It was called the Tripartite pact. Perhaps the only time Hitler abided by a treaty
“If Hitler hadn’t been so crazy, it would not have. Germany had no treaty or agreement with Japan to fight anyone just because Japan did. Hitler declared war because he was a fool.”
You think we wouldn’t have fought the Hun had they not declared war on us? You think we’d have let Britain perish and focused on the Japs? There was no Japanese war. There was one war: THE WAR. Step in one part of it, you’re in it all. Germany’s declaration was merely a legal technicality anyway. With or without their little statement they posed zero threat to us, outside of U-boats in shipping lanes. Yet no one besides Pat Buchanon wastes much time on that distinction, just like no one would have cared at the time.
Simply put, Germany declared war not because it was crazy but because the U.S. was now in THE WAR, and the U.S. invaded Germany because Germany was in THE WAR. Their declaration was only useful in the U.S. for whoever cares about just war theory and pretends the meaningless is meaningful.
Except for the Tripartite Pact and, IIRC, there was an earlier one too.
This message was known to FDR (and Churchill) days prior to the attack. FDR mentions it the the US Congressional leaders the evening of 7Dec41 as they meet at the White House.