On that day American, Canadian, Polish, British Empire, and other Allies stormed the beaches to free Europe from the two extremes of Nazism and Communism. Yes, that was an example of a just war, even if unjust things were done pursuing it.
I fear that these days the liberation of Europe is used too often to justify American expansionism, or to fire up jingoism. In fact, veterans are already angry at Bush for trying to compare Iraq to WW2.