The film traces the progress of three Marines on shore leave during World War II, in the Pacific. One of the men, Nico, is a seasoned, decorated sergeant; the second, Frankie, is a perennial goof-off, who drinks too much; and the third, Alan, is an intellectual from a wealthy family. He has joined the Marines, despite his father's protests. Nico, Frankie and Alan come to San Francisco on a furlough from the war. Nico proposes and marries his pregnant girlfriend Andrea. A drunken Frankie fights with Charlie Stanton, his hateful stepfather, who thinks him a coward. The wealthy Alan catches his fiancée, Sue, with another man. Lorraine, who is in love with Frankie, has joined the military as a WAVE. She introduces his friend Alan to her roommate Kalai, a nurse of Hawaiian-French heritage. They all go to Lorraine's apartment, where Frankie first passes out, then wakes up screaming at the thought of returning to the war. Lorraine decides to leave him. Kalai professes her love for Alan. The three men return to the Pacific front. Frankie initially shows cowardice and Nico slaps some sense into him. Later, Frankie saves Alan and is honored for his heroism. Alan becomes ill with malaria and when a wounded Japanese soldier calls out to him for help, he tries to give the Japanese soldier some water but Nico shoots the wounded soldier and reveals to Alan and the other marines that a grenade was hidden under the wounded soldier as a trap. Alan then begins to question the futility of the war. When an advancing enemy tank threatens the platoon, Nico singlehandedly blows up the tank, but dies from his wounds. Back home, Kalai visits Sue in the hospital after she tries to commit suicide. Suffering from alcohol withdrawal, Sue dies during Kali's visit. The war ends and Alan returns to Kalai and becomes a professor at the local university. Frankie, now promoted to sergeant, brings Nico's last love letter home to Andrea, who has given birth to their child. Andrea tells Frankie that she would like to see him again.
Jerry Wald, who had a deal with Fox, bought the screen rights to The Big War in March 1957. It was one of a number of war novels bought by Fox at the time, including The Young Lions, The Hunters and The Enemy Below. At one stage the film was known as Hell Raisers before being titled In Love and War. Wald wanted Lee Remick, Richard Widmark and Ben Gazzara to play the leads. Bradford Dillman and Robert Wagner were cast in April 1958. Jeff Hunter and France Nuyen were cast in June. Filming started in June 1958. Dunne says filming started with "half a script" and he had to do writing onlocation in the Pacific.
