The Second World War usually seems to be be given a starting date of September 1939, when Britain declared war on Germany after the invasion of Poland, and an ending date of August 1945, when Japan surrendered after the bombings of Horishima and Nagasaki. My question is, why is this treated as one continuous war, rather than two separate conflicts happening on opposite sides of the world, which just happened to both involve the UK and the US.
I know that Germany and Japan had some sort of 'alliance', but what did this entail exactly? What did their imperialistic ambitions have in common apart from the fact that Britain had colonies in the far East and Australasia. It seems that the only thing Japan did for Germany was get America involved, which arguably was a significant factor in Germany's eventual defeat.
So...yeah, that's about it. I hope someone with more understanding of history and military strategy than I do can help me out. This is something that has always bugged me but I've been too afraid to ask for some reason.
Distance does not divide wars. If Britain fought France and Denmark who were allied with each other at the same time then it is one war. If Britain fought Germany and Japan who were allied with each other at the same time then it is one war. The British Empire was a global entity and it was fighting two enemies who were working together even if they were thousands of miles apart and din't actually go on any joint operations. Germany and Japan also fought Russia at more or less the same time.
Which is why I said "more or less at the same time" as it was a couple months after Germany got defeated.
The bottom line is if two parties say "Hey we're on the same side and we're both gonna fight your side" then regardless of whether they fight together or not they are still both fighting against you and it is one war.
Yes, I know Russia attacked Japan three months after the defeat of Germany, but what's important here is that was only because the war in Europe was over. While the Soviet Union was fighting Germany the war in the Pacific was a separate conflict they didn't need to get involved in.
As already stated, Germany and Japan were Allied, alongside with Italy. Hostilities that have to do with the whole conflict actually started in 1937 with the Japanese invasion of Nationalist China. Yet the Invasion of Poland is taken as a point where the conflict truly turned into a World War.