If your dad was in the 9th Inf. Div. 15th Engineer Bat. he may have served w/ my grandfather. Small chance I know, but stranger things happen....
While I'm tempted to go with the 1911, for semiauto I'd pick the Browning. 9mm may not pack the punch of the 45acp it's higher capacity and lower...
I think it could be a Czech made Mauser, a 98/22 or Vz24, 7.92x57mm. These rifles were used by the Germans and were also exported to many...
A semi-auto yes. At 100 yards the -average- solider would be extremely lucky to hit a human sized target in the middle of combat. On a target...
If not invading Russia isn't an option then: -Not invading Yugoslavia and Greece and pushing back the timetable of Barbarossa. -Winter...
Anywhere on the Eastern Front in a Soviet penal battalion.