There was a bridge and American troops were moving over it. A German waited until a lot of troops were on it and blew the bridge. He was caught. Patton witnessed the incident and remarked that they should have shot him.
There was a patrol which encountered some German youths. The patrol lost some good men. The battle ended and the American officer in charge had his men tie up the the Commander of the German teenagers, and he clubbed him to death with his rifle.
In another incident, a sniper had killed some men of a unit. The sniper was captured alive, and a PFC dutifully began to take the sniper to the rear as a prisoner. The Lt who had lost men to the sniper yelled at the PFC and made him stop. The Lt took out his pistol and shot the sniper in the back of the head.
With the deaths of so many Americans our people weren't too hesitant at times to do what needed to be done.
The reason we have the Geneva Convention is so that we wind up with less deaths. Japanese did not follow the Convention, and so they tortured US POWs and killed many. Of course, the Japanese suspected that would happen to them so due to this, and to the dishonor of surrender, they would fight to the death and take many US soldiers with them.
My dad was in WW2 and I think he would agree that killing a POW is terribly wrong and those who did it shuld have been prosecuted. It is insurance that our POWs will be afforded better care and that the enemy will more likely surrender — as well as being the right thing to do.