For some time, Minamoto no Yoshinaka had desired to seize control of the Minamoto clan from his cousins Yoritomo and Yoshitsune. Upon returning to Kyoto from his victories at Shinowara and Kurikara, he decided to split from the clan, plotting with Minamoto no Yukiie to kidnap the cloistered Emperor, and establish a government of their own, in the provinces north of Kyoto. But Yukiie did not, in the end, aid Yoshinaka in this scheme. Yoshinaka attacked the Hojujiden (also known as the Hojoji Palace), set it aflame, killed the defenders, and seized the Emperor. He was opposed by quite a number of court nobles and warrior monks from Mount Hiei and Miidera, but ultimately made it out of the city victorious, with the Emperor. However, at this point, the Minamoto armies, under Yukiie, Yoritomo, Yoshitsune, and Noriyori were surrounding the capital. Yoshinaka fled across the Bridge of Uji, where he fought the second Battle of Uji.
References
Sansom, George (1958). 'A History of Japan to 1334'. Stanford, California: Stanford University Press.
Turnbull, Stephen (1998). 'The Samurai Sourcebook'. London: Cassell & Co.