The Mongol Yuan dynasty unsuccessful invaded Dai Viet in 1250s and 1280s, though they sacked Hanoi. The Ming dynasty of China conquered Dai Viet in 1406, brought the Vietnamese under Chinese rule for 20 years, before they were driven out by Vietnamese leader Lê Lợi. The Chinese brought several thousands of Vietnamese artisans, skilled workers to China, resettled them in Beijing. During the 15th century, Dai Viet's population skyrocketed from 1.9 million to 4.4 million. The fourth grandson of Lê Lợi, king Lê Thánh Tông (r. 1460–1497), is considered one of the greatest monarchs in Vietnamese history. His reign is recognized for the extensive administrative, military, education, and fiscal reforms he instituted, and a cultural revolution that replaced the old traditional aristocracy with a generation of literati scholars, adopted Confucianism, and transformed a Dai Viet from a Southeast Asian style polity to an bureaucratic state, and flourished. Thánh Tông's forces, armed with gunpowder, overwhelmed the long-term rival Champa in 1471, occupied the Laotian and Lan Na kingdoms in 1480s.