Around 1577, Semyon Stroganov and other sons of Anikey Stroganov hired a Cossack leader called Yermak to protect their lands from the attacks of Siberian Khan Kuchum. By 1580 Stroganovs and Yermak came up with the idea of the military expedition to Siberia, in order to fight Kuchum in his own land. In 1581 Yermak began his voyage into the depths of Siberia. After a few victories over the khan's army, Yermak's people defeated the main forces of Kuchum on Irtysh River in a 3-day Battle of Chuvash Cape in 1582. The remains of the khan's army retreated to the steppes, and thus Yermak captured the Siberia Khanate, including its capital Qashliq near modern Tobolsk. Kuchum still was strong and suddenly attacked Yermak in 1585 in the dead of night, killing most of his people. Yermak was wounded and tried to swim across the Wagay River (Irtysh's tributary), but drowned under the weight of his own chain mail. The Cossacks had to withdraw from Siberia completely, but thanks to Yermak's having explored all the main river routes in West Siberia, Russians successfully reclaimed all his conquests just several years later.
Siberian river routes
In the early 17th century the eastward movement of Russians was slowed by the internal problems in the country during the Time of Troubles. However, very soon the exploration and colonization of the huge territories of Siberia was resumed, led mostly by Cossacks hunting for valuable furs and ivory. While Cossacks came from the Southern Urals, another wave of Russians came by the Arctic Ocean. These were Pomors from the Russian North, who already had been making fur trade with Mangazeya in the north of the Western Siberia for quite a long time. In 1607 the settlement of Turukhansk was founded on the northern Yenisey River, near the mouth of Lower Tunguska, and in 1619 Yeniseysky ostrog was founded on the mid-Yenisey at the mouth of the Upper Tunguska.
Between 1620-1624 a group of fur hunters led by Demid Pyanda left Turukhansk and explored some 1,430 miles (2,300 km) of the Lower Tunguska, wintering in the proximity of the Vilyuy and Lena rivers. According to later legendary accounts (folktales collected a century after the fact), Pyanda discovered the Lena River. He allegedly explored some 1,500 miles (2,400 km) of its length, reaching as far as central Yakutia. He returned back up the Lena until it became too rocky and shallow, and portaged to the Angara. In this way, Pyanda may have become the first Russian to meet Yakuts and Buryats. He built new boats and explored some 870 miles (1,400 km) of the Angara, finally reaching Yeniseysk and discovering that the Angara (a Buryat name) and Upper Tunguska (Verkhnyaya Tunguska, as initially known by Russians) are one and the same river.
In 1627 Pyotr Beketov was appointed Yenisey voevoda in Siberia. He successfully carried out the voyage to collect taxes from Zabaykalye Buryats, becoming the first Russian to step in Buryatia. He founded the first Russian settlement there, Rybinsky ostrog. Beketov was sent to the Lena River in 1631, where in 1632 he founded Yakutsk and sent his Cossacks to explore the Aldan and farther down the Lena, to found new fortresses, and to collect taxes.
Yakutsk soon turned into a major starting point for further Russian expeditions eastward, southward and northward. Maksim Perfilyev, who earlier had been one of the founders of Yeniseysk, founded Bratsky ostrog on the Angara in 1631, and in 1638 he became the first Russian to step into Transbaikalia, travelling there from Yakutsk.
In 1643 Kurbat Ivanov led a group of Cossacks from Yakutsk to the south of the Baikal Mountains and discovered Lake Baikal, visiting its Olkhon Island. Later Ivanov made the first chart and description of Baikal.