Tomosada was the son of Uesugi Tomooki. He lost Kawagoe castle to Hôjô Ujitsuna in 1537 and was forced to retreat to Matsuyama castle. He allied with Uesugi Norimasa (of the Yamanouchi-Uesugi) and together they made a series of bids to retake Kawagoe. Their greatest effort occured in 1544, when they had the support of Ashikaga Haruuji and the Hôjô were distracted by the Imagawa family. The allies surrounded Kawagoe, and when Ujiyasu suggested a truce, Tomosada flatly refused (some say with a laugh). Tomosada and his allies grew ever more overconfident, assuming Ujiyasu's request was one of desperation (which it may have been at the time), and let their guard begin to slip. Tomosada was killed the following year in a surprise Hôjô night attack that saved the castle. With his death, the Ogigayatsu-Uesugi declined rapidly.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005