Siege of Gurganj in the context of "Jochi"

The Mongol conquest of Persia and Mesopotamia comprised three Mongol campaigns against Islamic states in the Middle East and Central Asia between 1219 and 1258. These campaigns led to the termination of the Khwarazmian Empire, the Nizari Ismaili state, and the Abbasid Caliphate of Baghdad, and the establishment of the Mongol Ilkhanate government in their place in Persia.

Genghis Khan had unified the Mongolic peoples and conquered the Western Xia state in the late 12th and early 13th centuries. After a series of diplomatic provocations on the part of Muhammad II, the ruler of the neighbouring Khwarazmian Empire, the Mongols launched an invasion in 1219. The invaders laid waste to the Transoxianan cities of Bukhara, Samarkand, and Gurganj in turn, before obliterating the region of Khorasan, slaughtering the inhabitants of Herat, Nishapur, and Merv, three of the largest cities in the world. Muhammad died destitute on an island in the Caspian Sea. His son and successor, Jalal al-Din, tried to resist the Mongols, but was defeated and forced into exile. Genghis returned to his campaign against the Jin dynasty in 1223, only retaining governance of the northern Khwarazmian regions.

Between 1219 and 1221, the Mongol forces under Genghis Khan invaded the lands of the Khwarazmian Empire in Central Asia. The campaign, which followed the annexation of the Qara Khitai Khanate, saw widespread devastation and atrocities. The invasion marked the completion of the Mongol conquest of Central Asia, and began the Mongol conquest of Persia.

Both belligerents, although large, had been formed recently: the Khwarazmian dynasty had expanded from their homeland to replace the Seljuk Empire in the late 1100s and early 1200s; nearly simultaneously, Genghis Khan had unified the Mongolic peoples and conquered the Western Xia dynasty. Although relations were initially cordial, Genghis was angered by a series of diplomatic provocations. When a senior Mongol diplomat was executed by Khwarazmshah Muhammed II, the Khan mobilized his forces, estimated to be between 90,000 and 200,000 men, and invaded. The Shah's forces were widely dispersed and probably outnumbered—realizing his disadvantage, he decided to garrison his cities individually to bog the Mongols down. However, through excellent organization and planning, the Mongols were able to isolate and conquer the Transoxianan cities of Bukhara, Samarkand, and Gurganj. Genghis and his youngest son Tolui then laid waste to Khorasan, destroying Herat, Nishapur, and Merv, three of the largest cities in the world. Meanwhile, Muhammed II was forced into flight by the forces of Mongol generals Subutai and Jebe; unable to reach any bastions of support, he died destitute on an island in the Caspian Sea. His son and heir Jalal-al Din managed to mobilize substantial forces, defeating a Mongol general at the Battle of Parwan, but these were crushed by Genghis at the Battle of the Indus a few months later.

Ögedei Khan (also Ögedei Khagan or Ogodei; c. 1186  – 11 December 1241) was the second khan of the Mongol Empire. The third son of Genghis Khan, he continued the expansion of the empire that his father had begun.

Born in c. 1186 AD, Ögedei fought in numerous battles during his father's rise to power. After being granted a large appanage and taking a number of wives, including Töregene, he played a prominent role in the Mongol invasion of the Khwarazmian Empire. When his older brothers Jochi and Chagatai quarrelled over strategies when besieging Gurganj, Genghis appointed Ögedei sole commander; his successful capture of the city in 1221 ensured his military reputation. He was confirmed as heir after further infighting between his elder brothers led to both being excluded from succession plans. Genghis died in 1227, and Ögedei was elected as khan in 1229, after a two-year regency led by his younger brother Tolui.

Chagatai Khan (Mongolian: ᠴᠠᠭᠠᠲᠠᠶ; c. 1184 – 1242) was a son of Genghis Khan, a prominent figure in the early Mongol Empire, and the first khan of the Chagatai Khanate. The second son of Genghis's wife Börte, Chagatai was renowned for his masterful knowledge of Mongol custom and law, which he scrupulously obeyed, and his harsh temperament. Because Genghis felt that he was too inflexible in character, most notably never accepting the legitimacy of his elder brother Jochi, he excluded Chagatai from succession to the Mongol throne. He was nevertheless a key figure in ensuring the stability of the empire after Genghis's death and during the reign of his younger brother Ögedei Khan.

Chagatai held military commands alongside his brothers during the Mongol conquest of the Jin dynasty in 1211 and the invasion of the Khwarazmian Empire in 1219. During the latter, he was appointed to a key role in organising logistics in addition to battlefield responsibilities, but was censured after feuding with Jochi during the Siege of Gurganj. After the campaign, Chagatai was granted large tracts of conquered land in Central Asia, which he ruled until his death. He quarrelled with civil officials such as Mahmud Yalavach over matters of jurisdiction and advised Ögedei on questions of rulership. Chagatai died shortly after Ögedei in 1242; his descendants ruled his territories as the eponymous Chagatai Khanate.