One of the ideals of Star Trek
is loyalty and courage in the face of great adversity. James Doohan lived this ethic in real life; Wikipedia
tells the story:
At the outbreak of World War II, aged 19, Jimmy Doohan joined the Royal Canadian Artillery, and was eventually commissioned as a lieutenant. His first combat assignment was the invasion of Normandy at Juno Beach on D-Day. Shooting two snipers along the way, Doohan led his unit made its way to higher ground through a field of tank mines and took defensive positions for the night. Crossing between command posts at 11:30 that night, Doohan took six hits from a German machine gun: four in his leg, one in the chest, and one through his middle right finger. The chest bullet was stopped by his silver cigarette case; the shot finger was amputated, and on screen he would generally conceal this. Despite his wounds, Doohan remained in the military, trained as a pilot for the Royal Canadian Air Force, and flew an artillery observation plane, though he was once labeled the "craziest pilot in the Canadian Air Forces".
See his IMDb listing and his Startrek.com bio, and this high-resolution image of Doohan posing with the plaque commemorating his star on the Hollywood Walk of Fame.