The massive M-12 Self-Propelled Gun was developed in 1943, and fielded in 1944. Utilizing a 155-man Cannon designed in World War I (The Model 1917), which in turn was mounted to the chassis if the tried and true M-4 Tank. Weighing 40-tons, the 155mm Cannon fired a variety of 95-pound shells up to 15-miles. Using 9-cylinders, it had a ground speed of 23 mph. For protection, the front of the chassis had 1-inch of Armor plate, with side plates measuring .04-inch. The effective range of The M-12 was tested after The Allied Invasion of France (1944), when batteries of M-12 were emplaced along The Rhine River for bombardment of German targets. The M-12 and it's variants ushered in a new Era of Self-Propelled Artillery seen deployed during American conflicts in Korea and Southeast Asia.