The Battle of Nagamorihara occurred in Eishō 7 (1510) in Nagamorihara in Echigo Province.  The battle was waged between the forces of Nagao Tamekage and Uesugi Akisada to determine the military governor of Echigo.

Background

Uesugi Fusayoshi was a shugo daimyō, the military governor of Echigo, and the seventh head of the Echigo-Uesugi family.  In the sixth month of 1503, Uesugi Sadazane received as his formal wife the daughter of Fusayoshi so that Sadazane became Fusayoshi’s son-in-law.  In the eighth month of 1507, Nagao Tamekage, the deputy military governor and sengoku daimyō of Echigo, gave support to Sadazane to oust Fusayoshi.  On 11/6 of 1508, Sadazane became the military governor but in fact was a puppet of Tamekage.  Around this time, Sadazane wed the younger sister of Tamekage.  His formal wife (Fusayoshi’s daughter) is believed to have died as of this time.  Usami Fusatada presented Sadazane with a prized sword inscribed with the name of Usami Sadamitsu.

To avenge the removal of Fusayoshi from his position, Uesugi Akisada (the deputy shōgun for Kantō and older brother of Fusayoshi) invaded Echigo, whereupon, in 1509, Sadazane and Nagao Tamekage fled in defeat to neighboring Etchū Province.  Having seen that Akisada’s army could not garner the support of the kokujin, or families of influence, in Echigo, on 4/20 of 1510, Tamekage and Sadazane traveled from Etchū via Sado Province to land in a harbor named Kanbara-no-tsu.  With additional soldiers from Sado, Tamekage’s forces had regained their strength and defeated Akisada’s army across Echigo.  While Akisada’s army attempted to retreat, Tamekage pursued them and one of the reinforcements named Takanashi Masamori killed Akisada, enabling victory for Tamekage’s army.  In addition to the death of Akisada himself, Akisada’s army suffered a major defeat including the loss of Nagao Sadaaki and other commanders.