In March 1944, the United States Army Ordnance Department authorized the conversion of two M18 tank destroyers as prime movers for the 3-inch Gun M5 on Carriage M6, a towed antitank gun used by tank destroyer battalions, and armored command and reconnaissance vehicles.

[1] The M39 was more widely used during the Korean War, where they were employed in variety of roles, including as troop transports, armored ambulances, and ammunition carriers for 155mm M41 Gorilla self-propelled howitzers.

M39s played a vital role in supplying and ferrying troops to isolated outposts during the later defensive phase of the Korean War, though their thin armor and open tops meant the crews were vulnerable to enemy fire, and the fully enclosed M75 armored personnel carrier eventually replaced it in this role.

Because the M39s carriers had .50 caliber machine guns, unlike the unit's M41 self-propelled howitzers, they led the retreating column.

During the retreat, it was ambushed by Chinese forces; in the battle, the unit lost seven killed in action, two M39 armored utility vehicles, and had two M41s damaged and 31 wounded.