In 1947, Steve McQueen joined the United States and was promoted to Private First Class and assigned to an armored unit. Initially, he reverted to his prior rebelliousness, and was demoted to private seven times. He took an unauthorized absence by failing to return after a weekend pass expired, staying with a girlfriend for two weeks until the Shore patrol caught him. He resisted arrest and spent 41 days in the brig. After this, McQueen resolved to focus his energies on self-improvement and embraced the Marines' discipline . He saved the lives of five other Marines during an Arctic exercise, pulling them from a tank before it broke through ice into the sea. He was assigned to the honor guard, responsible for guarding then US president Harry Truman's yacht. McQueen served until 1950 when he was honorably discharged. He later said he had enjoyed his time in the Marines.
Here's some great fotos of him that I think haven't been posted yet, it's on another Military related site, so we'll just link it to view them rather than copy them here.