On the fourteenth day of the fifth month in 1221, the retired Emperor Gotoba used a mounted archery competition as a pretext to gather samurai warriors together from all over the country, until he had assembled an army of over 1700 mounted samurai, including those in the Northern and Western Guard Corps and those official guardsmen stationed in Kyoto.
同年5月14日、後鳥羽上皇は「流鏑馬揃え」を口実に諸国の兵を集め、北面・西面の武士や近国の武士、大番役の在京の武士1700余騎が集まった。