Rise of Genghis Khan in the context of "Mongol conquest of Khwarezmia"

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.

Tolui (c. 1191 – 1232) was the youngest son of Genghis Khan and Börte. A prominent general during the early Mongol conquests, Tolui was a leading candidate to succeed his father after his death in 1227 and ultimately served as regent of the Mongol Empire until the accession of his brother Ögedei two years later. Tolui's wife was Sorghaghtani Beki; their sons included Möngke and Kublai, the fourth and fifth khans of the empire, and Hulagu, the founder of the Ilkhanate.

Tolui was less active than his elder brothers Jochi, Chagatai, and Ögedei during their father's rise to power, but once he reached adulthood he was considered the finest warrior of the four. He commanded armies under his father during the first invasion of Jin China (1211–1215), and his distinguished service during the Mongol invasion of the Khwarazmian Empire secured his reputation. After the fall of the cities of Transoxiana in 1220, Genghis dispatched Tolui early the following year to subjugate the region of Khorasan, which had begun to cause trouble for the Mongol armies. Tolui executed his orders with ruthless efficiency, assaulting the major cities of Merv, Nishapur, and Herat, and subjugating numerous others. Medieval chroniclers attributed more than three million deaths to the massacres he ordered at Nishapur and Merv; while these figures are considered exaggerated by modern historians, they are evidence of the abnormal brutality of Tolui's campaign.

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.

Hö'elün (Mongolian: ᠥᠭᠡᠯᠦᠨ ᠦᠵᠢᠨ, Ö’elün Üjin, lit. 'Lady Ö’elün'; fl. 1162–1210) was a noblewoman of the Mongol Empire and the mother of Temüjin, better known as Genghis Khan. She played a major role in his rise to power, as described in the Secret History of the Mongols.

Born into the Olkhonud clan of the Onggirat tribe, Hö'elün was originally married to Chiledu, a Merkit aristocrat; she was captured shortly after her wedding by Yesügei, an important member of the Mongols, who abducted her to be his primary wife. She and Yesügei had four sons and one daughter: Temüjin, Qasar, Hachiun, Temüge, and Temülen. After Yesügei was fatally poisoned and the Mongols abandoned her family, Hö'elün shepherded all her children through poverty to adulthood—her resilience and organisational skills have been remarked upon by historians. She continued to play an important role after Temüjin's marriage to Börte—together, the two women managed his camp and provided him with advice.

The Baljuna Covenant was an oath sworn in mid-1203 AD by Temüjin—the khan of the Mongol tribe and the future Genghis Khan—and a small group of companions, subsequently known as the Baljunatu. Temüjin had risen in power in the service of the Kereit khan Toghrul during the late 12th century. In early 1203, Toghrul was convinced by his son Senggum that Temüjin's proposal of a marriage alliance between his and their families was an attempt to usurp their power. After escaping two successive Kereit ambushes, Temüjin was cornered and comprehensively defeated at the Battle of Qalaqaljid Sands.

Temüjin regrouped the scattered remnants of his forces and retreated to Baljuna, an unidentified river or lake in south-eastern Mongolia. There, he and his closest companions swore an oath of mutual fidelity, promising to share hardships and glories. Having spent the summer recruiting warriors attracted by the ideals of his campaign, Temüjin amassed enough of a force to defeat the Kereit in battle that autumn. Three years later in 1206, having defeated all enemies on the steppe, Temüjin entitled himself Genghis Khan at a kurultai and honoured the Baljunatu with the highest distinctions of his new Mongol Empire. Nineteenth-century historians doubted the episode's historicity because of its omission (probably on account of the heterogeneity of the oath-swearers) from the Secret History of the Mongols, a 13th-century epic poem recounting Temüjin's rise.