Hist. des Mongols, p. 396.--M.] The Latin world was darkened by this cloud of savage hostility: a Russian fugitive carried the alarm to Sweden; and the remote nations of the Baltic and the ocean trembled at the approach of the Tartars, [28] whom their fear and ignorance were inclined to separate from the human species. Since the invasion of the Arabs in the eighth century, Europe had never been exposed to a similar calamity: and if the disciples of Mahomet would have oppressed her religion and liberty, it might be apprehended that the shepherds of Scythia would extinguish her cities, her arts, and all the institutions of civil society. The Roman pontiff attempted to appease and convert these invincible Pagans by a mission of Franciscan and Dominican friars; but he was astonished by the reply of the khan, that the sons of God and of Zingis were invested with a divine power to subdue or extirpate the nations; and that the pope would be involved in the universal destruction, unless he visited in person, and as a suppliant, the royal horde. The emperor Frederic the Second embraced a more generous mode of defence; and his letters to the kings of France and England, and the princes of Germany, represented the common danger, and urged them to arm their vassals in this just and rational crusade. [29] The Tartars themselves were awed by the fame and valor of the Franks; the town of Newstadt in Austria was bravely defended against them by fifty knights and twenty crossbows; and they raised the siege on the appearance of a German army. After wasting the adjacent kingdoms of Servia, Bosnia, and Bulgaria, Batou slowly retreated from the Danube to the Volga to enjoyed the rewards of victory in the city and palace of Serai, which started at his command from the midst of the desert. [291]