The Siege of the Sanjo Palace was the primary battle of the 1159 Heiji Rebellion. In early January of 1160, after Taira no Kiyomori left Kyoto on a family pilgrimage, Fujiwara no Nobuyori and Minamoto no Yoshitomo saw an opportunity to effect changes they sought in the government. With a force of roughly five hundred men, they attacked in the night, kidnapping the former Emperor Go-Shirakawa, and setting fire to the Palace. They also abducted and imprisoned the current Emperor, Nijō, who supported their enemies, the Taira clan and Fujiwara no Michinori .

They next attacked the manor house of Michinori, setting it too aflame and killing all those inside, with the exception of Michinori himself, who was captured later and decapitated. Nobuyori forced Emperor Nijo to name him Imperial Chancellor, completing one of the first important steps towards gaining power over his rivals.

However, Taira no Kiyomori returned soon afterwards, with his son Taira no Shigenori and a small force. The Minamoto, reinforced with men from Kamakura led by Yoshitomo's eldest son Minamoto no Yoshihira, were the larger force but were unprepared, and hesitated at Kiyomori's return. The Taira were thus allowed to return to their family's mansion in the Rokuhara district, where they would plan tactics and strategies, and gain many more warriors.

At the end of January, the Taira smuggled the Emperor Nijo and his Empress out of the Sanjo Palace and into the Rokuhara mansion, disguised as a lady in waiting. Meanwhile, the Taira also helped the former Emperor, Go-Shirakawa, escape from the Minamoto as well.

On the morning of February 5th, Minamoto no Yoshitomo and his men prepared to defend the Palace against the inevitable Taira assault. The defense held out for a time, until a portion of the Taira feigned a retreat, luring Minamoto warriors out of the Palace, and giving the rest of their force an opportunity to rush the Gates and, soon afterwards, drive the Minamoto out. Yoshitomo's men were then obliged to attack the Rokuhara mansion, but failed in their assault, and fled Kyoto, meeting resistance along the way from the warrior monks of Mount Hiei who they had attacked in decades past.

References

• Sansom, George (1958). 'A History of Japan to 1334'. Stanford, California: Stanford University Press.