The Mongol Empire
The steppe and nomadic power, Temujin's rise and the 1206 proclamation, the army and the yam relay system, conquests of north China, Central Asia, Persia, Russia and the sack of Baghdad, Ain Jalut, the four khanates, the Pax Mongolica and Eurasian exchange, the Black Death, and the Mongol legacy in Russia, Iran, China and India (the Mughals).
From the steppe to most of Eurasia
At its peak the Mongol empire was the largest contiguous land empire in history. Its yam relay system of horse stations carried messages and officials across Eurasia; its tolerance of many religions and recruitment of administrators from conquered peoples made it a channel for ideas, technologies and goods. The cost was immense: contemporary sources describe the destruction of cities such as Merv and Baghdad, and population losses in China and Iran were severe. The Mughal emperors of India descended from Chinggis Khan and Timur.
David Morgan, The Mongols (2nd ed., 2007); Peter Jackson, The Mongols and the Islamic World (2017); Jack Weatherford, Genghis Khan and the Making of the Modern World (2004), a sympathetic account; The Secret History of the Mongols (13th century).