The Nanboku-chō period, spanning from 1336 to 1392, was a period that occurred during the formative years of the Muromachi bakufu of Japanese history.
During this period, there existed a Northern Imperial Court, established by Ashikaga Takauji in Kyoto, and a Southern Imperial Court, established by Emperor Go-Daigo in Yoshino.
Ideologically, the two courts fought for fifty years, with the South giving up to the North in 1392. However, in reality the Northern line was under the power of the Ashikaga shogunate and had little real independence.
Since the 19th century the Emperors of the Southern Imperial Court have been considered the legitimate Emperors of Japan. Other contributing factors were the Southern Court's control of the Japanese imperial regalia, and Kitabatake Chikafusa's work Jinnō Shōtōki, which legitimized the South's imperial court despite their defeat.
The consequences of events in this period continue to be influential in modern Japan's conventional view of the Tennō Seika. Under the influence of State Shinto, an Imperial decree dated March 3, 1911, established that the legitimate reigning monarchs of this period were the Southern Court.