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.
Sorry. War sucks. Always has. We can't change that.
/johnny
Regarding the Germans, for the most part our people honored the Geneva Convention and took prisoners. There were some cases where a POW was shot. I won't defend nor criticize those decisions, but I do agree with your dad.
Max Hastings made a very interesting observation in one of his books on WWII in Europe. At some point, the German Generals knew that the war was lost. They could have saved the lives of hundred of thousands of soldiers and civilians. They could have surrendered, and they knew that the Americans would be merciful. But they didn't. Another irony is that the German soldiers fought on despite the odds. But for what were they fighting? The Allies were there to liberate the German people and their soldiers. The German soldiers fought on to keep a horrific system of Government in power, and in so doing, cost them their own lives and the lives of their loved ones.