A movie career died aborning in 1941 when Stirling Hayden joined the Merchant Marine.  In 1942 he entered the Marines.  He's shown here at boot camp.
After the war his movie career was resurrected and he starred in many film noir films as well as a lot of westerns.

Actor Stirling Hayden - Marines

Tyrone Power enlisted in the Marines in 1942, won a commission and his wings as a pilot, was promoted to a first lieutenant. 

Actor Tyrone Power - Marines

British-born Louis Hayward (now a U.S. citizen) chose the non-glamorous job of combat photographer when he joined the Marines in 1941.  As a captain, he headed the crack combat film unit at Tarawa, where he won the Bronze Star.  This picture shows him after the fighting ended there.  In 1944 he was given an honorable discharge.