Considered a combat tank during World War 1, the Char d'Assault St. Chamond shared qualities more akin to an "assault gun" of World War 2 - today categorized as "Self-Propelled Gun" (SPG). The St. Chamond was of French origin and saw combat through most of World War 1 after its introduction with the French Army in 1916. Despite the potential that tanks held on the battlefields of the period, the St. Chamond proved a heavy, plodding war instrument never truly capable of traversing even the most modest of terrain. Despite this operational limitation, the French were forward-thinking enough to provide the tracked vehicle with a powerful and reliable 75mm howitzer for ranged fire.
Design of the St. Chamond tank was headed by Colonel Emile Rimailho who utilized the running gear of the American Holt Tractor as a starting point (similar to the competing Schneider CA tank before it). The chassis and track system were retained and a cumbersome armored hull superstructure was erected atop the system to provide the requisite fighting compartment. The engine was centrally located in the hull with suspension was via coil springs. There was a driver's position at the front and the rear of the vehicle to allow for both forwards and backwards travel without having the tank turn completely around or have the front driver pilot blindly rearwards. Primary armament was a fixed, forward-firing 75mm main gun that featured limited elevation with up to 4 x 8mm Hotchkiss machine guns used to defend the tank from enemy infantry attacks. One machine gun was set to the right-front of the hull with another at the rear hull facing. Both sides of the hull were defensed by a machine gun - in effect providing all-around protection for the vehicle. Armor thickness measured up to 11mm.
Colonel Rimailho's participation in the design of the St. Chamond is of note here for his contributions to the French Army dated back to his time at the French state arsenal where he contributed to the development of the excellent Canon de 75mm modele 1897 field gun. When not properly compensated for his efforts, Rimailho left in protest and joined the team at Saint Chamond, designing its 75mm armament largely around the modele 1897. Thusly, the 75mm main gun featured in the original St. Chamond tank would follow the form and function of the French Army field gun to some extent - though being modified to suit the new role and cleared to fire existing French Army 75mm ordnance.
Power for the St. Chamond was supplied by through a single Panhard-Levassor 4-cylinder gasoline-fueled engine of 90 horsepower. This powerplant was then tied to an electrically-powered Crochat-Colardeau transmission system which, in turn, added unnecessary weight to the overall design. Electric generators were charged in supplying power to each individual track system allowing for 7.5mph speeds in ideal conditions. Range was limited to 37 miles.
The large St. Chamond tank required an operating crew of eight personnel to man the various onboard systems. The driver also served as the tank commander with vision out of a protruding upper hull fixture. He was seated at the front left of the vehicle. To his right was the main gun fitted centrally at the front hull. To the right of the main gun was a machine gunner who also doubled as the breech operator for the main gun. A second driver was positioned at the rear and called to action when the vehicle needed rearwards control. Additional machine gunners were stationed at the sides and rear of the design.
The initial St. Chamond prototype was made ready in September of 1916 with some 400 examples of the type already on order.
The most defining design characteristic of the St. Chamond was its oversized hull superstructure which spanned out over both the chassis front and rear. While this supplied the necessary internal volume needed for the gun, crew and engine, this naturally presented the tank with a very long hull that made crossing uneven terrain and trenches extremely difficult if not impossible. Once stuck, the St. Chamond would become nothing more than cannon fodder to German artillery or a sitting duck to grenade-toting German infantry. While the front hull sported some basic form of ballistics protection thanks to its angled face, the sides, rear and top of the vehicle were flat with little-to-no protection from artillery - the primary danger to tanks on the World War 1 battlefield. In addition to the detrimental hull design, the front-right machine gunner also managed the breech functions of the 75mm main gun which added unnecessary duties in the heat of battle (a dedicated gunner/loader managed the principle firing and elevation actions). The main gun, being fixed into its forward position, was limited in its elevation and therefore overall range and since the gun lacked any side-to-side traversal, the driver would have to turn the entire tank to face the target.
To make matters worse for the crew, the engine sat in an open-air fitting at the center of the design which divided the front and rear fighting compartments. Its open-air placement ensured that the fighting compartment would be noisy, smell of grease and oil and spew out fumes thusly making it a terrible work environment for the crew. Consider the fact that these were eight men required to spend hours on end in tight confines under the stress of battle. Walkways were set to either side of the engine to allow for crew allocation though these walkways were also home to the side machine gunners which complicated quick, effective internal maneuvering. One benefit of the open-air engine was easy access for make-shift repairs and maintenance in-the-field.
Once in service, the St. Chamond saw her armor increased from the original 11mm thickness to 19.5mm. The main gun designed by Rimailho was also dropped in favor of the standardized French Army modele 1897 series in 1917. A new roof design was implemented, intended to roll enemy grenades off of the tank while other protruding structures were eliminated for a much simpler, cleaner look. Early operational St. Chamond tanks had their armament removed and utilized for their hauling power in towing Schneider tanks.
The first "true" direct combat actions concerning St. Chamond tanks occurred on May 5th, 1917 to which three of the committed sixteen systems were lost in battle, others running aground over uneven terrain as expected. In limited operational service as a frontline combat tank, the St. Chamond failed to make an impression, ultimately given up in favor of the excellent French FT-17 two-man light tanks. Where the St. Chamond series did shine was in its assault prowess where her 75mm main gun could be brought to bear at distant targets. It was in this role that the St. Chamond would essentially become the assault gun that was never envisioned of her. The St. Chamond series would end the war as such while other chassis were relegated to supplementary roles, such as that of tracked supply carrier, until the armistice in November of 1918.
Some 377 St. Chamond tanks were completed during the war with only a single example remaining today - this on display at the Musee des Blindes in Saumur.