My father was watching the WW II Memorial on t.v. He was moved to tears, thinking back on those years. He was at Omaha Beach a few months after D-Day. He was around when two concentration camps were liberated and he said that if he had realized how he was going to feel, he would have arranged to go to D.C.
"Good and evil were really clear back then," he said. "We went. We did a job. And we came back and went to work building this society."
Good and evil were clearly defined, because in some part, the tactics were also clearly defined. Either side could do as much as it could, and use whatever weapons it had - to destroy the other side. In other words, WWII was something of an old-fashioned war.
All wars since then - not clearly defined. Reason: The A-Bomb. When WWII ended with the introduction of the nuclear age - it changed the ethos of war. It was no longer plausable to just use all your weapons to destroy the other side. Things turned gray.
Now there is no doubt that the United States can destroy its enemies many times over. What is paradoxical, is that the enemy is still fighting that old type of war - let's destroy and disrupt the enemy by killing as many citizens or soldiers as we can.
In other words - getting back to WWII - it ain't so clear cut. The rules of WWIII are that the enemy, since they are at a tactical disadvantage, feel allowed to target civilians - as many as they can get - in any way they can do it.
We, on the other hand, will kill civilians - but generally by mistake - or as part of some kind of calculation. And for sure we don't use all our power because then we would be seen as simple conquerers.