The Jōkyū War of 1221 was the conflict in which Emperor Go-Toba challenged the Kamakura shogunate and suffered defeat.
Go-Toba issued an imperial order calling on warriors to overthrow the Hōjō regent Hōjō Yoshitoki, who effectively controlled the shogunate on behalf of the absent shogun. Many warriors, however, remained loyal to the Kamakura government, which mobilized rapidly and sent a large army west.
Kamakura forces captured Kyoto and defeated the imperial side within weeks. The shogunate exiled Go-Toba and other imperial family members, and it strengthened its authority over the imperial court and western Japan.
The Jōkyū War is sometimes confused with the Genpei War, which ended in 1185 and established Minamoto dominance. It was also different from the Ōnin War, a fifteenth-century conflict that helped begin the Sengoku era.