Möngke Khan (1208-1259, also transliterated as Mongke, Mongka, Möngka, Mangu) was the fourth khan of the Mongol Empire. He was the son of Tolui, brother of Hulegu, and a grandson of Genghis Khan. He was the khan of the Mongol Empire from 1251 to 1259.
Möngke is noted as participating in the European campaign of 1236-1242, participating in the campaign against the steppe peoples to the southeast of the Russian principalities, the destruction of Kiev, and the assault of Hungary. In the summer of 1241, before the premature end of the campaign, Möngke returned home.
After the death of the third khan, Güyük, Möngke found himself the champion of the factions of Genghis' descendants who aimed to supplant the branch of Ögedei. Batu, the senior male of the family, had almost come to open warfare with Güyük in 1248, the khan's early death precluding this. Batu joined forces with Tolui's widow to outmaneuver the regent, Ögedei's widow Oghul Ghaimish. Batu called a kuriltai in Siberia in 1250, which was protested as not being in Mongolia proper. However, Batu ignored the opposition, had his brother Berke call a kuriltai within Mongolia, and elected Möngke khan in 1251.
Realizing they had been outmaneuvered, the Ögedeiid faction attempted to overthrow Möngke under the pretext of paying him homage, but their conspiracy was clumsy and easily avoided. Oghul Ghaimish was sewn up into a sack and drowned.
Möngke, as khan, seemed to take much more seriously the legacy of world conquest he had inherited than did Güyük. He concerned himself more with the war in China, outflanking the Song Dynasty through the conquest of Yunnan in 1254 and an invasion of Indochina, which allowed the Mongols to invade from north, west, and south. Taking command personally late in the decade, he captured many of the fortified cities along the northern front. These actions ultimately rendered the conquest a matter of time. He dispatched his brother Hülegü to the southwest, and act which was to expand the Mongol Empire to the gates of Egypt. European conquest was neglected due to the primacy of the other two theaters, but Möngke's friendliness with Batu ensured the unity of empire.
However, while conducting the war in China, Möngke fell ill of dysentery and died (in 1259), which aborted Hülegü's campaign, staved off defeat for the Song, and caused a civil war that destroyed the unity, and invincibility, of the Mongol Empire.