Good question. I hope we never have to learn that.

I recall an Army marksmanship study (not sure whether it was post Korea or post Vietnam, hell it may have been post WWII!), trust me on this .......

Anyway, they found that a large percent of American soldiers in combat never fired their weapon. Of those who did fire, few of them aimed.

So the army changed from circular, bull's-eye targets to silhouette targets and the percentage of soldiers shooting to kill increased. Nowadays we train as we fight. Our soldiers are far more lethal today than at any time in American history, regardless of weapon. Most will shoot to kill.

And this is why the special operations forces use live fire training. Not only must they shoot first and accurately, they must not shoot each other. Live rounds makes people take shyte seriously.