However, after Honshu-ji Temple in Toro (Okazaki City) was founded by the 8th head priest Rennyo, the influence of the Jodo Shinshu Honganji sect spread rapidly.

[1] On 15 February 1564, Motoyasu had decided to concentrate his forces in eliminating the Ikki from Mikawa and had sought the help of warrior monks from the temple of Daiju-ji with whom he enjoyed good relations.

The battle was fierce and Motoyasu took the field personally, issuing challenges to enemy samurai and fighting in the front line where he received several bullets that pierced his armour but failed to wound him.

[citation needed] Throughout most of history, it was thought that this war of suppression was a sign of Tokugawa Ieyasu religious intolerance towards Jōdo Shinshū Buddhism which practiced and observed by Ikkō sect.

This further complicated the situation by the fact that not only Ieyasu's own vassals, but this religious uprising also brought on other Mikawa local lords such as Kira Yoshiaki and Yoshihiro Arakawa.

[4] Historian Hamada Kōichirō stated that there is a theory that Ieyasu intentionally orchestrated the Ikkō-ikki uprising to break out, so the Tokugawa clan has Casus belli to launch military campaign in their effort to centralize control of Mikawa.