Together with several thousands of people in his retinue, this Kazakh "elected-chief" came to the region where Stroganov family had established dominion in the autumn of the year of 1577. According to the brevet of Stroganov family that they had taken from Tsar Ivan, they were prohibited from receiving the "burglars and fugitives". Despite this prohibition, they kept Yermak under their protection. The main purpose of Yermak and his friends was to taker spoils and to destroy the regions. When Kazakhs learned that it was too easy to pillage and plunder beyond Ural Mountains, they prepared to go to the Sibir regions. They set in motion from the fortified places that had been constructed by Stroganov family members and they surmounted Ural Mountains in the years of 1578, 1579 and 1580. They followed the rivers that reached to Sibir and they arrived to the lands of Sibir and then, they started to destroy and despoil these regions. It has been understood that the Kazakhs were composed of a group of 5.000 people. Most of these people were armed with firearms, in other words, with rifles. However, as the years went by, the number of the Kazakhs decreased.
Yermak captured the city of çimki (or Tyumen) over Tura River in August of the year of 1580. This time, Yermak did not return to the Ural regions in order to spend the winter; and he stayed on the banks of Tura. This region was under the domination of Küçüm Khan. Küçüm Khan decided to fight against Yermak and he started to collect his forces together.
Yermak and his Kazakh people set in motion definitely in the summer of the year of 1581 in order to capture the lands of Küçüm Khan. In order to stop the Kazakh near the village named as Baba Hasar" within the environs of Tavda River, Küçüm Khan sent a big army to this region. The fights lasted for five days. Although the number of the Kazakhs was not ever 2.000 of people, they overwhelmed due to the firearms that they had. These fights of "Baba hasan" that took place on the dates fo 21-26 July determined the destiny of Sibir. Yermak continued his military expedition in the middle of September and he was able to pass from Tobul River to Irtish River. Meanwhile, the Kazaks did only have 545 private soldiers. Küçüm Khan attacked with a significant force in order to defend the little city called as Chuvash" with a distance of 2-3 km from the downstream of Tobul in the east of Irtish river, but he could not achieve any success. Küçüm Khan did also have two artillery pieces; however, his artillerymen did not know how to use them. Therefore, they could not benefit from them.
Upon the defeat of Sibir khan, Ostyak and Vogul people that fought with the khan against the Kazakhs got separated from Küçüm Khan. Then, they went to their homelands. As a result of this situation, the power of Küçüm Khan got gradually decreased and its spiritual influence was undermined. Küçüm who perceived that the situations were going worse in a sensitive manner secretly ran away from the capital city of Isker in the night of 25th/26th October 1581. In the following day, this city was invaded by Kazakhs. The city of Isker or Kışlak was located over a high slope of Irtish River and in a position that could be easily defended. However, Küçüm Khan's soldiers were afraid of the rifles possessed by Kazakhs and therefore, they could not defend the capital city. Upon the capture and settlement of Yermak in the city of Isker, the Ostyak and Tatar people within the environs accepted to pay taxes to him. Therefore, the elected-chief of the vagrant Kazakh gangs was nearly promoted to the degree of a sovereign.