After defeating the forces of the Tokugawa shogunate at the Battle of Toba–Fushimi, the Imperial forces (consisting of the feudal armies of Chōshū, Satsuma and Tosa domains) split into three columns, which progressed northeast towards the Tokugawa capital of Edo up each of the three main highways: Tōkaidō (road), Nakasendō and Hokurikudō.

Kondō created a new unit based on the surviving remnants of the Shinsengumi, called the Kōyō Chinbutai (甲陽鎮撫隊, Pacification Corps), and they departed Edo on 24 March.

The Imperial army then met the Shogunal forces in battle at Katsunuma (now a part of Kōshū, Yamanashi) on 29 March.

The survivors, including Kondō, attempted to flee to Aizu via Sagami Province, which was still controlled by Tokugawa hatamoto loyalists.

The Battle of Kōshū-Katsunuma was the last significant military action in central Honshū during the Boshin War, and the death of Kondō Isami further demoralized Tokugawa supporters, contributing to the surrender of Edo Castle without bloodshed later that year.