The victorious Allied powers occupied Japan after WWII. The occupation was leaded by General Douglas, from the US. The main difference, if compared to the occupation of Germany that the Allies conducted too after WWII, is that the Soviet Union barely participated this time.
A parliamentary democracy was created to replace the Empire, and its economy was leaded according to the principles included in President's Roosevelt New Deal.
The occupation ended in 1952, and Japan recovered its full sovereignty.