Except for the descendants of Ogedei and Chagadai, most of the royal princes thought that Batu should be elected khan. By this time, however, Batu had decided that he preferred the steppes of the Volga to the steppes of Mongolia. He declined the offer and nominated Mengke, the eldest son of Tului (who had died in 1233), unquestionably one of the most gifted descendants of Chinggis. Mengke's nomination was confirmed by a kuriltai in 1251. He executed several of Ogedei's sons who had opposed his election and quickly restored to Mongol rule the vigor that had been lacking since the death of Chinggis.

Taking seriously the legacy of world conquest, Mengke decided to place primary emphasis on completing the conquest of Asia, particularly China; Europe was to be dealt with later. Because the Song had had the benefit of a lull of nearly ten years in which to recover and to reorganize, conquering Asia had become more difficult than it would have been earlier. Mengke himself took command, but he also placed great responsibility on his younger brother, Khubilai. Another brother, Hulegu, was sent to Iran to renew the expansion of Mongol control in Southwest Asia. Mengke encouraged Batu to raid Central Europe, but did not send him additional resources. Thus, although Batu's armies raided deep into Poland, Lithuania, and Estonia, and again overran Serbia and Bulgaria, these campaigns were not so important as the ones being undertaken in Southeast Asia and Southwest Asia.

Mengke also made some major administrative changes in the khanates established by the will of Chinggis. He disinherited the surviving sons of Ogedei, arranging that he and Khubilai would inherit the lands of East Asia. He also placed a limit on the domains of the successors of Chagadai; these were to end along the Oxus River and the Hindu Kush, instead of extending indefinitely to the southwest. Southwest Asia was to be the inheritance of Mengke's brother, Hulegu, the first of the Ilkhans ("subservient khans") or Mongol rulers of Iran (see The Ilkhans , this ch.).

Mengke prosecuted the war in China with intensity and skill. His principal assistant was Khubilai, who was appointed viceroy in China. In 1252 and 1253, Khubilai conquered Nanchao (modern Yunnan). Tonkin (as northern Vietnam was known) then was invaded and pacified. The conquest ended with the fall of Hanoi in 1257.

Song resistance in southern China was based upon determined defense of its well-fortified, well-provisioned cities. The Chinese empire began to crumble, however, under the impact of a series of brilliant campaigns, personally directed by Mengke between 1257 and 1259. His sudden death from dysentery in August 1259, however, caused another lull in the war with China and put a stop to advances in West Asia.

Data as of June 1989