James Doohan’s Montgomery Scott wasn’t often the centerpiece of “Star Trek” storylines, but he could always be counted on to save the day by eking some kind of miracle out of the Enterprise’s transporters or warp engines. Doohan’s performance was lively, and “Scotty” lovable and charismatic, even if the Canadian actor’s for-television accent was once included on the BBC’s list of “Film Crimes Against the Scottish Accent.” According to The Guardian, Doohan based the voice on that of a Scottish soldier he met in World War II.
Indeed, Doohan was a soldier before he had any interest in acting. He joined the Canadian artillery after high school, right as the largest conflict in human history was brewing. He rose to the rank of lieutenant and was sent to Britain to prepare for Operation Overlord, the invasion of Normandy (Valour Canada). Long before Scotty saved Kirk, Spock, and his other comrades from all sorts of alien enemies and celestial phenomena, he led men into the fires of D-Day, June 6, 1944.
Following a naval and aerial bombardment, Canadian units stormed Juno Beach. James Doohan and his men unknowingly ran across an anti-tank minefield, being too light to detonate the defenses (Snopes). Bullets piercing all around, they reached cover and advanced inland. Doohan made his first two kills of the war by silencing German snipers in a church tower in Graye Sur Mer.
After securing their positions, Doohan and his troops rested that evening. But just before midnight, everything went wrong for our future chief engineer. Stepping away from the command post for a smoke, on his way back his body was riddled with at least half a dozen bullets. The middle finger of his right hand was torn off, four bullets hit his knee, and one hit his chest, but did minimal injury because it happened to strike the silver cigarette case in his breast pocket. But this was no German attack. It was friendly fire.
According to Valour Canada, James Doohan was shot by a Canadian sentry who mistook him in the night for a German soldier. This sentry has been described as “nervous” and “trigger-happy” (Snopes). Doohan later said that his body had so much adrenaline pumping through it after the shooting that he walked to the medical post without even realizing his knee had been hit.
Doohan survived the incident and the war, moved to the United States, and started acting in 1950 (IMDb). Sixteen years later, after small roles in “Gunsmoke,” “The Twilight Zone,” “The Man from U.N.C.L.E.,” and more, he landed the part that would bring him global fame. According to StarTrek.com, Doohan had a hand double to conceal the missing finger while filming close-ups on “Star Trek.” However, it is still obvious in many shots, stills of which fans have collected, for instance on this Stack Exchange.