In the 1942 Pacific War theater of World War II, Lieutenant Sam Lawson, USN, is a Japanese-language interpreter who — so far — has avoided combat. His commanding officer, Captain John G. Nolan, unexpectedly cancels his leave and informs Lawson that he is to be assigned to a British infantry commando unit in the New Hebrides Islands for a combat mission.
The British base is in the middle of a large open field, several hundred yards from the edge of the jungle; on the other side of the jungle is a Japanese observation and communications post. Shortly after Lawson’s arrival at the base, a patrol of British soldiers sprint out of the jungle and across the open field, pursued by the Japanese. The base commander, Col. Thompson, instructs his men to keep well back, out of enemy range; they watch as the patrol are cut down by Japanese rifle fire.
Lawson’s commando group is instructed to destroy the Japanese radio transmitter to prevent them from sounding the alarm about an American naval convoy which is scheduled to appear on the horizon in three days. The post’s radio operator transmits an “all’s well” signal every night at midnight; it will be Lawson’s job to transmit a fake signal (in Japanese) to buy the Allies another 24 hours.
The commando group is led by Captain Hornsby, an upper class officer with a history of foolhardiness. The other members of the squad are draftees from Singapore whose enthusiasm for fighting leaves something to be desired: Pvt. Tosh Hearne, a cynical Cockney who is also the squad’s medic; Pvt. Jock Thornton, a lean Scot whom Lawson at first considers slightly cracked for skipping on patrol and singing the “Teddy Bears’ Picnic”, Pvt. Campbell, a fat Glaswegian; grey-haired Sergeant Johnstone; Signalman Scott the radio operator; Pvt. Griffiths, Pvt. Rogers, Pvt. Currie, Pvt. Connolly, Cpl. McLean, and Pvt. Riddle.
By the time the squad reaches the Japanese post, Riddle, Connolly, and Currie are dead from a botched ambush — which, Hearne mutters to Lawson, was entirely due to Hornsby’s incompetence: they were positioned on both sides of the trail, and the dead men seem to have been the victims of friendly fire. When Johnstone is wounded in another encounter, Hornsby leaves him behind; shortly thereafter, Johnstone is discovered by the Japanese and his throat slit.
After Scott drops and breaks the radio Lawson was to use, Hornsby decides to use the Japanese radio. Lawson flatly refuses to take part in any such scheme, giving the excuse that Hornsby is disobeying their orders with this extemporization. Nevertheless, Hornsby walks boldly into the Japanese camp and enters the radio hut without being spotted; he knocks out the radio operator and motions to Lawson and Scott. Scott goes to the hut, but despite Hearne’s urgings, Lawson refuses to go. The Japanese radio operator comes to, and in the ensuing fracas, both Scott and Hornsby are killed.
Lawson is now the ranking officer, with only Hearne, Campbell, Jock, Griffiths, and McLean left alive — and Jock has been wounded in the debacle. Japanese Major Yamaguchi (Takakura) is determined to stop them from reporting the existence of the secret Japanese airfield and planes they have discovered. Through loudspeakers in the trees, Yamaguchi exhorts the men to give themselves up. Lawson and Hearne agree that Yamaguchi is not to be trusted, but Campbell is in favour of surrender, and he works at Griffiths as Jock weakens. Finally, while Lawson and Hearne are asleep, Campbell tries to sneak off into the jungle; but Jock spots him and asks where he’s going. Campbell strangles Jock, wakes Griffiths and McLean, and the three of them run off.
Yamaguchi attempts to use the lives of Griffiths and McLean as bargaining chips. (Campbell, on the other hand, is killed in gruesome fashion after the Japanese discover he has a ring severed from the finger of one of the officers the patrol ambushed.) As Lawson and Hearne reach the edge of the open field adjacent to the British base, Yamaguchi announces that they have three minutes to surrender; Japanese soldiers have the field covered with rifles and machine guns. Hearne suggests that they give Yamaguchi a taste of his own medicine. They double back and shoot him. They then sprint out across the field. Despite cover fire from the base, first one, then the other is hit.
One of them rises and staggers to safety. It is Hearne. When Colonel Thompson asks who the other man was, Hearne replies, “A hero. He killed fifteen Japs single-handed — thirty, if you like.”