information:highlighting, structural:summarization, linguistic:paraphrasing, structural:reformatting, structural:scholar_edition
Succession crisis

In 1551, Oda Nobuhide died unexpectedly. It has been said that Nobunaga acted outrageously during his funeral, throwing ceremonial incense at the altar. Although Nobunaga was Nobuhide's legitimate heir, a succession crisis occurred when some of the Oda clan opposed him. Nobunaga assembled a force of 1,000 men and used them to intimidate and dissuade his enemies, thus preventing a serious disruption in the transfer of power.

Sensing weakness, the daimyō Imagawa Yoshimoto sent an army under the command of Imagawa Sessai to lay siege to the castle at Anjō, where Oda Nobuhiro, Nobunaga's older brother, was living. To save his life, Nobunaga was compelled to turn over a hostage held by his clan at Honshōji temple, nine-year-old Matsudaira Takechiyo – later known as Tokugawa Ieyasu – an exchange that helped solidify an alliance between other rival clans. Nobuhiro, frustrated by his low standing in the Oda clan, later plotted against Nobunaga with the assistance of another rival, Saitō Yoshitatsu; Nobunaga learned of the plot but chose to forgive his brother's problem.

In early 1552, barely several months after his father's death, one of Oda's senior retainers, Yamaguchi Noritsugu and his son Yamaguchi Noriyoshi defected to the Imagawa clan. In response, Nobunaga attacked Noritsugu, but was defeated by Noriyoshi's forces at the Battle of Akatsuka; he retreated and left contested lands in eastern Owari under Imagawa control.