Inspired by dark thoughts.
It's 1945. Japan never attacked Pearl Harbor, so America never entered the war, although truly prodigious quantities of aid were sent to Britain (and Russia). Stalin, unwilling to bleed Russia white for the west, cut a deal in 1944 with the government of Reich chancellor Goering restoring the 1914 Russo-German border, which is as militarized as you'd expect.
In August, America detonates an atomic bomb in New Mexico.
So, there's Germany, Russia, Britain, and Japan.
What's the order for the bomb? My guess would be Britain, Russia, Germany, and then Japan (assuming that the other powers don't annihilate Europe), but I'm curious.