Mongke Khan (1208–1259) was the fourth Great Khan (Kaghan) of the Mongol Empire. ruling over almost all of Eurasia from 1251 to 1259. Mongke was the son of Genghis Khan's youngest son Tolui, and the brother of Hulegu Khan, Kublai Khan, and Ariq Boke. He was effectively the last ruler of a united Mongol Empire before it splintered into numerous independent Mongol Hordes.
Mongke first appears in the histories as a young man, fighting in the European campaigns from 1236 to 1241. He personally led the attack against the Kypchak and Alan chiefdoms in the Caucasus, and then oversaw the sacking of the Italian ports in the Crimea. Later fighting under the command of his older cousin Batu Khan, he played a major role in the conquest of the Russians, and then took part in the war against Hungary.
Having subdued Hungary, the Mongols were preparing to invade Austria and Germany, but the death of Mongol ruler Ogedei Khan in 1241 forced all the princes of the blood to return to Mongolia to decide the succession.
As expected, Ogedei's son Guyuk was named as successor, but Batu, who favored his favorite cousin Mongke to be Great Khan, delayed his consent, leading to a regency by Ogedei's widow Toregene Khatun.
Toregene's regency proved so tyrannical, however, that Batu finally agreed to let Guyuk ascend as Great Khan in 1246. Guyuk actually proved to be an able Khan, repealing Toregene's draconian edicts and expanding Mongol holdings in China and the Middle East in several successful military campaigns.
But Guyuk was also paranoid that someone would try to overthrow him, and had several senior Mongol leaders seized and executed. Finally in 1248, his suspicion turned to Batu, and he demanded Batu come meet him in Mongolia for consultations, which was widely understood to mean that Batu would be arrested and probably executed. Batu had no choice but to heed the command, but for safety he brought his entire army with him, and civil war seemed inevitable.
But Guyuk died in route to the meeting, which left his widow, Oghul Qaymish, in charge as regent. Batu then outmaneuvered Oghul by joining forces with Mongke's mother Sorghaghtani Beki to call a grand council of all the Mongol leaders in Siberia in 1250, whereat everyone's favorite, Mongke, was duly elected Great Khan.
Shortly thereafter, Oghul came to "pay homage" to Mongke as the new ruler, but she brought the entire army of the Ogedei faction with her, so everyone knew she was planning to attack him. Batu therefore arranged to have Oghul accused of using black magic against Mongke, and she was arrested, sewn up into a sack, and tossed into a river and drowned (which was the traditional Mongol punishment for using black magic).
Mongke was now supreme and uncontested ruler of everything from Siberia and China to the very gates of Europe. Already well known as an able general, he continued to press the Mongol conquests forward, dispatching his brother Helagu to the Middle East (where Helagu extended Mongol holdings all the way to the Red Sea), and personally leading the Mongol armies in a effort to crush the last remnants of the Southern Song Dynasty in China.
Whereas the Song had thus far been able to resist direct assault from their stronghold in Hangzhou, Mongke completely outflanked them by going around them and conquering Yunnan to the west and Vietnam to the south. Completely surrounded, the fate of the Song was sealed. Mongke Khan was killed, however, in one of the sieges of the campaign, leaving his brothers Kublai and Ariq Boke to battle it out for the title of Great Khan in a conflict that would eventually shatter the unity of the Mongol Empire.