, Kalashnikov, Sveshnikov and Accelerated Dragon.
  • Codes B40 through B49 cover the lines beginning 1.e4 c5 2.Nf3 e6, most importantly the Taimanov and Kan variations.
  • Codes B50 through B59 cover the lines after 1.e4 c5 2.Nf3 d6 not covered in codes B60–B99. This includes the Moscow Variation (3.Bb5+), 3.d4 cxd4 4.Qxd4, and lines in the Classical Variation except for the Richter–Rauzer Attack, including the Sozin Attack and the Boleslavsky Variation.
  • Codes B60 through B69 cover the Richter–Rauzer Attack of the Classical Variation.
  • Codes B70 through B79 cover the normal (unaccelerated) Dragon Variation.
  • Codes B80 through B89 cover the Scheveningen Variation.
  • Codes B90 through B99 cover the Najdorf Variation.

Further reading

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