From Wiki:
Military service
At the beginning of the Second World War, Doohan joined the Royal Canadian Artillery and was a member of the 14th (Midland) Field Battery, 2nd Canadian Infantry Division.[10] He was commissioned a lieutenant in the 14th Field Artillery Regiment of the 3rd Canadian Infantry Division. He was sent to England in 1940 for training. He first saw combat landing at Juno Beach on D-Day. Shooting two snipers, Doohan led his men to higher ground through a field of anti-tank mines, where they took defensive positions for the night. Crossing between command posts at 11:30 that night, Doohan was hit by six rounds fired from a Bren Gun by a nervous Canadian sentry:[2] four in his leg, one in the chest, and one through his right middle finger. The bullet to his chest was stopped by a silver cigarette case given to him by his brother.[7] His right middle finger had to be amputated, something he would conceal on-screen during most of his career as an actor.[11]
Doohan graduated from Air Observation Pilot Course 40 with eleven other Canadian artillery officers[12] and flew Taylorcraft Auster Mark V aircraft for 666 (AOP) Squadron, RCAF as a Royal Canadian Artillery officer in support of 1st Army Group Royal Artillery. All three Canadian (AOP) RCAF squadrons were manned by artillery officer-pilots and accompanied by non-commissioned RCA and RCAF personnel serving as observers.[13][14]
Although he was never actually a member of the Royal Canadian Air Force, Doohan was once labelled the “craziest pilot in the Canadian Air Force”. In the late spring of 1945, on Salisbury Plain north of RAF Andover, he slalomed a plane between telegraph poles “to prove it could be done”—earning himself a serious reprimand. (Various accounts cite the plane as a Hurricane or a jet trainer; however, it was a Mark IV Auster.)[15][16]
Can anyone imagine a guy like this getting a job in Hollywood now?
The [Bren gun 7.62 x 51 mm] bullet to his chest was stopped by a silver cigarette case given to him by his brother.
Nah..! Not even three or four such cases stacked up would do that.
But kudos to him, all the same.