Despite the Tatarean theory of the Mongols’ army, the Russian chivalry gathered to the aid of the Polovtisni, and collected an army by the lower Dnieper. Defiantly they killed the ambassadors whom the Mongols sent. The wrathful nomads advanced into the Crimea near the Sea of Azov. The two hosts met in the fatal battle of Kalka. It was the Crécy of Russian chivalry. Hardly a tenth of the army escaped. Ten thousand of the men of Kiev fell; of the princes, six, of the boyars, seventy, died on the field of battle. Matislaf the Bold alone made front, and he was treacherously betrayed and slain. The way into southern Russia was now open; yet, after their victory in 1224, the Mongols disappeared as suddenly as they had come. The hordes had been diverted to complete the conquest of China. For thirteen years they were swallowed up by the steppe. The son of Genghis, “Oktai,” had succeeded the dead conqueror, and had appointed Batui General of the West. Again there was heralded an invasion, this time by one of the outlying tribes of Khirgiz on the eastern border. The blow was aimed at the very heart of Russia. The old Slav ballads, or “_bilinî_,” tell how Oleg the Handsome fell at Riszan. The Tatars entered and burned Moscow in 1237. Onward into the north rolled their conquest, town after town falling. At the Cross of Ignatius, fifty miles from Novgorod, the torrent turned, and, sparing for the time being the ancient republic, swept to the south. Against the cradle of the Russian race, the white-walled many-towered city of Kiev, Mangu, the grandson of Genghis, now marched. By multitudes the Tatars carried the walls. Fighting to the end, the last defenders went down in a ring around the tomb of the great Yaroslav. Russia was prostrate at the feet of the nomads. Her princes became vassals, some to journey as far as the Amur to pay their homage to the Great Khan. Without the Tatar Emperor’s letters-patent, no prince could assume his inheritance. When the envoy presented the documents, the nobles had to prostrate themselves and accept them kneeling. Each Russian city gave its tribute, even the still uninvaded Novgorod. Every peasant in Muscovy paid his poll-tax. Indeed, the supremacy of the czars of Moscow, when the Tatar yoke was at length thrown off, was largely due to the wealth which the Romanov family had managed to acquire and to hold during their term as tax-farmers of the Great Khan. Russian troops, supplied as part of the tribute, engaged in the Tatar wars, getting in one instance of record their share of the booty--after the sack of Daghestan. They were drafted on account of their great size and valor into a body-guard for the Mongol Emperor in Peking, corresponding to the Swiss Guard of Louis XVI.