The Siege of Odawara occurred in 1561 during the Sengoku period. In alliance with the Imagawa and Takeda clans, Ujiyasu Hojo expanded into Echigo Province and displaced local rulers, who pleaded to Kenshin Uesugi for assistance. Kenshin responded by taking castle after castle, and a combined army of 113,000 Uesugi and allied soldiers laid siege to Odawara Castle in Sagami Province.
The Uesugi forces succeeded in breaching the castle, but Ujiyasu entrusted the defense of the main ward to Tsunashige Hojo and decided to personally lead a counterattack. Ujiyasu drove the Uesugi generals Nagayasu Narita, Sukemasa Ota, and Tsunahide Mita from the inside of the castle, pushing the Uesugi forces within the walls outside of the castle. The Uesugi vanguard, led by Aya, advanced towards the castle after Ujiyasu gave orders for his army to man the castle defenses, but Ujiyasu succeeded in destroying the vanguard. Soon, local peasants reported the arrival of an enemy transport convoy, so Ujiyasu decided to escort them to Tsunashige; he defeated Masatsuna Sano before he could slaughter them. Kenshin Uesugi then received reinforcements, and he decided to order an all-out attack on the main ward. Just then, Shingen Takeda arrived with Takeda reinforcements for Ujiyasu, who believed that Shingen wanted a favor in return. The combined armies went on to defeat Kenshin, who was forced to withdraw.