[ianremsen]

In my opinion, World War II started on September 18, 1931, when Japan invaded Manchuria, because 1) the Chinese and Japanese didn't stop fighting until 1945, and 2) it had much the same spirit as the following conflicts. Admittedly, this subjective timing stuff is awful fuzzy.

[ptaipale]

I agree with this idea; the view that invasion of Poland was start of this global war is rather Euro-centric.

However, as you said it is fuzzy: the hostilities were still somewhat limited even after the invasion in Manchuria; but total war broke out in July 1937 after the Marco Polo Bridge incident.

[vacri]

Japan's invasion of Manchuria triggered which web of military alliances to fight against which web of military alliances?