In 1940, during the second World War, coinciding with their ally Germany's invasion of France, the Japanese invaded French Indochina.
The Japanese promised not to interfere with the court at Huế, but in 1945, after ousting the French, coerced Bảo Đại into declaring Vietnamese independence from France as a member of Japan's "Greater East Asia Co-Prosperity Sphere"; the country then became the Empire of Vietnam.