A generic term for a whole series of box-shaped military armored combat vehicles, starting off with the original M113 Armored Personnel Carrier
), capable of carrying 11 soldiers into battle under armored protection plus a driver and commander. More importantly, the M113 series can be easily transported by air, even airdropped and submerged.
The basic M113 design, actually nothing more than a box on treads, with a slanted front, has been used in many different roles and been modified to fit those roles. For instance, M113 variants have been used not only as a troop transports, but mobile mortars
, command vehicles, cargo carriers...
The basic M113 (first produced in 1960) was powered by a Chrysler V8 gasoline engine, reached speeds of up to 37 mph and pulled around 209 hp. It weighed 23520 pounds fully loaded.
The M113A1 came out in 1964. It was a modification of the original, swapping the old engine for a Detroit Diesel and enlarging the fuel tank from 302 to 360 liters. The new engine did not do much more than increase the acceleration somewhat.
The M113A2 was more or less a minor bugfix. Many small things like suspension and powertrain were tuned.
The M113A3 was released in 1987. Most improvements were interior, like the replacement of the tiller bars by a steering wheel and brake pedal, but the engine was also turbocharged and brought the M113 up to 41 mph at 275 hp.
The M113 is actively in use by over 50 countries, in more than 40 distinct variants.