Kōsa

Kennyo Kosa (1543-1591) was the 11th abbot of the Buddhist temple and Ikko-ikki Rebel fortress of Ishiyami Hongan-ji during the late Sengoku period. Kosa allied himself with several powerful clans, being a former ally of warlord Takeda Shingen and later his son Takeda Katsuyori, as well as the Mori clan, with their powerful navy. Kosa also constructed defenses around Ishiyama Hongan-ji, including a series of stone walls and over 50 watchtowers stationed with arquebusiers and archers, as well as a series of tripwires and clay pots intended to break the ankles of horses. Kosa also took advantage of Ishiyama's location, on top of a steep hill with its back to the ocean.

In 1570, Oda Nobunaga laid seige to Ishiyama Hongan-ji, his initial assault consisting of 30,000 men, who he sent to construct fortified staging areas around Ishiyama. These force were ambushed by 3000 Ikko-ikki arquebusiers in a midnight attack which repulsed Oda's armies and destroyed their staging areas. For the first few years, Oda focused on attacking the Ikki's allies and attempting to starve Kosa into submission. This would have probably been successful- Kosa was already considering peaceful negotiations with Oda by 1575.

This was changed, however, when ousted shogun and enemy of Oda's Ashikaga Yoshiaki convinced Mori Terumoto and the powerful Mori clan navy to supply Ishiyama by sea. In 1576, Oda sent 3000 men to attack the fortress. These forces were defeated by 15,000 Ikko-ikki defenders, including arquebusiers, defending 51 outposts around the fortress. With his failure attacking the primary fortress, Oda targeted the outposts and and army under Toyotomi Hideyoshi took one at Negoroji.

In August 1576, Oda's navy under Kuki Yoshitaka were defeated by the Mori fleet at the Battle of Kizugawaguchi. Yoshitaka, however, would return two years later armed with massive atakebune- heavy warships armored with iron plates at least around key areas, and defeated the Mori navy in 1578.

From 1578 to 1580, the Ikko-ikki attempted to break the seige repeatedly, but none of their counterattacks were successful. Kosa finally surrender in 1580 after, running low on ammunition and supplies, received a message from the Emperor of Japan (written while pressured by Nobunaga) asking him to surrender. Kosa surrendered the fortress, and Nobunaga allowed all inhabitants to leave unharmed, though the fortress of Ishiyama Hongan-ji was demolished and replaced with Toyotomi Hideyoshi's Osaka castle a few years later.

Kosa later allied himself with Toyotomi Hideyoshi, with his warrior monks aiding him in defeating the forces of Toyotomi's rival, Shibata Katsuie in 1583, and sent Ikko warriors to guard Toyotomi in Satsuma province. In 1591, Kosa constructed a second temple, Nishi Hongan-ji, in 1591, but died a year later in 1592.