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
Month 5
Tokugawa Ieyasu besieged Kakegawa Castle for six months, where Imagawa Ujichika had fled after being pursued by Takeda Shingen. Ujichika surrendered the castle and lost his domain as a daimyo.
Sources 掛川市「掛川城の歴史」
8/26
Oda Nobunaga attacked Kitabatake Tomonori, provincial governor of Ise, at Ōkōchi Castle. After surrounding it with multiple palisades and besieging it for roughly fifty days, a settlement was reached whereby Nobunaga's third son became the adopted heir of Kitabatake Tomonori, effectively bringing the Kitabatake clan under Nobunaga's control.
Sources 三重県「大河内城の戦いと信長の伊勢進攻」
Month 10
Takeda Shingen led a large army to besiege Odawara Castle in Sagami. While withdrawing from the siege to return to Kai, his forces clashed with the Hōjō, resulting in the Battle of Mimase Pass.
Sources 小田原市「新・北条五代記 四代氏政の時代」
As the Takeda army retreated toward Kai after lifting the siege of Odawara Castle, the Hōjō pursued them, resulting in a battle at Mimasaka Pass. According to Aikawa Town's account, the Hōjō initially had the upper hand, but when Yamamoto Kagesuke's unit launched a surprise attack from higher ground, the situation changed in favor of the Takeda, who ultimately won. Casualty figures of 3,269 for the Hōjō and 900 for the Takeda are presented, but these are traditional estimates provided by the town and not confirmed figures.
Sources 愛川町「三増合戦史跡」
Month 11
The Takeda army laid siege to Fukasawa Castle, a strategic strongpoint connecting Suruga, Sagami, and Kai, which surrendered in the first month of Genki 1 the following year.
Sources 静岡県「しずおか文化財ナビ 深沢城跡」
Oda Nobunaga expanded the former Buei encampment and built a fortified Nijō palace for Ashikaga Yoshiaki, who had become shogun the previous year.
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）」