After two years, when Ōishi was convinced that Kira was thoroughly off his guard, and everything was ready, he fled from Kyoto, avoiding the spies who were watching him, and the entire band gathered at a secret meeting place in Edo to renew their oaths.
In Genroku 15, (1702) 14 December (元禄十五年十二月十四日),early in the morning in a driving wind during a heavy fall of snow, Ōishi and the other rōnin attacked Kira Yoshinaka’s mansion in Edo. According to a carefully laid-out plan, they split up into two groups and attacked, armed with swords and bows. One group, led by Ōishi, was to attack the front gate; the other, led by his son, Ōishi Chikara, was to attack the house via the back gate. A drum would sound the simultaneous attack, and a whistle would signal that Kira was dead.
Once Kira was dead, they planned to cut off his head and lay it as an offering on their master’s tomb. They would then turn themselves in and wait for their expected sentence of death.All this had been confirmed at a final dinner, at which Ōishi had asked them to be careful and spare women, children, and other helpless people.
Ōishi had four men scale the fence and enter the porter’s lodge, capturing and tying up the guard there.He then sent messengers to all the neighboring houses, to explain that they were not robbers but retainers out to avenge the death of their master, and that no harm would come to anyone else: the neighbors were all safe. One of the rōnin climbed to the roof and loudly announced to the neighbors that the matter was an act of revenge (katakiuchi, 敵討ち).
The neighbors, who all hated Kira, were relieved and did nothing to hinder the raiders.