[1][2] At the time when the seventeen-year-old Oda Nobunaga inherited family estates (of the so-called Shibata branch of Oda family, though Shobata Castle, built before 1520 by his grandfather, was abandoned in 1538) in the southwestern part of Owari Province (around Nagoya Castle) in spring of 1552, the southern parts of the province were ruled by his cousins, Oda from Kiyosu Castle, and the eastern parts of Owari were ruled by the powerful Imagawa clan, who at the time ruled the neighboring provinces of Mikawa, Totomi and Suruga, and their vassals, the Matsudaira clan (later Tokugawa) from Mikawa.

[1][2] Next year, on July 12, 1553, Oda Nobutomo executed the legal governor (shugo) of the province, Shiba Yoshimune, who lived as a glorified hostage at his castle, for conspiring with Nobunaga.

Retainers of Kiyosu suffered significant losses (more than 30 prominent samurai), but Nobunaga did not dare to attack the castle, so left it under a blockade, waiting for the opportunity to take it by cunning.

Nobumitsu apparently agreed to betray Nobunaga, and with a group of warriors he was released in Kiyosu, but during the night his men opened the gates and the castle was conquered by storm (April 20, 1554).

Oda Nobutomo was forced to commit seppuku, while Sakai Dozen managed to escape to the province of Suruga, finding refuge with Nobunaga's archenemy, Imagawa Yoshimoto.