Hirohito is probably the individual most responsible for the transformation of Japan into what it is today.
He strove to become a leader in the image of his grandfather, Emperor Meiji, and he was surrounded by people who wanted him to be the leader that his father, Emperor Taisho, was incapable of being. He was educated to believe himself to be a god and incapable of any wrongdoing, and he sometimes ruled the country in an almost reckless manner. Hirohito was also presented in propaganda to be an emperor with an interest in the commoner and a regent who was in touch with the plight of the Japanese people, when in reality, he was hopelessly out of touch with society. He ruled indirectly through what appeared on the surface to be a real government, using the massive influence of the monarchy, and was possibly responsible, or at least aware and consenting of Japanese military activities in Asia during the first half of the 20th century, including the declaration of war on the United States. He also was the main factor in delaying Japan's surrender in 1945.
After World War II, the American government's main interest in Japan was as a democratic state to counter powers on the Asian continent which was rapidly turning red. So they kept the war-time emperor in power, conveniently ignoring any war crimes he may have been responsible for. Pinning the blame on a small group of insane military men, and thus allowing the Japanese population to avoid blaming the emperor and themselves, the American government aimed to create a country that would serve as a projection of American ideals into Asia. They forget to publicize any evidence they might have had, that the Emperor whom they were propping up might have been the biggest reason for the war, in the interests of stability.
Read the excellent Hirohito and the Making of Modern Japan by Herbert P. Bix. It is eye opening and will destroy any images of a feeble, innocent emperor.