The newly arrived styles immediately evolved into distinctive Japanese traditions, with their own aesthetic principles. The Japanese art world experienced periodic revolutions as new schools of painting in China continued to serve as fresh sources of inspiration. The 15th century marked one of the most important of these revolutions, when the monk-painter Sesshū (1420-1506) and his student Shūgetsu (c. 1427-c. 1510) were allowed to travel as government ambassadors to China, where a century of Mongol invasion had recently come to an end.