The multi-turret tank was something of a staple of the interwar period and influenced somewhat by the "Land Ship" approach of World War 1 (1914-1918). As such, the 1930s continued tradition with several nations investing in the development of such types including Britain, Germany, and the Soviet Union. The key Soviet development of the period became the multi-turret "T-35" Heavy Tank which was itself influenced by the British Vickers Independent. This gave a poor showing in the Spanish Civil War (1936-1939) namely due to poor armor protection so a subsequent program attempted to right-the-wrongs of the design. It was this venture that ultimately begat the famous "KV-1" series heavy tank for the Red Army - and also gave rise to two other (now largely forgotten) competing designs, the "T-100" (the focus of this article) and the SMK (detailed elsewhere on this site).
The T-100 and SMK were very similar to one another in appearance, utilizing a conventional track-and-wheel arrangement relying on multiple small road wheels, a rear-mounted engine, and an extended-length hull. However, the key physical quality of both was the two in line turrets with the primary turret seated over midships mounting a 76.2mm cannon and the secondary turret fitting a 45mm anti-tank gun closer to the bow. Originally, as many as five turrets were to be included but this requirement was dropped early in development (engineers were against the multi-turret approach to begin with). Both designs eventually used a torsion bar suspension system and multiple 7.62mm DT machine gun positions. Required armor protection was to be against 45mm shells at close-to-medium ranges and against 75mm shells at medium-to-long ranges. Armor, therefore, was welded in both offerings for maximum strength and protection to the crew and vital internal workings.
While only one of the SMK form was built, two of the T-100 were completed. This model featured a crew of up to eight men charged with various duties about the tank. The tank held a length of 27.5 feet, a beam of 11.1 feet, and a height of 11.2 feet. Power was from a single GAM-34BT 12-cylinder, liquid-cooled, gasoline-fueled engine developing 800 horsepower and allowing for road speeds of 22 miles per hour and operational ranges out to 120 miles (less so when going cross-country). The drive equipment included no fewer than eight double-tired road wheels to a hull side. The drive sprocket was mounted at the rear and the track idler at front. Five track-return rollers were used along the track run's upper reaches.
The primary gun became the Type L-11 weapon and to this was afforded 120 projectiles. The secondary fit was the proven Red Army 45mm ant-tank gun. Held in independently-operating turrets, the T-100 held qualities akin to a battleship with broad arcs of fire with each turret able to target separate enemies at once. The machine guns added an infantry defense measure for those elements attempting to rush the vehicle with explosives. With one turret fitted forward and the other at middle, joined by the engine at the rear, the vehicle was relatively well-balanced for its size but its length made it still clumsy and cumbersome while weight also increased - the T-100 tipping the scales at 58 tons.
Beyond the usual evaluations and trials, the T-100, along with the SMK, were both operationally fielded in the "Winter War" (November 1939 - March 1940) against neighboring Finland. SMK was disabled by an enemy landmine in December of 1939 and abandoned for two months before being recovered by the Soviets - it was never repaired nor reinstated. The T-100 had a slightly better showing in its exposure, the armor protection proving sound against Finnish 37mm and 45mm anti-tank guns. Despite this, it held terrible inherent traits for a frontline combat system and was not given official approval for adoption/serial production. At least one of the two T-100 pilot vehicles was modified to the Self-Propelled Gun (SPG) role in 1940 with a 130mm naval gun as its main armament (as the one-off "SU-100Y") to combat stout Finnish bunker fortifications. Out of desperation, this sole example was then pressed into service in the defense of Moscow (1941-1942) against the invading Germans.
The competing SMK design, despite also having been passed over by Soviet authorities, was simplified by its engineers into a single turret form and this is what went on to become the classic KV-1 Heavy Tank detailed elsewhere on this site.