Who defines a moral war? In 1940 the USA believed that we had no part in the conflict (isolationists): it was just another European fratricidal event that we should stay out of.

The war didn't get a moral parameter until the Janaese attacked on Dec 7, 1941.

Even then, a large minority thought the war should be fought exclusively against Japan and let the Europeans deal with their own problem. It took an awful lot of masterful propaganda by Churchill and Roosevelt to change that. Was the persuasive propaganda moral?

It's always clearest in hindsight.