Comment by Quarrelsome

I don't mind the rationale for WW2 so much, I think the idea that Britain "didn't have to", doesn't scan. What the Third Reich was doing meant it would always be an existential threat that would ultimately result in conflict. So it was better for Britain to fight the Nazis than stay neutral.

I would however suggest that the two wars are basically the same war with just a big ceasefire in the middle, that's why I would treat them as the same mistake.