Was Kublai Khan a Mongol khan or a Chinese emperor?

Both, and that was the tension of his reign. Kublai Khan was a grandson of Genghis who founded the Mongol-led Yuan dynasty of China and proclaimed the name 'Great Yuan' in 1271. He had succeeded his brother Möngke as Khagan in 1260, but he had to defeat his younger brother Ariq Böke in a civil war lasting until 1264, an episode that marked the beginning of the division of the Mongol Empire. As Khagan he still influenced the Ilkhanate and, to a lesser degree, the Golden Horde, but his real power was limited to the Yuan Empire.

In China, Kublai acted like an emperor. Since his early life he had been strongly attracted to Han culture. He made Dadu, modern Beijing, his capital and kept a summer capital at Shangdu, known as Xanadu. By 1279 the Yuan conquest of the Song dynasty was complete, and he became the first non-Han emperor to rule all of China. His court was mixed: thirty Muslims served as high officials, and eight of the dynasty's twelve administrative districts had Muslim governors. In 1260 he created a unified paper currency for his whole domain, which the government accepted in tax payments.

But traditionalists condemned his actions, and critics accused him of being too closely tied to Han Chinese culture. And his empire's overseas ambitions went badly: Vietnam, Burma and Champa became only vassals, and invasions of Japan and Java failed. Two attempts on Japan were partly thwarted by bad weather or by ships built on river boats without keels, and the fleets were destroyed. Costly campaigns and paper money also caused inflation.