Ogedei (1185 – 1241) was Genghis Khan’s third son and unexpected successor. His two older brothers, Jochi and Chagatai, were ahead of him in the line of succession but had developed a bitter enmity. Jochi claimed the right to inherit as eldest, but Chagatai countered that Jochi, whose parentage was questionable because their mother had been kidnapped by an enemy of Genghis in the year before Jochi’s birth, was a bastard, making Chagatai the eldest trueborn son. When it became clear that the empire would descend into civil war if either inherited, Ogedei was selected as a compromise heir.
Realizing that he was not Genghis’ military equal, Ogedei was open to wise counsel and, relying on capable subordinates, greatly expanded the frontiers of the Mongol Empire to its greatest southward and westward extents. From his capital in Mongolia, he directed simultaneous campaigns on multiple fronts separated by thousands of miles, relying on field generals acting independently within their theaters, but subject to Ogedei’s orders, relayed via a swift horse relay courier network.
In the east, the Mongols continued the campaign against the Jin, in alliance with the Song Dynasty in southern China. Ogedei commanded in person until 1232, then returned to Mongolia, entrusting to subordinates the final mopping-up operations, which terminated with the extinguishment of the Jin Dynasty in 1234. The Mongols then fell out with their Song allies, and a new campaign began against southern China. Simultaneously, Ogedei’s Mongols invaded the Korean Peninsula and asserted Mongol suzerainty.
In the south, Ogedei’s armies invaded India, marching into the Indus Valley and on to the Delhi Sultanate, occupying parts of today’s Pakistan and Punjab. Simultaneously, another Mongol army marched into and subdued Kashmir.
In the west, Ogedei’s armies marched out of the recently conquered Khwarezm to subdue the remainder of today’s Central Asia, overrunning Khorasan, Afghanistan, Persia, and reaching Mesopotamia. From there, they turned northward and conquered Armenia, Georgia, and the Caucasus region then continued to reduce Russia to centuries of vassalage. Afterward, they penetrated into Eastern Europe, capturing Poland, Bulgaria, Hungary, and reaching the Adriatic Sea. The Mongol forces in Europe under Subutai were drawing plans to continue the advance into Italy and Central Europe, when news arrived of Ogedei’s death, which necessitated a halt to the campaign and a return to Mongolia for the selection of a new Khan.