36 Hours of Hell (1969)

(aka)36 ore all'inferno. The story is explained in a lengthy introduction as a war correspondent narrates some really, really bad looking stock footage: In 1942, the Japanese dominate the Pacific. The American air force has been bombing one small island, which they now intend to occupy and use a base for launching the invasion of Rabaul. A Marine platoon led by Captain Stern (Richard Harrison, "Churchill's Leopards") has 36 hours to scout the island and make sure all of the Japanese resistance has been wiped out before the Allies launch one massive, final bombing mission.