German weather ship Lauenburg
Encyclopedia
The Lauenburg was a German weather ship
used in the early years of the Second World War to provide weather reports for German shipping, particularly German U-boats. Her capture and subsequent sinking on 28 June 1941 allowed the Royal Navy
to acquire important German code books and parts of an Enigma machine
, and came after the German use of such vessels had been identified as a weakness that could be exploited to break the Enigma code.
. She was acquired by the Kriegsmarine
in 1940, and entered naval service in November that year, having been converted into a weather ship, but retaining the name Lauenburg. In her new guise she carried a crew of between 19 and 21, as well as eight meteorologists. She was to be used to provide detailed weather reports for naval units, including Germany's U-boat
fleet.
cryptologist Harry Hinsley
, then working at Bletchley Park
realised at the end of April 1941 that the German weather ships, usually isolated and unprotected trawlers, were using the same Enigma
code books as were being used on the heavily armed U Boats. The trawlers, which were transmitting weather reports to the Germans, were in turn being sent naval Enigma messages.
Although the weather ships did not transmit enciphered weather reports on Enigma machines, they still needed to have one of the machines on board if they were to decode the Enigma signals transmitted to them. Hinsley realised that if the code books could be captured from one of these vulnerable trawlers, the naval Enigma system could be broken, with British intelligence able to decipher messages to U-boats and discover their locations. The problem remained that if the navy were to attempt to capture one of the weatherships, the German crew would have time to throw their current Enigma settings into the sea before they were boarded. Hinsley instead reasoned that the following month's Enigma settings would be locked in a safe aboard the ship, and could potentially be overlooked if the Germans were forced to hastily abandon ship. On being informed, the Admiralty
despatched seven destroyers and cruisers to the northeast of Iceland
at the beginning of May 1941. The target was the München, one of the weather ships operating in the area. In the course of the raid, the weather ship, and the Enigma settings for June 1941 were captured. As a result, naval Enigma messages transmitted during June 1941 could be quickly deciphered.
Halfway through June 1941 the Germans replaced the bigram
tables used in Enigma. This would have resulted in a codebreaking blackout unless further settings could be captured. Hinsley and the Admiralty were concerned that capturing another weather ship might alert the Germans to their vulnerability and cause them to immediately alter them again. It was eventually decided to take the risk and on 25 June 1941 four warships, the light cruiser
HMS Nigeria
and the destroyers HMS Tartar
, HMS Jupiter
and HMS Bedouin
, were despatched from Scapa Flow
to capture the codebooks from the Lauenburg, another weather ship operating north of Iceland, which Hinsley had selected.
, and Tartar began firing. The Lauenburg's crew quickly abandoned the ship in two lifeboats. Minutes later, Tartar steamed alongside and a boarding party seized the Lauenburg. A large amount of material was collected and transferred to the Tartar. The allied warships then fired on and sank the Lauenburg.
The recovered material allowed further understanding of the Enigma codes and resulted in faster decoding of encrypted messages, as well as providing an up-to-date set of codes.
Weather ship
A weather ship was a ship stationed in the ocean as a platform for surface and upper air meteorological observations for use in weather forecasting. They were primarily located in the north Atlantic and north Pacific oceans, reporting via radio...
used in the early years of the Second World War to provide weather reports for German shipping, particularly German U-boats. Her capture and subsequent sinking on 28 June 1941 allowed the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
to acquire important German code books and parts of an Enigma machine
Enigma machine
An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by German engineer Arthur Scherbius at the end of World War I...
, and came after the German use of such vessels had been identified as a weakness that could be exploited to break the Enigma code.
Early life
The Lauenburg had been built in 1938 as a fishing trawler, named after the town of Lauenburg, and with the identification number 'PG 532'. She operated out of Geestemünde for her owners, H. Bischoff & Co, of BremenBremen
The City Municipality of Bremen is a Hanseatic city in northwestern Germany. A commercial and industrial city with a major port on the river Weser, Bremen is part of the Bremen-Oldenburg metropolitan area . Bremen is the second most populous city in North Germany and tenth in Germany.Bremen is...
. She was acquired by the Kriegsmarine
Kriegsmarine
The Kriegsmarine was the name of the German Navy during the Nazi regime . It superseded the Kaiserliche Marine of World War I and the post-war Reichsmarine. The Kriegsmarine was one of three official branches of the Wehrmacht, the unified armed forces of Nazi Germany.The Kriegsmarine grew rapidly...
in 1940, and entered naval service in November that year, having been converted into a weather ship, but retaining the name Lauenburg. In her new guise she carried a crew of between 19 and 21, as well as eight meteorologists. She was to be used to provide detailed weather reports for naval units, including Germany's U-boat
U-boat
U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...
fleet.
The weather ships and Enigma
The BritishUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
cryptologist Harry Hinsley
Harry Hinsley
Sir Francis Harry Hinsley OBE was an English historian and cryptanalyst. He worked at Bletchley Park during the Second World War and wrote widely on the history of international relations and British Intelligence during the Second World War...
, then working at Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
realised at the end of April 1941 that the German weather ships, usually isolated and unprotected trawlers, were using the same Enigma
Enigma machine
An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by German engineer Arthur Scherbius at the end of World War I...
code books as were being used on the heavily armed U Boats. The trawlers, which were transmitting weather reports to the Germans, were in turn being sent naval Enigma messages.
Although the weather ships did not transmit enciphered weather reports on Enigma machines, they still needed to have one of the machines on board if they were to decode the Enigma signals transmitted to them. Hinsley realised that if the code books could be captured from one of these vulnerable trawlers, the naval Enigma system could be broken, with British intelligence able to decipher messages to U-boats and discover their locations. The problem remained that if the navy were to attempt to capture one of the weatherships, the German crew would have time to throw their current Enigma settings into the sea before they were boarded. Hinsley instead reasoned that the following month's Enigma settings would be locked in a safe aboard the ship, and could potentially be overlooked if the Germans were forced to hastily abandon ship. On being informed, the Admiralty
Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...
despatched seven destroyers and cruisers to the northeast of Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
at the beginning of May 1941. The target was the München, one of the weather ships operating in the area. In the course of the raid, the weather ship, and the Enigma settings for June 1941 were captured. As a result, naval Enigma messages transmitted during June 1941 could be quickly deciphered.
Halfway through June 1941 the Germans replaced the bigram
Bigram
Bigrams or digrams are groups of two written letters, two syllables, or two words, and are very commonly used as the basis for simple statistical analysis of text. They are used in one of the most successful language models for speech recognition...
tables used in Enigma. This would have resulted in a codebreaking blackout unless further settings could be captured. Hinsley and the Admiralty were concerned that capturing another weather ship might alert the Germans to their vulnerability and cause them to immediately alter them again. It was eventually decided to take the risk and on 25 June 1941 four warships, the light cruiser
Light cruiser
A light cruiser is a type of small- or medium-sized warship. The term is a shortening of the phrase "light armored cruiser", describing a small ship that carried armor in the same way as an armored cruiser: a protective belt and deck...
HMS Nigeria
HMS Nigeria (60)
HMS Nigeria was a Crown Colony-class light cruiser of the British Royal Navy completed early in World War II and served throughout that conflict. She was named for the British territory of Nigeria.-Home waters:...
and the destroyers HMS Tartar
HMS Tartar (F43)
HMS Tartar was a Tribal-class destroyer of the Royal Navy that saw service in most of the naval theatres of World War II. She had an eventful career, eventually receiving the nickname 'Lucky Tartar' due to her numerous escapes from dangerous situations...
, HMS Jupiter
HMS Jupiter (F85)
HMS Jupiter was a J-class destroyer of the Royal Navy laid down by Yarrow & Company at Scotstoun in Glasgow on 28 September 1937, launched on 27 October 1938 and commissioned on 25 June 1939.-Operations:...
and HMS Bedouin
HMS Bedouin (F67)
HMS Bedouin was a Tribal-class destroyer of the British Royal Navy that saw service in World War II. She was launched on 21 December 1937 by William Denny and Brothers....
, were despatched from Scapa Flow
Scapa Flow
right|thumb|Scapa Flow viewed from its eastern endScapa Flow is a body of water in the Orkney Islands, Scotland, United Kingdom, sheltered by the islands of Mainland, Graemsay, Burray, South Ronaldsay and Hoy. It is about...
to capture the codebooks from the Lauenburg, another weather ship operating north of Iceland, which Hinsley had selected.
The capture of the Lauenburg
At around 7pm on 28 June, a lookout aboard HMS Tartar sighted the Lauenburg off Jan MayenJan Mayen
Jan Mayen Island is a volcanic island in the Arctic Ocean and part of the Kingdom of Norway. It is long and 373 km2 in area, partly covered by glaciers . It has two parts: larger northeast Nord-Jan and smaller Sør-Jan, linked by an isthmus wide...
, and Tartar began firing. The Lauenburg's crew quickly abandoned the ship in two lifeboats. Minutes later, Tartar steamed alongside and a boarding party seized the Lauenburg. A large amount of material was collected and transferred to the Tartar. The allied warships then fired on and sank the Lauenburg.
The recovered material allowed further understanding of the Enigma codes and resulted in faster decoding of encrypted messages, as well as providing an up-to-date set of codes.
See also
- Cryptanalysis of the EnigmaCryptanalysis of the EnigmaCryptanalysis of the Enigma enabled the western Allies in World War II to read substantial amounts of secret Morse-coded radio communications of the Axis powers that had been enciphered using Enigma machines. This yielded military intelligence which, along with that from other decrypted Axis radio...
- North Atlantic weather warNorth Atlantic weather warThe North Atlantic weather war occurred during World War II. The allies and Germany vied for access to reliable weather data in the North Atlantic and Arctic Oceans and sought to deny the other weather information. Meteorological data was important as it affected military planning and the routing...