My Dad was in the reserves when the war broke out. They reassigned them from Artillery to Tank Destroyers. The fist time the encountered a Tiger Tank (they had 13 tanks and the Tiger was looking the wrong way) their shells bounced off it like ping pong balls. The Tiger blew away 9 of the 13 tanks, and the rest ran. My Dad was one of only 2 in the original unit that returned, all the rest were replacements. He was in Battle of the hedge rows and battle of the bulge.
My FIL was a navigator on a B-24 and flew over 30 missions. He used to tell the story of the new guy who lied about his age (was only 17), got so scared when the flack started exploding that he peed his pants, and it froze and he was stuck to the seat.
Neither one talked much about it, and they are both gone now.
I know my Dad said when a German Jet flew over their heads it scarred the crap out of them, because they knew we had nothing like it. Luckily, we were able to bomb the factories when Hitler started to build them, or .....
It must have been very difficult being out there for years, not knowing if you would prevail. My Dad told my mother he never expected to come home, thought it was a matter of when, not if.