I can't speak for Japan, a total lack of experience in that department, but Germany is still licking some of its wounds 55 years later.

Don't forget that East and West Germany got reunited in fairly recent times and the shockwaves of the reunion have not yet subsided.

Actions have consequences. Could Germany be even more prosperous if it hadn’t started a war? Possible. But if that’s what they wanted then they shouldn’t have started a war with the explicit goal of, well, world domination.

Germans today are just as rich as the French or Britains, much richer than Poles or Russians. Germany has the fourth largest economy in the world (behind China, Japan and the US). The world owes us nothing, we owe the world.