Officially... from 7 December 1941 till their surrender in Tokyo Bay in August of 1945. But, we were supplying the Chinese with flights "over the hump" in 1940. We also helped cobble together the "Flying Tigers"...
Japan.
The US was in the World War 2 from December 7/8th 1941 to August of 1945. They had to stay in Europe and Japan for many years after the war too.
Axis is the term of Germany, Italy and Japan union in that war. Italy did not last long but the leader Benito named that term.
The Allied powers occupied Japan for nine years following the conclusion of World War Two. Troops left the island of Japan in 1954 leaving the Japanese government to rule themselves for the first time in over 10 years.
Iraq: Congress authorized it, which constitutes a declaration of war. The last formal declaration of war was against Japan in World War II.
6 years
'40-'45
3 minutes
WW2 ended when Japan surrendered because they were the last Axis power that continued to fight.
Japan bombed Pearl Harbor, Hawaii on December 7th in 1941 and World War 2 officially started for the United States. Japan had been fighting long before that though. Japan had been after the South Pacific and China for a long time before that. Many say they started the war in 1937.
They were officially in World War 2 6 years but they had started warring back in the 1930s.
Japan was defeated in World War II.