The Ishiyama Hongan-ji (石山本願寺) was the primary fortress of the Ikkō-ikki, leagues of warrior priests and commoners who opposed samurai rule during the Sengoku period.

Rennyo, the great revivalist abbott of Jōdo Shinshū (Ikkō-shū), retired to the area in 1496, initiating the series of events that would end in the formation of Japan's second-largest city.

Contemporary documents describing his retirement site as being on a "long slope" (大坂, Ōzaka) are the first to call the area by that name, which has changed only slightly over time to Osaka (大阪), and become Japan's second largest city.

After the 1532 destruction of Yamashina Mido in Kyoto, the Ishiyama Hongan-ji acted as the primary temple for the Ikkō sect, from which the Ikkō-ikki had sprouted.

In addition, roughly a hundred priests were on patrol at any given time, and upwards of ten thousand could be summoned to battle simply by ringing a bell.