In 1579, Yermak began the second plundering expedition, which in two years resulted in the capture of the Tatar kingdom. When the conquerors entered Sibir they had been reduced from over 800 to about 400 men. But this handful represented the power of the Tsars and Yermak could sue for pardon, with the offer of a kingdom as his ransom. Before the close of the Sixteenth Century the land had been finally subdued. Sibir itself, which stood on a high bluff on the right bank of the Irtish, exists no more, having probably been swept away by the erosions of the stream. But ten miles farther down another capital, Tobolsk, arose, also on the right bank, and the whole of the north was gradually added to the Tsar's dominions. The fur trappers, more even than the soldiers, were the real conquerors of Siberia. Nevertheless, many battles had to be fought down to the middle of the Seventeenth Century. The Buriats of the Angora basin, the Koriaks, and other tribes long held out; but most of the land was peacefully acquired, and permanently secured by the forts erected by the Cossacks at the junction of the rivers, at the entrance of the mountain passes, and other strategic points. History records no other instance of such a vast dominion so rapidly acquired, and with such slender means, by a handful of men acting mostly on their own impulse, without chiefs or instructions from the centre of authority. Even China allowed the Cossacks to settle on the banks of the Amur, though the treaty of Nerchinsk required the Russians to withdraw from that basin in 1689. But during the present century they have been again attracted to this region, and the Government of St. Petersburg is now fully alive to the advantages of a free access by a large navigable stream to the Pacific seaboard. Hence, in 1851, Muraviov established the factory of Nikolaievsk, near the mouth of the Amur, and those of Mariinsk and Alexandrovsk at either end of the portage connecting that river with the Bay of Castries. During the Crimean war its left bank was definitely secured by a line of fortified posts, and in 1859 a ukase confirmed the possession of a territory torn from China in time of peace. Lastly, in 1860, while the Anglo-French forces were entering Pekin, Russia obtained without a blow the cession of the region south of the Amur and east of the Ussuri, stretching along the coast to the Corean frontier.