The Battle of the Nakatomi-gawa River (中富川の戦い)
The Battle of the Nakatomi-gawa River, in 1582, was a battle between Motochika CHOSOKABE, a lord of Tosa Province, who intended to integrate the Shikoku region, and Masayasu SOGO, a lord of Awa Province. It is also called the Battle of Kawanakajima in Shikoku.
Motochika CHOSOKABE had his troops stand by to prepare against the expedition to Shikoku by Nobunaga ODA. However, the crisis passed away when Nobunaga ODA was killed by Mitsuhide AKECHI in the Honno-ji Incident and Yasunaga MIYOSHI left for Kinai region. Chikayasu KOSOKABE, a younger brother of Motochika and Nobuchika CHOSOKABE, a legitimate child of Motochika put their troops forward to capture Shozui-jo Castle after seizing Ichinomiya-jo Castle (Awa Province) and Ebisuyama-jo Castle. After that, having a council of war including ichiryo gusoku, the self-made rural samurai, they aimed to take complete control of Awa Province. Motochika collected people aged from 15 to 60, who could participate in the war to raise his troop strength.
The Battle of the Nakatomi-gawa River
On September 24, they opened fire at the Nakatomi-gawa River (Chosokabe force 23000, Sogo force 6000). Most people expected the Sogo force to have confined themselves in the Shozui-jo Castle. However, the Sogo force chose field battle. As soon as the van of the Sogo force crossed the river, the Chosokabe force broke the dam, which they already had built to stop the flow upstream. The flash flood swept away many Sogo soldiers. After that, the Sogo force was routed and retreated into Shozui-jo Castle.