In 1938 the US Army requested a more compact shoulder arm to replace handguns for their non-combat troops behind the line. Effectively the goal was to have a weapon that would be easier to train soldiers to fire accurately than the M1911, while still shooting a medium-calibre round. Unfortunately, however, the round that was developed for the M1 Carbine was a round-nosed bullet that limited it's effectiveness to approximately 200 metres, and severely limited it's lethality, despite having twice the muzzle velocity as a 0.45 ACP round that was used by the M1911. At an extended range the M1 Carbine was sometimes unable to penetrate even thick winter uniforms. That said, due to it's size, the M1 Carbine worked excellent in jungle conditions, and because it could be fitted with large-capacity detachable magazines it was capable of a high rate of fire.
M1 Carbine on Wikipedia