Bayan (1236-1295) was the most trusted general of Kublai Khan and the supreme commander of the Yuan army in the final campaign against the Southern Song. He came from the Baarin, one of the Mongol tribes, and grew up in the western part of the Mongol Empire, in Persia (today's Iran region). When he came east as an envoy, Kublai was so struck by his calm judgment that he kept him at his side, and Bayan rose to lead the greatest army of his age.
In 1274 Kublai gave Bayan command of the huge army that would finish the war against the Song. Kublai told him to remember Cao Bin, a general of long ago who had captured a great city without killing its people. Bayan kept that order in mind: at Dingjiazhou in 1275 he crushed the last main Song army on the Yangtze, and in 1276 he entered the Song capital Lin'an, one of the largest cities in the world, without letting his soldiers destroy it.
Records describe Bayan as a man of few words whose plans were deep and whose armies moved like water finding its way. The Song people, who had feared a terrible sack, remembered that the city's markets opened again within days of the surrender. After the war Bayan served the Yuan court as its leading statesman and soldier until his death in 1295, and later generations counted him among the greatest generals of the Mongol Empire.