The 503rd Parachute Infantry Regiment was an independent paratrooper regiment during World War Two that fought in the Pacific Theatre. The units' most famous action was the Battle of Corregidor, where the regiment was dropped onto Corregidor Island off the Philippine island of Luzon, which had been turned into a fortress by the Americans before the war and occupied by the Japanese.

Faced with the prospect of deep tunnels and pillboxes, the paratroopers resorted to using cans of gasoline as ersatz flamethrowers into ventilation shafts, or attaching explosives to them to make fuel-air bombs to collapse cave entrances. Conventional reinforcements brought actual flamethrowers to the battle, allowing the Americans to make further inroads and capture the fortress.