<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> The Second Sino - Japanese War was a military conflict fought primarily between the Republic of China and the Empire of Japan from July 7, 1937, to September 2, 1945 . It began with the Marco Polo Bridge Incident in 1937 in which a dispute between Japanese and Chinese troops escalated into a battle . </P> <P> During the Marco Polo Bridge Incident Japanese military demanded permission to enter the Chinese city of Wanping to search for a missing soldier . The Chinese refused . Later in the night, a unit of Japanese infantry attempted to breach Wanping's walled defences and were repulsed . An ultimatum by the Japanese was issued before they would declare war . The Chinese still refused . </P>

When did the second sino japanese war start