Yoshitsugu was the son of Nihonmatsu Yoshikuni. He was hard-pressed by Date Masamune and in the autumn of 1585 called on Masamune's retired father, Terumune, to intercede and make peace. When Terumune and Yoshitsugu met, however, Yoshitsugu kidnapped Terumune at sword-point. Whether Yoshitsugu had planned beforehand to carry out this incredible act is unclear. When Masamune was alerted to the double-cross he rode hard after Yoshitsugu's party. In the confrontation that ensued, Terumune and Yoshitsugu were killed. Another version of events, however, states that Yoshitsugu in fact escaped back to Nihonmatsu castle. Masamune attacked Nihonmatsu the following year and the Hatakeyama accepted an offer of surrender brokered by the Sôma family. Yoshitsugu's life, however, was forfeit and Masamune had his head exposed.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005