Japan's ancient, indigenous religion, premodern Shinto, was considered one of the world's least dogmatic, laidback belief systems. Many of its earthy, animist rituals were tied to a love of nature and tradition, anchored around festivals and ceremonies honoring kami (gods) found in all aspects of life.

After the Meiji Restoration of 1868, Shinto was retooled for the modern, bureaucratic state. The first reformists purged Buddhism, made Shinto a state religion and elevated the Emperor to head of state, making him the divine link in an unbroken chain going all the way back to the sun goddess.

As such, the religion became inextricably bound up with the rise of Japanese nationalism and its central tenets. The Emperor had a divine right to rule Japan, which was superior to other nations. Millions of Japanese children were taught these supremacist beliefs, fueling the clash with foreign imperialisms.