On December 11, 1941 Germany’s chancellor, the Nazi leader Adolf Hitler, declared war on the United States. His declaration of war against the U.S. came four days after the Japanese attack on Pearl Harbor. That’s what really happened.

Here’s my what-if—what if Hitler hadn’t declared war on America? What if, say, he had waited a year, in late 1942, before formally declaring war on the U.S.? What if an entire year passed, with the United States fighting Japan only? What might have happened?

I think the outcome would have been the geo-political equivalent of a new ice age, a vast overwhelming reconfiguration of the historical landscape. Like the ice age, we would clearly see the effects today. That’s because the key historical point was most Americans, while sympathetic to the British, were not at all inclined to formally join the Brits as an active wartime ally.

So, if Hitler holds off on his war declaration against the United States, there would have been no American declaration against Germany, no formal involvement with Great Britain. Sure, military aid would still have flowed, but not anything else. All American military manpower would have been devoted to fighting the Japanese. Without the ramped-up American military support, it’s very likely Great Britain would have been overrun by the Germans.

A British government-in-exile would have formed, perhaps in either Canada or Australia. I’m not sure Winston Churchill would have survived the German invasion; he might have insisted on staying behind to lead the last remnants of the resistance. In that case, Churchill’s death would have been quite probable. The impact of Churchill’s death would have deprived U.S. President Franklin Roosevelt of a key international, political, and personal ally.

A significant part of British society would have joined with the Nazis. The dynamics of responding to German control of Britain would have been greatly complicated and confusing. A permanent split would have opened up in British life, a split between those opponents of Nazism in exile and those supporters who stayed behind in England and the British Isles and joined with the Nazis. The scene would have resembled what actually occurred in Yugoslavia.

With the Germans in control of the British Isles, everything changes. Any Allied invasion of Europe would have either gone via Greenland-Iceland to the northern tip of Europe, or maybe from South America across the narrower portion of the Atlantic to western Africa. Moreover, the Allies would have placed much greater emphasis on local guerrilla resistance movements, including in England, Scotland, and Wales.

The Germans would have established concentration camps across either the northern European continent or somewhere in the British Isles.

India would have assumed a larger role in the global theater. American involvement with internal Chinese affairs would have intensified exponentially. This intensification would have profoundly affected the rise of Communism in China.

Air power, especially bombing, would have taken on a wholly different meaning. The atomic bomb would have been used in Europe and Asia alike.

Taken together, the world war’s orientation and critical mass would have shifted for Americans to Africa and China.

Back within the United States, the congressional election of 1942 becomes the most significant “off-year” election in the American Experience. Swirling around the election are such issues as the exiled British government, the conduct of the British people in occupation, and the success of guerrilla-oriented resistance movements, all of which would be weighed against strong American public support for a “Japan-first, Japan-most” focus of war-fighting.

If Hitler decides not to declare war on the U.S. and instead waits another year before doing so, everything changes.

What do you think?