Minamoto no Yorimasa (源頼政)(1106-1180) was the leader of the Minamoto armies at the beginning of the Genpei War. While there had been clashes between the Minamoto and Taira clans for decades, Yorimasa, a poet, tried to stay out of politics, and avoided taking sides in this conflict. For a time, he was even friends with Taira no Kiyomori. During the Heiji Rebellion of 1160, he leaned just enough in favor of the Taira that it allowed them to overthrow the Minamoto. However, by the time he officially retired from military service in Kiyomori's army in 1179, Yorimasa had changed his mind about opposing his own clan. In May of 1180, he sent out an appeal to other Minamoto leaders, and to temples and monasteries that Kiyomori had offended.

The Genpei War war officially began with the Battle of the Uji in 1180. Yorimasa led Minamoto forces, along with warrior monks from Miidera, in defending the Byodoin. Despite the monks' having torn up the planks of the bridge leading to the temple, the Taira managed to break through the defenses, and take the temple. Minamoto no Yorimasa's ritual suicide by seppuku is the earliest recorded instance of a samurai's suicide in the face of defeat.

References

Sansom, George (1958). 'A History of Japan to 1334.' Stanford, California: Standford University Press. pp 278-9.