September 10th 1588 (Tenshō 16)
Donated by the Homma family
This is a letter from Date Masamune (1567–1636), a powerful daimyō in the Tōhoku region, to Oguni Hikojirō, who is thought to have been the feudal lord of Oguni (present-day Tsuruoka City in Yamagata Prefecture) on the borders of Uetsu (referring to Dewa and Echigo Provinces). The letter praises the conquest of Shōnai by Honjō Shigenaga , a vassal of Uesugi Kagekatsu.
In August 1588, Honjō Shigenaga’s army fought the Mogami forces at Jūgorigahara (in present-day Tsuruoka) to regain control of this area. Although the area had been controlled by Mogami Yoshiaki, Shigenaga’s army successfully wrested back control of the area.