supported their fellow Cumans in the Caucasus a year before. They fought against the Cuman army near the Ural Mountains, defeating and killing the Khan before making them pay tribute. Following this victory, the Mongols turned east and met Genghis Khan and the rest of the Mongol army in the steppes to the east of the Syr Darya River. Genghis Khan showed great appreciation for his generals' achievements and heaped praise on Jebe and Subutai. Jebe, however, did not survive the campaign long; he died soon afterwards. The importance of the expedition was immense. The expedition was history's longest cavalry raid, with the Mongols riding in three years. Subutai also stationed numerous spies in Rus', who provided frequent reports on what was happening in Europe and Rus'. In 1237 Subutai together with Batu led another attack, and with 120,000 men conquered the Kievan Rus'. References Sources Printed sources Boldur, Alexandru (1992). "Istoria Basarabiei" Editura Victor Frunză, București. Cross, Samuel Hazzard, and Olgerd P. Sherbowitz-Wetzor, trans. (1953). Russian Primary Chronicle. Lavrentian Text Cambridge, MA: Medieval Academy of America. Fennell, John (1983). The Crisis of Medieval Russia 1200–1304. London and New York: Longman. Gabriel, Richard (2004). Subotai The Valiant: Genghis Khan's Greatest General. Praeger Publishers. de Hartog, Leo (1989). Genghis Khan: Conqueror of the World. I.B.Tauris. Jackson, Peter (2005). The Mongols and the West, 1221–1410. Pearson Education Limited. Marshall, Robert (1993). Storm from the East: From Genghis Khan to Khubilai Khan. University of California Press. Martin, Janet (1995). Medieval Russia: 980–1584. Cambridge University Press. Michell, Robert, and Neville Forbes, eds. and trans. (1914). The Chronicle of Novgorod (1914). London: Camden Society. Hugh Munro, Hector (1900). The Rise of the Russian Empire. G. Richards. Wallace, Robert (1967). Rise of Russia. Time-Life Books. Online sources The Chronicle of Novgorod online: http://faculty.washington.edu/dwaugh/rus/texts/MF1914.pdf Further reading Golitsin, N.S., Russian military history, St. Petersburg, 1877, Vol. 4, Part I, pp. 107–09. () Chronicle tales of Tatar-Mongol invasion/Military tales of Ancient Rus, Moscow, 1985, pp. 70–95 () 1223 in Europe Kalka 1223 Conflicts in 1223 Kalka 1223 in the Mongol Empire