From 1888 to 1945, "Kimigayo" served as the national anthem of the Empire of Japan. When the Empire was dissolved following its surrender at the end of World War II, the State of Japan succeeded it in 1945. This successor state was a parliamentary democracy, and the polity therefore changed from a system based on imperial sovereignty to one based on popular sovereignty. However, the U.S. occupation forces allowed Emperor Hirohito to retain the throne and "Kimigayo" remained the "de facto" national anthem. The passage of the Act on National Flag and Anthem in 1999 recognized it as the official national and imperial anthem.