The Battle of Mimase Pass occurred in 1569 during the Sengoku period. After Yoshimoto Imagawa's death, the alliance between Shingen Takeda and Ujiyasu Hojo broke down, and Shingen decided to strike at the Hojo capital of Odawara. The siege lasted for just five days before Shingen retreated along a treacherous mountain pass, Mimasetoge, and Ujiyasu's inexperienced sons Ujiteru Hojo and Ujikuni Hojo attempted to destroy Shingen's retreating army.
Ujiyasu rushed to the battlefield, where he found that his sons had been split up on opposite corners of the battlefield. Ujiyasu first headed to rescue Ujikuni at Mount Ogura from Kunoichi and Masakage Yamagata's units, and he had Ujikuni withdraw after defeating the Takeda attackers. Shingen attempted to slow the Hojo pursuit of his retreat, shutting several gates and deploying riflemen in battle. However, the Hojo generals Norihide Matsuda and Kuninori Inomata ambushed Shingen in an attempt to hold him back, volunteering their lives to buy Ujiyasu time. Ujiyasu succeeded in advancing to the south and defeating Yukimura Sanada, allowing for him to head southwest from the southeastern castle to catch Shingen, who had locked the west gates of the castle before retreating. The Hojo soldiers bought time for Ujiyasu with their lives, and Ujiyasu was dismayed by the needless deaths of several of his bravest soldiers. Ujiyasu proceeded to defeat Sakon Shima before he could deliver provisions to Shingen, and he then intercepted Shingen and his unit. Shingen was defeated, and, as Ujiyasu prepared to slay Shingen, Shingen asked Ujiyasu to help him march on Kyoto. Ujiyasu ultimately spared Shingen, and they formed an alliance.