- Japanese: 征西府 (Seiseifu)
The Seiseifu (roughly, "office for the subjugation of the west") was, ostensibly, the chief headquarters of the Imperial Court in Kyushu in the medieval period. Amidst the political divisions of the Nanboku-chô period, however, it became in practice a major center of strength for supporters of the Southern Court, standing in opposition to the forces of the Northern Court. In particular, in the 1360s-1380s, the Seiseifu (and by extension the island of Kyushu) was ruled by Prince Kanenaga (aka Kaneyoshi) and his wakô allies.
When at the peak of its power, from 1360 to 1372, the Seiseifu was based at the former site of the Dazaifu. It then moved to a site called Kikuchi, in the mountains of Higo province until 1381, after which it relocated to Take, Uto, and finally Yatsushiro, all within Higo province, finally remaining in Yatsushiro until 1390.
Kanenaga, a son of Emperor Go-Daigo, was formally named seisei shôgun (General for the Subjugation of the West), and gained the support of most if not all of the samurai clans of Kyushu, and a certain degree of de facto power over the entire island by 1365. Bolstered by material supplies looted from coastal Korea by his wakô allies, Kanenaga quickly began exchanging envoys with the Ming court, even being invested as "King of Japan." Historian Amino Yoshihiko describes this as Kanenaga attempting (and perhaps succeeding, to some extent, however briefly) "to establish an independent country in Kyushu."
Kanenaga's independent power in Kyushu came under attack in the 1370s, however, by forces led by Imagawa Ryôshun, Kyushu tandai in service to the Northern Court and the Muromachi shogunate. Kanenaga's son Prince Yoshinari took over de facto leadership of the Seiseifu in 1375; though the Seiseifu continued to resist Imagawa's advances until Kanenaga's death in 1383, the shogun meanwhile received investiture from the Ming as "King of Japan," thus stripping Kanenaga of that recognition as well. Yoshinari continued to lead after his father's death, but in 1392 the Northern and Southern Courts reunited, and the Nanboku-chô period of division was ended.
- Amino Yoshihiko, Alan Christy (trans.) Rethinking Japanese History, Center for Japanese Studies, University of Michigan (2012), 269-270.
- Gregory Smits, Maritime Ryukyu, University of Hawaii Press (2019), 46-48.
- Amino, 270.