"If the war of 1870 dealt a blow to the First International, disclosing that there was as yet no fused mass force behind its social-revolutionary program, then the war of 1914 killed the Second International, disclosing that the mightiest organizations of the working masses were dominated by parties which had become transformed into auxiliary organs of the bourgeois state!"
1943 was the end of III International. It was the Second World War that finished that corpse.
1) Franco-Prussian war brings to end I International
2) WWI brings to end the II International, while creating pre-conditons for the next one.
3) WWII brings to end the III International. IV International was born in anticipation of that war.
Major, world wars seem crucial to ending "old" international organizations, and creating grounds for the next one.