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Canon de 75 modèle 1897
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The French 75mm field gun was a quick-firing field artillery piece adopted in March 1898 after 5 years of research and secret trials.
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The French 75mm field gun was a quick-firing field artillery piece adopted in March 1898 after 5 years of research and secret trials. It saw widespread service in World War I including in the American Expeditionary Forces ( AEF ). It also served during World War II in various but more limited capacities . It was commonly known as the French 75, simply the 75 and Soixante Quinze (French for 75). Its official French designation was : Materiel de 75mm Mle 1897 . It introduced, for the first time in the history of field artillery, a hydro-pneumatic long recoil mechanism which kept the gun's trail and wheels perfectly still during the firing sequence. Since it did not need to be re-aimed after each shot the French 75 could deliver fifteen rounds per minute on its target, either shrapnel or high-explosive, up to about 5 miles ( 8,500 meters) away.
The French 75 was entirely researched, developed and manufactured at State-controlled arsenals, principally at Atelier de Construction de Puteaux ( APX ) near Paris for its hydro-pneumatic recoil mechanism . Other parts of the gun were sub-contracted to other arsenals including MAS (an abbrevation of Manufacture d'Armes St. Etienne ) Tarbes and Bourges. It is not to be confused with the Schneider manufactured "Canon de 75mm Mle 1912" used by French cavalry and the Serbian army, and its 1914 modification. Although they used the original French 75's ammunition, these privately manufactured Schneider guns were lighter, smaller, and mechanically different.
Development
The forerunner of the French 75 was an experimental 57mm gun which was first assembled in September 1891 at the Bourges arsenal under the direction of a Captain Sainte-Claire Deville. This 57mm gun assembled a number of the most advanced artillery techniques available at the time:
- 1) Vieille's smokeless powder, invented in 1884.
- 2) Self-contained ammunition: the powder charge sat in a brass case which also held the shell.
- 3) An early hydro-pneumatic short recoil mechanism designed by Major Louis Baquet.
- 4) A rotating screw breech, soon to appear on the 75mm field gun, built under license from Thorsten Nordenfelt.
Somewhat earlier, in 1890, General Mathieu, Director of Artillery at the Ministry of War, had been informed that Konrad Haussner, a German engineer working at the Ingolstadt arsenal had patented an oil and compressed air long recoil system for field artillery. Furthermore, that after a series of tests made by the firm of Krupp the latter considered manufacturing a new gun incorporating this system. However Krupp finally rejected Haussner's invention due to insoluble technical problems caused by hydraulic fluid leakage. Then Konrad Haussner sold his patents in 1891 to a firm named Gruson which searched for other potential buyers. After reviewing the patent office blueprints in February 1892, the French artillery engineers did recommend to proceed on their own without purchasing the Haussner invention. Accordingly, General Mathieu turned to Lt. Colonel Albert Deport, at the time the Director of the Atelier de Construction de Puteaux (APX), and asked him whether he could construct a gun on the general principle of the Haussner long cylinder recoil without infringing the existing patents. This request to proceed, being accepted as feasible, was made formal on July 13, 1892.
It took five more years under the overall leadership of Mathieu's successor, General Deloye, to perfect and finally adopt in March 1898 an improved and final version of the Deport 75mm long-recoil field gun. Various deceptions, some of them linked to the Dreyfus Case, had been implemented by General Deloye and French counter-intelligence to distract German espionage.
An experimental version of Deport's 75mm field gun was first tested during the summer of 1894. Extensive trials, however, revealed that it was still prone to hydraulic fluid leakage from the long recoil mechanism. Although judged promising, the Deport 75 was returned to Puteaux arsenal for further improvements. Hydraulic fluid leakage was typical of this experimental phase of artillery development during the 1890's, as Haussner and Krupp had previously experienced.
In December 1894, Lt. Colonel Albert Deport (1846-1929) was passed over for promotion and resigned to join a private armaments firm. Two young engineers who had worked under him, Captains Etienne Sainte-Claire Deville (1857-1944) and Emile Rimailho (1864-1954), carried on with the project and brought it to fruition in 1896. Their contribution was a leak-proof hydro-pneumatic long recoil mechanism which they named " Frein II " ( Brake # II ). A major progress was the placement of improved silver alloy rings on the freely moving piston inside the main hydro-pneumatic cylinder. These and other modifications achieved the desired result : the long term retention of hydraulic fluid and compressed air inside the recoil system, even under the worst field conditions. Captain Sainte-Claire Deville also designed important additional features such as a device for piercing the fuzes of shrapnel shells automatically during the firing sequence (an "automatic fuze-setter"), thus determining the desired bursting distance. The independent sight had also been perfected for easy field use by the crews and a nickel-steel shield protected the gunners. The armored caissons were designed to be tilted in order to present the shells horizontally to the crews. The wheel brakes could be swung under each wheel ("abattage") and together with the trail spade they immobilized the gun during firing. The gun was adopted on March 28, 1898 under the official name of "Materiel de 75mm Mle 1897". The public saw it for the first time during the Bastille Day parade of July 14, 1899 but no one then had any idea of the technical progresses that had been achieved.
Description of the hydro-pneumatic recoil mechanism
The gun's barrel did slide back on rollers, including a set at the muzzle, when the shot was fired. The barrel was attached near the breech to a piston rod extending into an oil-filled cylinder placed just underneath the gun. When the barrel recoiled, the piston was pulled back by the barrel's recoil and thus pushed the oil through a small orifice and into a second cylinder placed underneath. That second cylinder contained a freely floating piston which separated the surging oil from a confined volume of compressed air . During the barrel's recoil the floating piston being pressed forward by the surging oil, compressed the air even further inside the confined volume. This action absorbed the recoil progressively as the internal air pressure rose and , at the end of recoil, generated a strong but decreasing back pressure that returned the gun forward to its original position. The smoothness of this system had no equal in 1897 and for at least another ten years. Each recoil cycle on the French 75, including the return forward , lasted about 2 seconds thus permitting a maximum attainable firing rate of 30 rounds per minute .
Ammunition
The French 75 fired two types of shells, with a muzzle velocity of and a maximum range of . Because of these characteristics, the shell's trajectories were fairly flat. The French 75 had not been designed for high angle plunging fire.
- A impact-detonated, thin-walled steel, high-explosive (HE) shell with a time delay fuse. The delay lasted five hundredths of a second, designed to explode at a man's height after bouncing forward off the ground. A melted explosive called trinitrophenol, picric acid, or "Melinite", used since 1888 by French artillery, filled the HE shell.
- A time-fused shrapnel shell containing 290 lead balls. The balls shot forward when the fuse's timer reached zero, ideally bursting high above the ground and enemy troops. Later, during World War I, several new shells and fuses were introduced due to the demands of trench warfare, including a boat-tailed shell that could reach out to . Every shell, whether it be a high explosive or shrapnel shell, was fixed to a brass case which automatically ejected when the breech opened.
Rapid fire capability
The French 75 introduced a new concept in artillery technology: rapid firing without realigning the gun after each shot. The old artillery had to be resighted after each shot in order to stay on target and thus fired no more that two aimed shots per minute. The French 75 easily delivered fifteen aimed rounds per minute and could fire even faster for short periods of time. This rate of fire, the gun's accuracy, and the lethality of the ammunition against personnel, made the French 75 superior to all other regimental field artillery at the time. When made ready for action, the first shot buried the trail spade and the two wheel anchors into the ground, following which all other shots were fired from an entirely stable platform. Bringing down the wheel anchors tied to the braking system ( visible on the Invalides Museum picture shown to the left of this paragraph ) was called "abattage". The gun was unable to elevate beyond eighteen degrees, unless the trail spade had been deeply lowered into the ground, however the 75mm field gun was not designed for plunging fire. The gun could be traversed laterally 3 degrees to the right or 3 degrees to the left by sliding the trail on the wheel's axle. Progressive traversing together with small changes in elevation could be carried out while continuously firing time fused shrapnel, or high-explosive shells, resulting in sweeping vast areas free of enemy troops. For example, a 4 gun battery firing shrapnel could deliver 17,000 ball projectiles over an area 100 meters wide by 400 meters long in a single minute . This firing procedure was called " fauchage" or sweeping fire. Because of the gun's traversing ability without moving the wheels, the longer the distance to the enemy concentration the wider was the area that could be swept.
World War I Service
The French artillery entered the war in August 1914 with more than 4,000 Mle 1897 75mm field guns (1,000 batteries of 4 guns each). Each Mle 1897 75mm field gun battery ( 4 guns )was manned by highly trained crews led by 4 officers recruited among graduates of engineering schools. Enlisted men from the countryside took care of the 6 horses that pulled each gun and its first limber. Another 6 horses pulled each additional limber and caisson which were assigned to each gun. A battle ready French 75 battery was manned by 170 men and included 160 horses, most of them pulling ammunition as well as repair and supply caissons. Over 17,500 Mle 1897 75mm field guns were produced during WWI, over and above the 4,100 French 75's which were already deployed by the French Army in August 1914.
All the essential parts, including the gun's barrel and the oleo-pneumatic recoil mechanisms were manufactured by French State arsenals: Puteaux, Bourges, Chatellerault and St Etienne. A truck-mounted anti-aircraft version of the French 75 was assembled by the automobile firm of De Dion-Bouton and adopted in 1913.
The total production of 75mm shells during WWI exceeded 200 million rounds, mostly by private industry. In order to ramp-up shell production from 20,000 rounds per day to 100,000 in 1915, the government turned to civilian contractors and, as a result, shell quality deteriorated. This led to an epidemic of burst barrels which afflicted 75mm artillery during 1915. Colonel Sainte-Claire Deville confronted the crisis (defects in the base of the shells, due to shortcuts in manufacturing) and the problems were corrected. Shell quality came back by September 1915, but never to the full exacting standards of pre-war manufacture.
The French 75 gave its best performances during the Battle of the Marne in August-September 1914 and at Verdun in 1916. The contribution of 75mm artillery in these two battles, and thus to the French victories that ensued, was perceived at the time as quantitatively important. In the case of Verdun, over 1,000 French 75's (250 batteries) were constantly in action, night and day, on the battlefield during a period of nearly nine months. The total consumption of 75mm shells at Verdun during the period February 21 to September 30,1916, is documented by the public record at Service Historique de l'Armee de Terre to have been in excess of 16 million rounds, or nearly 70% of all shells fired by French artillery during that battle. The French 75 was a devastating anti-personnel weapon against waves of infantry attacking in the open, as at the Marne and Verdun. However its shells were comparatively light and lacked the power to obliterate trench works, concrete bunkers and deeply buried shelters. Thus,eventually, the French 75 batteries became routinely used to cut corridors, with high-explosive shells, across the belts of German barbed wire. Finally, after 1916, the 75 batteries became the carriers of choice to deliver toxic gas shells, including mustard gas and phosgene.
The French Army had to wait until 1917 to receive the modern heavy field artillery ( e.g. the 155 mm Schneider howitzer and the long range Canon de 155mm GPF) that was virtually absent in 1914. In the meantime it had to do with the old de Bange 155mm converted siege artillery, without recoil brakes, that was inferior in rate of fire and mobility to the modern and more numerous German heavies. The excessive reliance on the 75mm field gun, a doctrine developed by the General Staff during the pre-war years, cost hundreds of thousands of French lives that were lost during the unsuccessful Joffre offensives ( Artois/Champagne) that took place during the year 1915.
World War II Service
Despite obsolescence brought on by new developments in artillery design, large numbers of 75s were still in existence in 1939 (4,500 in the French army alone) and they eventually found their way into a number of unlikely places. Some had been delivered to Poland in the 1920's, together with infantry ordnance, in order to fight the Bolsheviks. They were known as 75mm Armata Polowa wz.1897/17. In 1939 the Polish army had 1374 of these guns, making it by far the most numerous artillery piece in Polish service.
Some French guns were modernised between the wars, in part to adapt it for anti-tank fire, resulting in the Canon de 75 Mle 1897/33 which fired a special armor piercing shell. Many were captured by Germany during the Fall of France in 1940, in addition to many Polish guns captured in 1939. Over 600, renamed 7.5 cm PaK 97/38, were mounted on a 5 cm PaK 38 carriage and put to use by the Wehrmacht in 1942 as an emergency weapon against the Soviet Union's T-34 and KV tanks. Its relatively low velocity and a lack of updated armor piercing ammunition limited its effectiveness as an anti-tank weapon. When the German 7.5 cm PaK 40 became available in sufficient numbers, most remaining PAK 97/38 pieces (modified French 75's)were returned to France to reinforce the Atlantic Wall defenses.
British Service
In 1915 Britain acquired a number of "autocanon de 75 mm mle 1913" anti-aircraft guns, as a stopgap measure while it developed its own anti-aircraft alternatives. They were used in the home defence of Britain, usually mounted on de Dion motor lorries using the French mounting which the British referred to as the "Breech Trunnion". Britain also purchased a number of the standard 75 mm guns for which the Coventry Ordnance Works developed a mounting, the "Centre Trunnion", for AA use on British vehicles. At the Armistice there were 29 guns in service in Britain.
US Service
The US Army adopted the French 75 mm field gun during World War I and used it extensively in battle. There were 480 American 75mm field gun batteries (over 1,900 guns) on the battlefields of France in November 1918 (Crowell,1919). The US Army also kept a large inventory of the gun after WW-1 and used it extensively for training purposes until 1942. The first US artillery shots in action were fired by Battery C, 6th Field Artillery on October 23 1917 with a French 75 named "Bridget" which is preserved today at the United States Army Ordnance Museum. Manufacturing of the French 75 by American industry began in the Spring of 1918 and quickly built up to an accelerated pace ( Crowell ,1919 ).Carriages were built by Willys-Overland,the hydro-pneumatic recuperators by Singer Manufacturing Co and Rock-Island Arsenal,the cannon itself by Symington-Anderson and Wisconsin Gun Company. One thousand and fifty (1,050) French 75s were built by American industry during WW-1 but only 143 had been shipped to France by November 11,1918.
During the 1930's many of those were equipped with rubber tires. Others were mounted on a split trail permitting plunging fire: the French 75 M2A1,A2 and A3. Furthermore, M3 Half-Track mounted French 75's (M3 GMC) were used in the Pacific theater for quite a while, following Pearl Harbor, and later during the landing operations in North Africa and Italy. One of the more ingenious uses for the old gun was its mounting in B-25 Mitchell bombers for attacking Japanese shipping. Otherwise the French 75 was replaced by the more powerful and more versatile U.S. 105mm M101 split-trail Howitzer by 1941.
Variants and derivatives
Field artillery
- canon de 75 mm mle 1897 modifié 1938
- motorized artillery variant with wooden wheels replaced by metallic wheels with tyres, altered shield
Mountain gun
Anti-aircraft
- autocanon de 75 mm mle 1913
- self-propelled anti-aircraft variant, on De Dion-Bouton chassis.
- canon de 75 mm contre-aéroplanes sur plateforme mle 1915
- static anti-aircraft variant on rotating platform
- canon de 75 mm contre-aéroplanes mle 1917
- anti-aircraft variant on 1-axle trailer with stabilizer legs.
Anti-tank
- Canon de 75 mm mle 1897 modifié 1933
- similar shield and wheels as the standard version, but split-trail carriage allowing 58° traverse. Used in the anti-tank role
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