was the third son of Nitta Yoshisada

Nitta Yoshisada

was the head of the Nitta family in the early fourteenth century, and supported the Southern Court of Emperor Go-Daigo in the Nanboku-chō period, capturing Kamakura from the Hōjō clan in 1333....

, and a commander of loyalist (Imperial) forces during the Nanbokuchō Wars

Nanboku-cho

The , spanning from 1336 to 1392, was a period that occurred during the formative years of the Muromachi bakufu of Japan's history.During this period, there existed a Northern Imperial Court, established by Ashikaga Takauji in Kyoto, and a Southern Imperial Court, established by Emperor Go-Daigo in...

.

In 1352, Yoshimune led a force from Echigo Province

Echigo Province

was an old province in north-central Japan, on the shores of the Sea of Japan. It was sometimes called , with Echizen and Etchū Provinces. Today the area is part of Niigata Prefecture, which also includes the island which was the old Sado Province. This province was the northernmost part of the...

 to contribute to the loyalist efforts to drive the Shogun, Ashikaga Takauji

Ashikaga Takauji

was the founder and first shogun of the Ashikaga shogunate. His rule began in 1338, beginning the Muromachi period of Japan, and ended with his death in 1358...

, from the city. He defeated Takauji in a number of short engagements, but was eventually driven back to a place called Kotesashi-hara, and then to Echigo.