M113 armored personnel carrier

Introduced in 1960 by the U.S. Army, the M113 is a lightly armored, fully tracked, box-shaped armored personnel carrier. It was intended as a "battle taxi" to take infantry to the edge of the battlefield, where they would dismount and fight on foot, perhaps alongside tank (military) tanks. While the battle taxi concept has been superceded by the infantry fighting vehicle approach in modern militaries, the M113 and derivatives still have applications outside the thick of battle. In combat less intensive than main armored engagements of Operation DESERT STORM, where the M2 Bradley infantry and M3 scout carriers took troops into action, the APC still is common. Thousands of M113-family vehicles were used in the Gulf War.

M113 vehicles are used worldwide; over 80,000 have been built.

Vietnam
When introduced into the Vietnam War, the Army of the Republic of Vietnam soon rejected the pure battle taxi doctrine. In their first combat use in September 1962, in knee-deep rice paddie in the Plain of Reeds, infantrymen took high casualties. They quickly concluded light metal and all-terrain tracks were superior to cloth uniforms and boots. Soon, not only was the ARVN staying in the APC as much as possible, but began to modify them for better survivability.

Originally, the M113 was armed with a single .50 caliber machine gun, fired by a gunner standing in a hatch. These soon went behind an armor shield, and two more .30 caliber machine guns, with armor shields, went onto either side of the cargo hatch. The modified M113 was now an armored cavalry assault vehicle (ACAV).