GOM
living vicariously
When did WW2 start though? 1937 or 1939?
The answer may well depend on where you live in the world. From a UK-centric view, then yes, of course, we are all taught 1939. But, as I understand, there are plenty of historians that would beg to differ, and with some reason. Japan's full scale invasion of China in 1937 was hardly a minor skirmish, even if we were not directly involved.
I am not an historian, and certainly no expert, so stand to be corrected. But there does seem to be a widely held view that, in Asia, WW2 started in 1937.
Quite simply, in potted fashion and not withstanding all the details, the war in Asia was not a world war, it was an Asian war. 2 years later when war was declared in Europe there was a European war. Once Japan attacked Pearl Harbour and USA officially became involved, the war became global (a world war) with alliances being formed and fighting between nations both in and outside of their own continents.
There are of course many more nuances to this but we don't have time to write a new reference book.