This depends on your point of view. Hitler attacked countries before the start of WW2 and attacked Poland even though he had been told by Britain and France they would go to war if this happened. From here during the 'phoney war' there were only minor scuffles until the invasion of Belgium and France.
Tokyo
Poland
they blew the pilots
the Zimmermann note
This was Americas (and the worlds) first major war of the atomic age. It taught the US (and the world) how to fight a limited war (limited to conventional weapons...no nukes).
No. Early on, the allies agreed to go after Germany first.
Mexico
1939
Poland.
Poland
Americas first battle was at pearl harbour in Hawaii.
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Poland
Poland attack by Nazi.China Attack by Imperial Japanese Army.Ethiopia attack by Italy
The first attack which was at the start of the war was when Nazi Germany and the Soviet Union invaded Poland. World War 2 began in 1939. This caused the war after a couple of years of building up tension between the allies and the Nazis.
Bangladesh
Poland in September of 1939.