Good actors can play courageous heroes -- sometimes because they have that spark of greatness within them. Here's a look at five science fiction actors who played imaginary heroes on screen, but were also real heroes on the battlefield.

James Doohan (1920-2005) played Montgomery “Scotty” Scott on Star Trek (1966-1969). Born in Vancouver, Canada, he joined the Canadian Army at the age of 19. He served in the Royal Canadian Artillery, rising to the rank of captain. Doohan was the first man off his landing craft on Juno Beach during the 1944 Allied invasion of Normandy. He was shot by a German machine-gunner six times, four rounds in one leg, one in the chest, and one in the hand. The bullet aimed at his chest was stopped by a metal cigarette case. Doohan lost the middle finger of his right hand -- a fact that the directors of Star Trek tried to hide from the cameras. When directors needed to show Scotty’s hands, a stand-in was used in Doohan’s place.

Don Matheson (1929- ) played Mark Wilson on Land of the Giants (1968-1970). He enlisted in the US Marine Corps at 16 and completed his high school education in that service. After ten boring months of civilian life, Matheson decided to become a paratrooper. He enlisted in the Army and completed twenty jumps before being transferred to the Criminal Investigation Division in Korea during the Korean War. He suffered abdominal wounds, either by an enemy mortar or grenade, and was awarded a Purple Heart and a Bronze Star. When he recovered, Matheson was tasked with investigating heroin trafficking among US forces in Korea. He was so successful that he was recalled stateside to brief senior officers on illicit drug use by American soldiers. Matheson’s skills later served him well as an undercover narcotics officer with the Detroit Police Department.

Patrick Troughton (1920-1987) played the Second Doctor (1966-1969) on Doctor Who (1963- ). He was on Long Island, New York when World War II broke out. His father arranged for him to return to Britain on a Belgian (then a neutral) ship. The ship hit a mine and sank, but Troughton escaped in a lifeboat until a Greek ship picked up survivors. He enlisted in the Royal Navy in 1940, was trained at Loch Ewin, and commissioned as an officer. Troughton participated in daring raids against German shipping off the Dutch coast. He later received his own command and guarded convoys and rescued downed airmen in the North Sea.

Rod Serling (1924-1975) was the producer and writer responsible for bringing The Twilight Zone (1959-1964) to television. In 1943, the day after he graduated from high school, Serling enlisted in the US Army. While still stateside, he became an accomplished Army boxer, but saw more dangerous combat when he was deployed to the Philippines as part of the 11th Airborne Division. During the liberation of that country, he was badly wounded by shrapnel and received the Purple Heart and the Bronze Star.

Serling was haunted by the war and suffered nightmares for the rest of his life. Much of his writing was in response to his wartime experiences, such as the third season episode "A Quality of Mercy", which takes place in the Philippines during the closing days of the war.

Alec Guinness (1914-2000) played Obi-Wan Kenobi in Star Wars. During World War II, he was an officer in the Royal Navy Reserve. He was trained on the HMS Raleigh, a “stone frigate” or naval base in 1941, and then at a similar establishment in Hampshire, before completing his training on Loch Fyne. After getting practical experience on the HMS Quebec, Guinness sailed to Boston in January 1943 to pick up his first command, a landing craft designated LCI(L) #124. He took his ship through strafing runs by German aircraft to North Africa, where he prepared for the Allied invasion of Sicily. On 9 July, he landed 200 men on Cape Passero.

Due to a communications breakdown, he did not receive a message that the landings had been delayed an hour, and consequently, his ship arrived at the Sicilian beach alone. Further miscommunication led a Royal Navy commander on the scene to accuse Sub-Lt. Guinness of not being early, but being late, and insinuated that the young officer’s acting career had not adequately prepared him for his military duties. Guinness responded:

And you will allow me to point out, sir, as an actor, that in the West End of London, if the curtain is advertised as going up at 8:00 PM, it goes up at 8:00 PM, and not an hour later, something that the Royal Navy might learn from.

Photos: Paramount Pictures, ABC, BBC, CBS, and Lucasfilm, respectively.