1563: The Outbreak of the Mikawa Ikkō-ikki
Kūshō, the head priest of Honshō-ji in Mikawa, rallied followers, and an Ikkō-ikki uprising against Matsudaira Ieyasu (the future Tokugawa Ieyasu) erupted across western Mikawa. Some of Ieyasu's own hereditary retainers, including Honda Masanobu, joined the rebels, splitting his vassal band. The six-month revolt was later counted by Ieyasu himself among the three greatest crises of his life.
Events this year
Oda Nobunaga built Komakiyama Castle as a base for his campaign into Mino, moved there from Kiyosu, and developed a planned castle town below the mountain.
Tokugawa Ieyasu's forces clashed with followers of the Honganji school centered on Mikawa's three major temples, and his retainers split between the two sides. The conflict continued until a settlement and suppression in spring 1564.
Sources 岡崎市「歴史文化の特徴」／安城市図書情報館「新編安城市史5 細目次」／岡崎市「市指定：史跡 上宮寺境内地」／愛知県総合教育センター「三河一向一揆と本證寺」
Mōri Takamatsu died suddenly during an expedition to Izumo, and his grandson Terutoto succeeded to the headship. Motonari became Terutoto's guardian.
Kūsei, abbot of Honshōji, and forces including Hatoya Hannosuke, based at Shōmanji, barricaded themselves in a fortified temple town and confronted Tokugawa Ieyasu's forces.
Sources 安城市「本證寺境内」／岡崎市「市指定：史跡 勝鬘寺境内地」