The destruction of the Kamakura shogunate of 1333 and the failure of the Kenmu Restoration in 1336 opened up a legitimacy crisis for the new shogunate. Furthermore, institutional changes in the estate system (the "shōen") that formed the bedrock of the income of nobles and warriors alike decisively altered the status of the various social groups. What emerged from the exigencies of the Nanboku-chō (Southern and Northern Court) War was the Muromachi regime, which broadened the economic base of the warriors, while undercutting the noble proprietors. This trend had started already with the Kamakura "bakufu".