Bill V,
I agree that the war in Europe started in 1939, and that Japan was an ally of Nazi Germany. The USA remained neutral until December 7th, 1941, when Japan attacked multiple locations in the Pacific, starting with Pearl Harbor to cripple the US fleet so we could not come to the aid of the other Pacific island nations who were also attacked. FDR then declared War against Japan on December 8th, and Germany followed that by declaring War against the US.
Japan had actually declared war on the US at the time of the attack (December 8th in Japan, and December 7th in the USA) which was a day before FDR declared war on Japan.
The war in Europe ended first, but war with Japan continued until atomic bombs were dropped on Hiroshima and Nagasaki, eventually forcing the Japanese to surrender. The Japanese and Gen. McArthur signed the instruments of surrender aboard the USS Missouri anchored in Tokyo harbor.
We never count wars and hostilities between other nations as US wars until we get involved with combat troops. So the USS Arizona represents the start of WWII in the eyes of the US, and the USS Missouri represents the end of WWII.... Until the December 7th, 1941, it was just refered to as "The War in Europe", and the US was not involved or taking sides.
I'm sure Poland and the other countries all have different dates for WWII based on when their countries became involved and when the hostilities ended. I suspect that there are many Polish people who feel that they were never liberated until the fall of Communism in 1989?
...Rich