There is also the commonly quoted WWII statistic that only 30% of soldiers in combat actually fired their weapon, and only around 2% actually aimed at a specific enemy soldier with the intent of killing him. That is why the US army invested heavily in first-person shooter computer games, the series of America’s Army games is distributed by free download from 2002 till present.
The live-fire rate of american soldiers in combat is now over 90%, as the games get you used to targeting enemies, and recovering instantly if you yourself are hit. Some would say this is programming game-players to have the emotional responses of a psychopath. It is hard to imagine the WWI Christmas Truce occurring today.