<Table> <Tr> <Th> Timelines of World War II </Th> </Tr> <Tr> <Th> Chronological </Th> </Tr> <Tr> <Td> Prelude <Ul> <Li> (in Asia </Li> <Li> in Europe) </Li> </Ul> </Td> </Tr> <Tr> <Td> <Ul> <Li> 1939 </Li> <Li> 1940 </Li> <Li> 1941 </Li> <Li> 1942 </Li> <Li> 1943 </Li> <Li> 1944 </Li> <Li> 1945 onwards </Li> </Ul> </Td> </Tr> <Tr> <Th> By topic </Th> </Tr> <Tr> <Td> <Ul> <Li> Diplomacy </Li> <Li> Declarations of war </Li> <Li> <Ul> <Li> Engagements </Li> <Li> Operations </Li> </Ul> </Li> <Li> Battle of Europe air operations </Li> <Li> <Ul> <Li> Eastern Front </Li> <Li> Manhattan Project </Li> </Ul> </Li> <Li> United Kingdom home front </Li> <Li> Surrender of the Axis armies </Li> </Ul> </Td> </Tr> <Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> </Table> <Tr> <Th> Timelines of World War II </Th> </Tr> <Tr> <Th> Chronological </Th> </Tr> <Tr> <Td> Prelude <Ul> <Li> (in Asia </Li> <Li> in Europe) </Li> </Ul> </Td> </Tr>

The main reason the united states entered word war ii was