TIL: Today I Learned...

The Russians did not declare war on Japan until something like 3 days before Hiroshima.

Italy and Japan both fought with the Allies in WWI, which led to Italian reluctance to fight against the Allies in WWII. Italy held down a 450,000 man Austro-Hungarian army on its northern border which prevented them from joining the Germans on the western front.
Another tidbit…Germany formally declared war on only one country in WWII, the US.