I think they were just beaten into submission wildwood. Japan was exhausted and shattered after 1945.
As I understand it, Japan was forced to open itself to western trade in about 1868 by the US Admiral Perry (?) and his Black Ships. From that point, the Japanese felt that if they were being forced to engage with the world, then they may as well adopt western values and ideas to further their own economic and military dominance. Hence their construction of the great Imperial Fleet that shattered Russia in 1905. From then, they formed the idea of the Great South East Asian Co-Prosperity Sphere which was basically a Japanese empire in the Pacific. After the Washington Naval Treaty of 1921, Japan built the great navy that attacked Pearl Harbour in 1941. They then grabbed vast territories in south east Asia to ensure supplies of raw materials. After Pearl Harbor, the US counter-attacked and pushed all the way to Japan culminating in the atom bombs and the destruction of Japan as a world or Pacific power. Japan was then occupied by the US (governed by MacArthur) and so battered they were forced to be a peaceful nation.
A bit brief but that's off the top of my head.