But the journeys of Chancellor and Jenkinson to the Court of Moscow had more far-reaching effects; the Russians themselves were thereby led to contemplate utilising their proximity to one of the best known routes to the Far East. Shortly after Jenkinson's visit, the Czar, Ivan the Terrible, began extending his dominions eastward, sending at first a number of troops to accompany the Russian merchant Strogonof as far as the Obi in search of sables. Among the troops were a corps of six thousand Cossacks commanded by one named Vassili Yermak, who, finding the Tartars an easy prey, determined at first to set up a new kingdom for himself. In 1579 he was successful in overcoming the Tartars and their chief town Sibir, near Tobolsk; but, finding it difficult to retain his position, determined to return to his allegiance to the Czar on condition of being supported. This was readily granted, and from that time onward the Russians steadily pushed on through to the unknown country of the north of Asia, since named after the little town conquered by Yermak, of which scarcely any traces now remain. As early as 1639 they had reached the Pacific under Kupilof. A force was sent out from Yakutz, on the Lena, in 1643, which reached the Amur, and thus Russians came for the first time in contact with the Chinese, and a new method of reaching Cathay was thus obtained, while geography gained the knowledge of the extent of Northern Asia. For, about the same time (in 1648), the Arctic Ocean was reached on the north shores of Siberia, and a fleet under the Cossack Dishinef sailed from Kolyma and reached as far as the straits known by the name of Behring. It was not, however, till fifty years afterwards, in 1696, that the Russians reached Kamtschatka.