The enfeeblement of the Golden Horde seemed to the Lit’uanian Grand Duke a favourable opportunity to extend his influence in the Tartar steppes and constitute himself the heir of the dying sovereignty. Concluding for the moment a perpetual peace with the Order, against whom he had scarcely ceased to fight since his accession to the Grand Duchy, he mustered a formidable army to support him in this mighty enterprise. Poles, Lit’uanians, and Russians marched under his banner against the Tartars, and Konrad von Jungingen, as a guarantee of good faith, sent five hundred of his knights to do battle against the infidels. [Sidenote: 1399] On the banks of the Vorskla (a tributary of the Dniepr), Vitovt came in contact with the lieutenant of Timur and suffered a disastrous overthrow, losing two-thirds of his army and seriously damaging his military reputation. Notwithstanding this victory the new master of the Horde, Koutluk Khan, had his power disputed by more than one competitor, and Vasili took advantage of this fact to discontinue payment of the annual tribute. [Sidenote: 1408] The temerity of his action, overlooked for many years, brought on him at last the chastisement of the Mongols, who, under the leadership of Ediger, the victor of the Vorskla, made a sudden inroad upon Russian territory. Vasili imitated the tactics of his father on a similar occasion; leaving Moskva with a strong garrison to defend the Kreml, he betook himself to the northern districts of his realm to raise what forces he might against the invaders. The assault on Moskva was weakened by the want of siege engines (cannon were just beginning to be used by the Russians and Lit’uanians), and Ivan Mikhailovitch, Prince of Tver, was summoned to support the Khan with his artillery. For once hereditary hatred gave way to patriotic instincts, and Ivan withheld the demanded assistance. The troops of Ediger ravaged and burnt far and wide over the Russian plain, and sacked many a town and village in the Grand Principality, but they could neither force Vasili into a combat nor make an impression on the walls and towers of the Kreml. A threatened revolution at the Horde made the Khan anxious to retreat, and his offer of withdrawal on receipt of a war levy was gladly accepted by the Moskovites, who were dreading a famine; 3000 roubles purchased the departure of the Mongol army, and the Velikie Kniaz was able to return to his rejoicing capital.