Taijoko (retired emperor) (太上皇)
The Taijoko is the honorary title given to a retired emperor or empress in his or her life.
'Taijo' means the 'highest.'
It is also referred to as joko (retired emperor) in Japan. For joko in Japan, refer to the Daijo Tenno section. The empress of a taijoko is called kotaigo (empress dowager) or taikotaigo (grand empress dowager).
China
Chinese taijoko are the Emperor Hui in West Jin (West Jin), Li Yuan in Tang, Yejong (Tang), Xuan Zong (Tang), Gao Zong in Southern Sung (Sung), Yingzong of Ming (Ming), Qian Long of Ching, etc. Also, examples of taijoko who did not ascend to the throne himself but was granted the title posthumously or in life because his child became an emperor and founded a dynasty, as in the case of the Japanese Cloistered Emperor Gotakakura, are the King Zhangxiang, who was the father of the first Qin Emperor, and Liu Taigong, who was the father of Liu Bang of Han.
Korea
In the Yi Dynasty Korea, Gao Zong (the King of Korea) designated the name of the country to the Korean Empire, and became the first Korean emperor. Amid the intervention by neighboring countries, he adopted the pro-Russian policy and tried to exclude the intervention by Japan. One symbolic episode is the Hague Secret Emissary Affair, in which Korea tried to exclude Japanese rule by demonstrating its illegitimacy to the international community, but the trial failed and the Korea-Japan relationship deteriorated. On this occasion, Lee Wan-yong and other pro-Japanese people planned to depose the emperor, who was forced to pass the throne on to the crown prince on July 20 and become a retired emperor. He was the last retired emperor among East Asian taijoko or daijo tenno (both meaning retired emperor).
Vietnam
In Vietnam, the title of taijoko was different from those in China or Korea, and meant the title of the monarch only in domestically.
Although successive dynasties had paid tribute to the Chinese Emperors for generations, the Vietnamese emperors were unwilling to be treated as a vassal by disclosing their real names to other countries. Such background brought about the custom under which an emperor would pass the throne on to the successor at an early stage, and became a retired emperor to act as the top decision maker and dealt with foreign policy (China), while the new emperor dealt with domestic affairs. In that context, the tribute to the Chinese court was conducted by the retired emperor under the name of the 'king,' and it is said that the reigns of Vietnamese monarchs according to the Chinese historiography and Vietnamese historiography are one generation out of synchronization.