The 155-mm Gun Motor Carriage M12 was a U.S. self-propelled gun developed during the Second World War. Only 100 were built; sixty in 1942 and another forty in 1943. The M12 was built on the chassis of the M3 Lee tank. It had an armored driver's compartment, but the gun crew were located in an open topped area at the back of the vehicle. An earth spade at the rear was employed to absorb recoil. During 1943 the vehicles were used for training or put into storage. Before the invasion of France, seventy four M12s were upgraded in preparation for combat operations. They were employed successfully throughout the campaign in North-West Europe. Although designed primarily for indirect fire, during assaults on heavy fortifications the M12s were sometimes employed in a direct-fire role. Limited storage space meant that only ten projectiles and propellant charges could be carried on the vehicle. Given this, a similar vehicle without the gun was produced as the Cargo Carrier M30. This was designed to transport the gun crew and additional ammunition. In operational conditions the M12 and M30 would serve in pairs. The M30, which could carry forty rounds of 155-mm ammunition, was armed with a .50-caliber Browning M2 machine gun. Created in 1944, this technical manual reveals a great deal about the M12's and M30's design and capabilities. Intended as a manual for those charged with operation and maintenance, it details many aspects of the M12's engine, cooling, power, suspension and other systems. Originally labeled restricted, this manual was declassified long ago and is here reprinted in book form. Please note, this text was not produced in large numbers and this replica may have some pages that are substandard in quality. Care has been taken however to preserve the integrity of the text.