Jōkyū War
The establishment of the Kamakura shogunate is taken to mark the beginning of the Kamakura period, but the Insei system was not immediately abandoned. Though the shogunate took over the police force and ruled eastern Japan, the authority of the emperors and retired emperors remained considerable. However, when Go-Toba, a grandson of Go-Shirakawa, sought to overthrow the Kamakura shogunate, his forces were defeated in the Jōkyū War, and the shogunate then took steps to reduce the power (and the finances) of the retired emperors. Even after the Jōkyū War, the cloistered rule system continued to exist, at least formally, for another 200 years. There were movements to take authority back into the hands of the imperial court, such as the Kenmu Restoration attempted by Emperor Go-Daigo, but in general a retired emperor presided as the head of the Kyoto court, with the approval of the shogunate.