USS Clueless:

It took a direct order by Emperor Hirohito to make it happen. After Hiroshima and Nagasaki, he finally bestirred himself and ordered a surrender. And with that, the entire martial tradition shattered like broken glass. The influence of the samurai on Japan was destroyed forever, and Japan is now ruled by its merchants, as are the Western nations.

It took a crisis of faith; it required the people of Japan to believe that they were defeated. They had to give up a thousand years of cultural chauvinism, to accept deep within themselves that their culture was inferior in practice, and had to be replaced.