Ol’Fat Boy should know that the concept of a fair fight during war died about 1862.The enemy is to be killed whenever the opportunity presents itself.
A lot earlier than 1862. The Brits were appalled at the way colonial militia used sharphooters to directly target officers and scouts.
Conventional rules of war at the time dictated that officers be captured alive and be treated well. Washington and the continental army were holding to those rules but the militia was doing what worked.
In those days your average infantry soldier tended to be a pure follower and the elimination of an officer tended to put troops into disarray.
As a young British Officer Washington himself got into trouble over the killing of a captive French officer.