This vehicle resulted from an urgent requirement to have some form of tank destroyer available until the M10 GMC could enter service. The M3 Gun Motor Carriage Halftrack used an M3 Halftrack modified to carry an M1897A4 field gun. Production began in late 1941, and in December of that year 50 arrived in the Philippines where they were used as SP artillery until the fall of Bataan. Altogether 2,202 were built, but 1,360 were later converted to M3Al Halftracks. In the PTO the M3 GMC was used successfully by the USMC (who often referred to it as the “SPM” [Self-Propelled Mount]) until the war’s end, with each infantry regiment in a Marine division having a platoon of two (four after April 1944) in its weapons company, and until that same date the divisional Special Weapons battalion also had three such platoons. The M3 GMC was the only type of halftrack employed in Marine divisions. In Tunisia the M3 GMC was used in the 601st, 70lst, 805th, 813th, and 894th TD Battalions (Heavy SP), with four per platoon. They met with mixed success in that campaign; their thin armor caused many to be knocked out, but when properly used in ambushes from HD positions they were effective vs Axis armor. M3 GMC were also used in Sicily by the 601st TD Battalion.