Japanese Rising Sun Flag Patch. The flag of the Rising Sun was originally used throughout feudal Japan, and during the Meiji Reformation it became the official battle flag for the new imperial military. The Empire of Japan used the Rising Sun flag for official functions, as naval jacks, and army banners, and it is often the symbol of Japan during World War Two. It is still in use as the official ensign of the Japanese Maritime Self-Defense Force (JMSDF).