The Americanization of Emily (1964)

During the build-up to D-Day in 1944, the British found their island hosting many thousands of American soldiers who were "oversexed, overpaid, and over here". That's Charlie Madison exactly; he knows all the angles to make life as smooth and risk-free as possible for himself. But things become complicated when he falls for an English woman, and his commanding officer's nervous breakdown leads to Charlie being sent on a senseless and dangerous mission.