Mongol Empire to some extent for murder. Any resistance to Mongol rule was met with massive collective punishment. Cities were destroyed and their inhabitants slaughtered if they defied Mongol orders. Under "Yassa", chiefs and generals were selected based on merit. The empire was governed by a non-democratic, parliamentary-style central assembly, called kurultai, in which the Mongol chiefs met with the great khan to discuss domestic and foreign policies. Kurultais were also convened for the selection of each new great khan. Genghis Khan also created a national seal, encouraged the use of a written alphabet in Mongolia, and exempted teachers, lawyers, and artists
Mongol invasions of Vietnam repeatedly ignored demands to attend the Yuan court and offer his personal submission to the Great Khan. By 1266, a standoff developed, as the Emperor Thánh Tông sought a loose tributary relationship, while Kublai demanded full submission. Trần Thánh Tông sent an official letter requiring Kublai to take his darughachi back. Because of civil war in the Mongol Empire, and the Yuan conquest of Song China, armed conflict was delayed. Instead, Kublai reminded him of the peace treaty signed by the Mongols and Đại Việt. As a result of the Mongol conquest of the Song Empire, by 1278–79, Mongol troops