1569: The Honkoku-ji Incident
Taking advantage of Nobunaga's absence in Gifu, the Miyoshi Triumvirate led an army of 10,000 to attack Honkoku-ji, the temporary residence of shogun Ashikaga Yoshiaki. The defenders, including Akechi Mitsuhide, held out with reinforcements arriving from allied commanders, and upon hearing the news Nobunaga reached Kyoto in a mere two days. The Miyoshi forces were repelled, and Nobunaga subsequently began building a proper fortified residence (Nijō Castle) for Yoshiaki.
Events this year
Oda Nobunaga expanded the former Buei encampment and built a fortified Nijō palace for Ashikaga Yoshiaki, who had become shogun the previous year.
Takeda Shingen attacked Odawara Castle, but Hōjō Ujimasa held the fortress. The conflict between Hōjō and Takeda deepened.
Following Takeda Shingen's invasion of Suruga, Hōjō Ujiyasu and Ujimasa pursued peace with their longtime enemy Uesugi Kenshin. The two houses formed the Etsusō Alliance to oppose the Takeda.
Sources おだわらデジタルミュージアム「北条氏康書状（永禄12年3月13日）」