Egotistical, hard-working Wedge Donovan, the owner of a highly reputed construction company, greets members of his crew as they return from a job for the Navy. Wedge is infuriated to learn that the men, who were working on a South Pacific island, were targeted by Japanese forces because technicians are irreplaceable. As civilians, the workers could not be armed and sustained heavy losses. Wedge lambasts Lt. Cmdr. Bob Yarrow, who was in charge of the mission, but is surprised when Bob agrees that the situation must be corrected. Bob invites Wedge to accompany him to Washington, D.C. and approach Capt. Joyce about establishing a construction battalion. In Washington, Wedge is enthusiastic until he learns that it will take months of military training before his men can be armed. Fed up with what he perceives as Navy red tape, Wedge says that his men will fend for themselves and storms out. Wedge then accompanies his crew to another small island in the South Pacific, where they are to build an air field. Also along is a group of war correspondents, including Constance Chesley, who is strongly attracted to Wedge, despite her romantic attachment to Bob. Wedge fights his own feeling for Connie, telling her to "stick with the guy who brought her." Wedge continually balks at Bob's strict Navy methods, so Connie tries to win him over with kindness, and the construction work progresses rapidly. One afternoon, however, an air raid siren sounds, and three of Wedge's men are shot by Japanese airplanes as they stand outside the bomb shelter. Believing that the Navy men have left them to be mowed down, Wedge and his crew grab guns and rush out to join the battle. They blunder into a trap that Bob and the soldiers have laid for the approaching Japanese forces, however, and the ensuing battle takes a heavy toll on the men, although the Navy eventually repels the invaders. Connie is shot by a wounded Japanese soldier as she runs on the beach, and before she passes out, she and Wedge declare their love for each other. Having heard the exchange, Bob questions Wedge, who asserts that he spoke only to comfort the wounded Connie. Wedge then attends to his injured men and can offer no resistance when Bob blames him for the damage. Bob still wants Wedge to help him press for the armed construction battalions though, and the reformed Wedge accepts a Navy commission and works alongside Bob. Later, after the workers have enlisted in the Navy and undergone rigorous military training, four platoons of the new Construction Battalions, nicknamed the Seabees, stand ready for duty. On the night before Bob and Wedge are to ship out, Connie returns to Washington, and Wedge tells her that she should stick with Bob. Although she is crushed by the rejection, Connie responds warmly when Bob confesses that he still loves her. Later, the Seabees return to the South Pacific, where they are to build a crucial oil depot. The work moves swiftly despite interference from Japanese snipers, and soon construction is complete. Eddie Powers, Wedge's foreman, is shot and killed as he opens the first oil valve, however, and an infuriated Wedge orders his men into the jungle to search for snipers. Bob receives a report of encroaching fog and, afraid that Japanese surface craft will slip in, goes to warn Wedge. While Bob is discovering that Wedge has abandoned his post to go into the jungle, a battle begins nearby. Airplanes from closely positioned U.S. battleships land for refueling, while anti-aircraft guns fight incoming Japanese planes. Japanese troops move onto the island, and Bob is wounded during a fierce gun battle. Wedge returns and reports to Bob, who wearily tells him that he will probably be court-martialed upon their return home. Bob then orders Wedge to protect the oil tanks at any cost, and Wedge's men spring into action. With the Japanese forces split into two columns, Wedge is forced to send his men after one side, while he attaches a bomb to a bulldozer and heads for the oil fields, where he intends to ignite one tank and spill the flaming oil onto the other enemy column. Wedge is mortally wounded but carries out his mission, and soon the enemy soldiers are routed. Later, back in the United States, Connie watches with pride as Bob announces to the assembled men that the President has issued a citation to commend the Seabees' courage under fire. Bob and Connie then embrace, and although Connie admits that the brave Wedge held a special place in her heart, she says that she has always loved Bob the most.