Answer:
1937
Step-by-step explanation:
When did WW2 begin? For the USA, it began in December 1941, although the US had been fighting the “Battle of the Atlantic” without Congressional approval for several months before that; for the USSR it is began in June 1941, although it had had a brief “winter war” with Finland in late 1939–40 and a brief skirmish with Japan in August 1939 (which is what made the Japanese army top brass decide that a naval attack on the US would be a easier proposition than any new involvement with Russia). For China and Japan it began in August 1937, and continued till August 1945, with more Chinese civilian deaths in Nanking/Nanjing in the atrocious sack of that city in 1937 than died in the U:S: atomic attacks on Japanese civilians in 1945. For Spain it began in June 1936, when Germany and Italy, aided by the covert “non-interventionist” help of the UK and France fought a proxy war with the USSR, but that war ended with a German victory, with Spain so exhuasted its Fascist government opted out of any military involvement in the fighting after 1939, although giving Germany all help (including sending “volunteers” to the Eastern Front).