Answer: One
Corporal Upham only killed one German in the entire movie. Upham was the French and German translator for the squad, and had a certain sympathy for life, and disliked conflict, regardless of who was shooting and who was dying. That's why he vouched for the German P.O.W. back at the radar station. When Upham saw that same German, who was originally supposed to turn himself into the Americans had really gone back to his own side, to fight again, he was furious that he had taken advantage of Upham's good will. In his disgust, Upham killed the German, after he confirmed that it was the same soldier from the radar station. This particular German was the also the one who was responsible for killing Captain Miller, as he shot him last.