The Kenkyu War (named for the Kenkyu Era of April 1190-April 1199) was a war in Japan caused by the realm divide of the Kamakura Minamoto. Fearful of the rise to prominence of the Kamakura Minamoto, Emperor Go-Toba declared Minamoto Yoritomo an enemy of the state and called upon every clan in Japan, including Minamoto vassals, to fight against Yoritomo's building empire. Some clans, such as the Ishikawa, stood loyal to the Kamakura Minamoto clan, while the majority of Yoritomo's vassals and allies betrayed him to fight for the Emperor.
Background[]
The Kamakura Minamoto clan emerged victorious in the Genpei War against the Taira clan after the Battle of Dan-no-Ura in 1185, although they faced small remnants up until 1188. Minamoto Yoritomo was just as much a master of strategy as a master of politics and intimidation. Through diplomacy, he had forced many clans to become his vassals or allies, while also fighting those who refused Minamoto suzerainty.
Power bred fear among the weak. Fearful of their strength and influence, the imperial family declared them enemies of the state. The Minamoto had to be prepared; no one could be relied upon to aid them, not even their sister family, the Kiso Minamoto. First to declare war on the Minamoto were the Hiraizumi Fujiwara, but the Fukuhara Taira, Kiso Minamoto, Yuki, Yamauchi, Ogata, Hasebe, Kyogoku, Nitta, Ariwara, and Kubota Fujiwara stood loyal to Yoritomo. Soon, the Ii joined the anti-Minamoto alliance, facing Yoritomo, Kyogoku, Nitta, Kikuchi, Ishikawa, Kubota Fujiwara, Yuki, Hatakeyama, Akamatsu, Ariwara, and Ogata. The third clan to declare war were the Satake, facing Yoritomo and the allies.
Great Kenkyu War[]
The Yamauchi were destroyed relatively early in the conflict, and many of the Minamoto allies began to desert, chief among them the Kubota Fujiwara, Shinmen, and Honda. The Kubota had Minamoto Tanefusa, the second son of Yoritomo, executed as they prepared for renewed war.
The first major battle was the Shinmen clan's invasion of Kyoto, carried out by daimyo Shinmen Munehisa and his son and heir Shinmen Nobukata and Suda Nagashige. With 8,000 troops, the Shinmen overran Togakure Tokimochi's 3,000 Minamoto villager militia with ease, and the Hatakeyama, led by Kagemitsu, declared war on the Minamoto due to the inspiration.
Ii Sanemasa, Yokota Ujizane, Yamaoka Tomotada, and Akagawa Korenobu, all of the Ii clan, invaded Mikawa Province and captured the lands from the Minamoto. Soon after, the Fukuhara Taira, loyal to the Minamoto, were conquered by the Imperial forces. But the Minamoto forces rallied and the Ishikawa conquered the Honda, decimating Honda Yoshinatsu.
Meanwhile, Minamoto Mitsunao recaptured Kyoto and forced the Shinmen to become their vassals. The Shinmen aided them in their war against the Isonokami and the other enemies of northern central Honshu while Mitsunao was free to take over many of the northern coastal regions. In the process, he was able to set up the Kusunoki clan as vassals; they would play a major role in 14th-century Japanese politics. Despite Mitsunao's successes, fortunes fell for the Minamoto on the front to the north in the war with the Fujiwara. Despite his success at eliminating Fujiwara Motofusa's army along with his generals, Mitsunao lost most of his men and Fujiwara Chikakage took back Miyagi Province by assault, killing Yoritomo and Saito Kanenaka in the process. The Minamoto lost all of their northern provinces, and although they managed to conquer the Yuki and Satake clans, they faced unrest in their Chugoku regions and Kyoto was captured by a combined Isonokami and Hatakeyama army in 1191.