Nobesawa Mitsunobu served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a retainer of the Mogami clan and served as the second lord of Nobesawa Castle in Dewa Province.
In 1544, Mitsunobu was born as the son of Nobesawa (Satsuma-no-kami) Mitsushige. In 1547, Mitsushige constructed Nobesawa Castle and served as its first lord.
As an ally of the Tendō clan, the Nobesawa were members of an alliance of powerful kokujin, or provincial landowners, in Dewa known as the Eight Shields of the Mogami (or, as the Eight Shields of the Tendō). The Nobesawa managed the Nobesawa-Ginzan, a silver mine located within their territory.
Mitsunobu was known for his prowess on the battlefield and, together with the Tendō clan, fought over a long period of time against Mogami Yoshiaki, the lord of Yamagata Castle, frequently defeating his forces. To compel the surrender of the members comprising the Eight Shields of the Mogami, Yoshiaki concluded that he needed to subdue Mitsunobu. In 1584, Yoshiaki arranged for the marriage of his daughter, Matsuohime, to Mitsunobu’s son, Matagorō, thereby removing Mitsunobu from the ranks of his opposition. As a condition of surrender, Mitsunobu requested Yoshiaki to spare the life of Tendō Yorizumi. In the absence of Mitsunobu, the Eight Shields of the Mogami collapsed and Tendō Castle fell. As earlier promised, however, Yorizumi was permitted to escape to the protection of Kokubun Morishige, the father of Yorizumi’s mother. That same year, Yoshiaki slayed Shiratori Nagahisa, the lord of Yachi Castle, and decimated his clan. A portion of those landholdings was allocated to Mitsunobu.
In the eleventh month of 1590, Mitsunobu followed orders from Yoshiaki to travel to Kyōto but fell ill and, on 3/14 of Tenshō 19 (1591), died in the capital. He was forty-eight years old.
Aware of Mitsunobu’s renowned strength, Yoshiaki aimed to test him by gathering seven or eight hearty individuals from the family to lie in ambush in the garden, but Mitsunobu quickly shook off every one who attempted to assault him. Surprised at the outcome, Yoshiaki clung to a large cherry tree in an effort to escape, but Mitsunobu pulled on Yoshiaki so hard that, in the midst of the struggle, the tree was torn from its roots and fell down along with Yoshiaki.