1589: Battle of Suriagehara and Rising Tensions in the Northern Provinces - Sengoku Shogun Map
Date Masamune defeated the Ashina at Suriagehara and captured Kurokawa Castle in Aizu. The balance of power in the north collapsed, heightening tensions that would lead to the Odawara Campaign the next year and the Pacification of Oshu the following year. Meanwhile, the Toyotomi regime advanced land surveys (kenchi) and central control.
Major events
- 1589-06: Battle of Suriagehara — Date Masamune defeated the forces of Ashina Yoshihiro at Suriagehara and subsequently entered Kurokawa Castle, taking control of Aizu.
- 1589-月日不詳: Expansion of Yamanaka Castle — The Later Hōjō strengthened Yamanaka Castle against an anticipated conflict with Toyotomi Hideyoshi, including the addition of the Daisaki outer enclosure.
- 1589-10: Seizure of Nagurumi Castle — Inomata Norinao, the Later Hōjō castellan of Numata, seized Nagurumi Castle, which Toyotomi Hideyoshi's settlement had assigned to the Sanada.
- 1589-11-24: Hideyoshi Declares War on the Later Hōjō — Toyotomi Hideyoshi treated the seizure of Nagurumi Castle as a violation of his peace order and issued a declaration of war to Hōjō Ujinao.