The Mongol Empire emerged from the unification of several nomadic tribes in the Mongol homeland under the leadership of Genghis Khan (c. 1162 - 1227), whom a council proclaimed ruler of all the Mongols in 1206. The empire grew rapidly under his rule and that of his descendants, who sent out invading armies in every direction. The vast transcontinental empire connected the East with the West in an enforced Pax Mongolica, allowing the dissemination and exchange of trade, technologies, commodities and ideologies across Eurasia.
The empire began to split due to wars over succession, as the grandchildren of Genghis Khan disputed whether the royal line should follow from his son and initial heir Ögedei or from one of his other sons, such as Tolui, Chagatai, or Jochi. The Toluids prevailed after a bloody purge of Ögedeid and Chagataid factions, but disputes continued among the descendants of Tolui. A key reason for the split was the dispute over whether the Mongol Empire would become a sedentary, cosmopolitan empire, or would stay true to the Mongol nomadic and steppe-based lifestyle. After Möngke Khan died (1259), rival kurultai councils simultaneously elected different successors, the brothers Ariq Böke and Kublai Khan, who fought each other in the Toluid Civil War (1260–1264) and also dealt with challenges from the descendants of other sons of Genghis. Kublai successfully took power, but civil war ensued as he sought unsuccessfully to regain control of the Chagatayid and Ögedeid families.
During the reigns of Genghis and Ögedei, the Mongols suffered the occasional defeat when a less skilled general received a command. The Siberian Tumeds defeated the Mongol forces under Borokhula around 1215–1217; Jalal al-Din defeated Shigi-Qutugu at the Battle of Parwan in 1221; and the Jin generals Heda and Pu'a defeated Dolqolqu in 1230. In each case, the Mongols returned shortly after with a much larger army led by one of their best generals, and were invariably victorious. The Battle of Ain Jalut in Galilee in 1260 marked the first time that the Mongols would not return to immediately avenge a defeat, due to a combination of the death of Möngke Khan in 1259, the Toluid Civil War between Ariq Böke and Kublai Khan, and Berke Khan of the Golden Horde attacking Hulegu in Persia. Although the Mongols launched many more invasions of the Levant, briefly occupying it and raiding as far as Gaza after a decisive victory at the Battle of Wadi al-Khaznadar in 1299, they withdrew due to various geopolitical factors.
In 1304 the three western khanates briefly accepted the nominal suzerainty of the Yuan dynasty,but in 1368 the Han ChineseMing dynasty took over the Mongol capital. The Genghisid rulers of the Yuan retreated to the Mongolian homeland and continued to rule there as the Northern Yuan dynasty. The Ilkhanate disintegrated in the period 1335–1353. The Golden Horde had broken into competing khanates by the end of the 15th century whilst the Chagatai Khanate lasted in one form or another until 1687.
What is referred to in English as the Mongol Empire was called the Ikh Mongol Uls (ikh: "great", uls: "state"; Great Mongolian State). In the 1240s, one of Genghis's descendants, Güyük Khan, wrote a letter to Pope Innocent IV which used the preamble "Dalai (great/oceanic) Khagan of the great Mongolian state (ulus)".
After the succession war between Kublai Khan and his brother Ariq Böke, ape limited Kublai's power to the eastern part of the empire. Kublai officially issued an imperial edict on 18 December 1271 to name the country Great Yuan (Dai Yuan, or Dai Ön Ulus) to establish the Yuan dynasty. Some sources state that the full Mongolian name was Dai Ön Yehe Monggul Ulus.