<Tr> <Th_colspan="2"> World War II </Th> </Tr> <Tr> <Td_colspan="2"> (clockwise from top left) <Ul> <Li> Chinese forces in the Battle of Wanjialing </Li> <Li> Australian 25 - pounder guns during the First Battle of El Alamein </Li> <Li> German Stuka dive bombers on the Eastern Front in December 1943 </Li> <Li> American naval force in the Lingayen Gulf </Li> <Li> Wilhelm Keitel signing the German Instrument of Surrender </Li> <Li> Soviet troops in the Battle of Stalingrad </Li> </Ul> </Td> </Tr> <Ul> <Li> Chinese forces in the Battle of Wanjialing </Li> <Li> Australian 25 - pounder guns during the First Battle of El Alamein </Li> <Li> German Stuka dive bombers on the Eastern Front in December 1943 </Li> <Li> American naval force in the Lingayen Gulf </Li> <Li> Wilhelm Keitel signing the German Instrument of Surrender </Li> <Li> Soviet troops in the Battle of Stalingrad </Li> </Ul> <Li> Chinese forces in the Battle of Wanjialing </Li>

When did world war 2 start and why