Eighty-four years ago, Germany invaded Russia.

[DFW]

1. The biggest, for sure

He thought that because he had been so successful (except for Great Britain--so far), that he could do better than Napoleon. Instead, just as with Napoleon, his attempt to invade and conquer Russia was his undoing. I hate to think of the slaughter that would have occurred if the Allies had been forced to face invading occupied France (or, worse, Britain!) facing a Wehrmacht completely unencumbered by a second war on the eastern front.