So turns out Sterling Hayden had a super interesting life. Most famous for playing General Jack D. Ripper in Kubrick's Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb (1964), he was a higly decorated soldier in WWII and was in the predecessor of the CIA for a short while, but the crazy thing is that he did all that under a fake identity!

Could someone just randomly make up a fake ID and join the military back in the 40s? Was it really that easy?

He returned to the US and tried to buy a half-interest in a schooner but could not raise the money. He joined the United States Marine Corps as a private, under the name John Hamilton, an alias he never used otherwise. While at Parris Island, he was recommended for Officer Candidate School.

After graduation from OCS, he was commissioned a second lieutenant and was transferred to service as an undercover agent with William J. "Wild Bill" Donovan's Office of the Coordinator of Information. He remained there after it became the Office of Strategic Services (OSS).[14][15][16]

As OSS agent John Hamilton, his World War II service included sailing with supplies from Italy to Yugoslav partisans and parachuting into fascist Croatia. Hayden, who also participated in the Naples–Foggia campaign and established air crew rescue teams in enemy-occupied territory, became a first lieutenant on September 13, 1944, and a captain on February 14, 1945.

He received the Silver Star for gallantry in action in the Balkans and Mediterranean (according to his citation, "Lt. Hamilton displayed great courage in making hazardous sea voyages in enemy-infested waters and reconnaissance through enemy-held areas"), a Bronze Arrowhead device for parachuting behind enemy lines, and a commendation from Yugoslavia's Josip Broz Tito. He left active duty on December 24, 1945.[16] Tito awarded him the Order of Merit.[17]