Oda Nobunaga
Consolidation of clan leadership

In spring 1552, Nobunaga faced a new challenge when his uncle, Oda Nobutomo, attacked Nobunaga domain with the support of Shiba Yoshimune, governor of Owari province. Nobunaga repelled the attack and burned the outskirts of his uncle's castle at Kiyosu to discourage further attempts. However, Nobutomo was spared any serious punishment.

In 1553, Hirate Masahide, who had been one of Nobunaga's closest advisors and mentors, committed seppuku. It is generally believed that he did so to admonish Nobunaga, but the actual motive is unclear. Yoshimune tipped off Nobunaga that Nobutomo planned to assassinate him; he was subsequently captured and put to death on the latter's orders. Nobunaga mobilized his forces to blockade Kiyosu castle and set up a lengthy siege.

In 1554, Nobunaga finally achieved victory over the Imagawa clan at the Battle of Muraki Castle, reclaiming the lands he had lost to them. After securing eastern Owari, Nobunaga then turned his attention back to the siege at Kiyosu, where he eventually defeated Nobutomo and forced him to die by seppuku.

In 1556, Saitō Yoshitatsu raised an army against his father, Saitō Dōsan, who was slain in combat at the Battle of Nagara-gawa. Nobunaga set out to Oura in Mino with troops to rescue his father-in-law, but immediately withdrew upon hearing of Dōsan's death. Thereafter, Yoshitatsu usurped his father's title and became lord of Mino.

The loss of the Saitō clan's support further undermined faith in Nobunaga's leadership; key retainers such as Hayashi Hidesada, Hayashi Michitomo, and Shibata Katsuie soon turned on him. They raised an army to support his brother Nobuyuki (Nobukatsu), who was highly regarded within the Oda clan. Nobunaga defeated the rebels at the Battle of Ino, but at the plea of his birth mother, Dota Gozen, pardoned them. Despite his brother Michitomo's death in battle, Hidesada pledged his loyalty to Nobunaga and resumed serving him, while Katsuie chose to remain in Nobuyuki's service.

In 1557, however, Nobuyuki conspired with Oda Nobuyasu, lord of Iwakura Castle, to plot another rebellion. Shibata, disgusted by Nobuyuki's treachery and disloyalty, secretly warned Nobunaga. Nobunaga falsely claimed to have fallen ill and had Nobuyuki and his entourage assassinated when they came to visit him. It is said that either Kawajiri Hidetaka or Ikeda Tsuneoki carried out Nobuyuki's murder.

In 1558, Nobunaga sent an army to successfully protect Suzuki Shigeteru, lord of Terabe Castle, during the Siege of Terabe. Shigeteru had defected to Nobunaga's side from Imagawa Yoshimoto, a daimyō from Suruga Province and one of the most powerful men in the Tōkaidō region.

By 1559, Nobunaga had captured and destroyed Iwakura Castle, eliminated all opposition within the Oda clan, and established his uncontested rule in Owari Province.
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