Pretty widely known. As mentioned by someone else, Victor Davis Hanson has some good stuff on the subject. And again, Tooze discusses it some in his book, though it mainly focuses on economic matters—but Hitler would be the first to tell you that he was waging an economic war. He considered his military as a means to improve the German economy—through war and conquest, thus his alliances had economic reasoning as well. Getting the Japanese on his side woud be a big bonus to him, since they had a big fleet and he didn’t, and the excellent Italian navy was confined to the Med and could barely sorty due to lack of oil anyway.
The Germans were caught by surprise by Pearl Harbor and their declaration of war basically only codified what was already a reality in the Atlantic. Our destroyers were already escorting convoys and chasing subs. The Willow Run plant was in full operation 6 months before the war and sending Liberators to Britain.
Six months before Pearl Harbor when the Bismarck was sunk, she was located by a US Navy PBY crew with a sheep dipped RAF man aboard.
Hitler’s declaration was merely a recognition that the war was already underway.
Thanks for that.