Kōji was an era from 10/23 of 1555 to 2/28 of 1558 (based on the Japanese lunisolar calendar) in the Sengoku period. The preceding era of Tenbun was changed to Kōji in response to calamities including ongoing conflicts.
The Kōji era witnessed a transition from Emperor Gonara (the 105th emperor) to Ōgimachi (the 106th emperor). During this era, Ashikaga Yoshiteru served as the thirteenth shōgun of the Muromachi bakufu, with a tenure that began in 1546 and ended in 1565 at the youthful age of twenty-nine after an attack on his palace in Kyōto by Matsunaga and Miyoshi forces.
Key events and battles
From 1555 to 1558, there was a large-scale rebellion by provincial families in Mikawa against the Imagawa clan, an event known as the Mikawa sōgeki, or the Furious Drama of Mikawa.
In the autumn of 1555, just prior to the change in the name of the era to Kōji, Mōri Motonari defeated Sue Harukata at the Battle of Itsukushima in Aki Province.
In 1556, Saitō Yoshitatsu, the daimyō of Mino Province, defeated and killed his father, Saitō Dōsan, at the Battle of Nagaragawa.
In 1557, opposing armies led by Takeda Harunobu (Takeda Shingen) of Kai Province and Nagao Kagetora (Uesugi Kenshin) of Echigo Province clashed in the Third Battle of Kawanakajima in Shinano Province.
Uesugi Kagekatsu. One of Five Elders in the Toyotomi administration and the first lord of the Yonezawa domain of Dewa Province in the Edo period.
Tōdō Takatora. Served as a bushō and daimyō. In the Edo period, served as head of the Imabari domain in Iyo Province and first head of the Tsu domain in Ise Province.
Katagiri Katsumoto. Served as a bushō and daimyō. A member of a distinguished group of warriors known as the Seven Spears of Shizugatake. During the Edo period, served as the first head of the Tatsuta domain in Yamato Province.
Taigen Sessai. A monk in Suruga Province.
Takeno Jō-ō. A tea master in Sakai in Izumi Province.
Suwago-ryōnin. Consort of Takeda Harunobu (Shingen) and mother of Takeda Katsuyori.
Saitō Dōsan, the sengoku daimyō of Mino Province.