Kazakh Khanate reached its greatest power in the first quarter of the XVI century, especially under the rule of Kasym Khan (1512 - 1521 years). In fact, he started to govern while Burunduk was still a Khan.
Name of sultan Kasym was mentioned for the first time in the sources in connection with the description of the wars of Muhammad Shaybani with Kazakh rulers back in the 80's of the XV century, where it is spoken about him as one "of the famous sultans and glorious Bahadur" of Kipchak and leaders of cavalry troops of Burunduk Khan.
The rivalry of the two most powerful men in Khanate ended with the victory of vigorous sultan Kasym. Not earlier than in autumn 1511, Burunduk Khan went with a bunch of close people to Maverannahr. The supreme power in the Khanate passed to the descendants of Janibek.
In 1509 - 1510 years, Muhammad Shaybani made several trips to the territory of the Kazakhs. The result of these campaigns was his ability to temporarily displace the Kazakh rulers outside the oases of Turkestan.
In 1510, Muhammad Shaibani again came to Sygnak, but suffered a crushing defeat of the troops of the sultan Kasym; the remains of Uzbeks escaped to Samarkand. At the end of that year, Muhammad Shaybani died in Khorasan under the Merv, in a battle with the Shah of Iran.
Kasym Khan did not fail to take advantage of these circumstances to consolidate his power in southern Kazakhstan. Soon, under the authority of the Kazakh Khan passed the most southern city of Syr Darya, Sairam.
In the second decade of the XVI century, Kasym Khan finally asserted his dominance over the vast expanses of the Kazakh steppe territory. At this time, the south boundaries of the Khanate went out on the right bank of the Syr Darya and included part of the cities of Turkestan, in the south-east they covered most of the foothills and valleys of Zhetysu, in the north and north-east went through the Ulutau mountains and Balkhash lake, reaching spurs of the Karkaraly mountains, in the north-west reached the basin of Yaik river.
Kazakh Khanate was gradually drawn into the international relations of that time. One of the first countries that joined the diplomatic relations with the Kazakh Khanate was Moskow state that was the reign of Grand Prince Vasily III (1505 - 1533 years). The history of the Kazakh Khanate under the reign of Kasym Khan is also notable for the fact that in those years the Kazakhs became known as an independent ethnic group in Western Europe: Austrian diplomat Sigismund Gerberstein wrote about the Kazakhs in his records, he visited Moscow several times (in 1517 and 1526 years).
According to the sources, the population of the Kazakh Khanate under Kasym Khan reached 1 million. Kazakh folk tradition associates with the name of Kasym creation of laws known as "Kasym Khannyn Kaska Joly".
Despite the significant consolidation, the Kazakh Khanate under Kasym Khan was not, however, a centralized state. It showed up immediately after his death, when separatism of sultans is manifested and strife began. The negative effects of civil wars on the position of the Khanate particularly sharply affected the unfavorable foreign environment. Moghul and Uzbek khans created an alliance against the rulers of the Kazakh Khanate.
According to Mouhamadou Haidar, after the death of Kasym Khan his son Mamash (1521-1522 years) established himself on the throne. Takhir Khan ruled in about 1523/24- 1531/32 years.
Takhir Khan was so influential like his uncle Kasim. He was distinguished by extreme cruelty and had neither diplomatic nor military talents, as evidenced by his repeated military defeats and diplomatic failures. External and domestic policy adopted by Khan was detrimental to the fate of the Khanate and Takhir himself. After the rise of the Kazakh Khanate came years of disaster and confusion.
Almost until the end of the XVI century, towns near Syr Darya, Sygnakm Sauranm Otyrar, and Turkestan (Yasi city was called so from the XVI century) and others were part of the state of Shaybanids of Maverannahr.
By the second half of the XVI century, Kazakh Khanate experienced strong attenuation due to the endless wars, civil strife, but under the reign of Hak-Nazar Khan, it reached a certain rise in the domestic and foreign political life. Entering the imperial throne, Hak-Nazar Khan (1538 - 1580 years) battled Oirats and Abdur-Rashid Khan of Mogulistan, and had stood for the time the Kazakh lands to the east and south of Zhetysu. Tenacious struggle began in Mogulistan in 1560. In the middle of the XVI century, Kazakhs occupied not only the middle reaches of Syr Darya River, but also the nomadic territories of Mogulistan. The desire ofAbd ar-Rashid Khan to oust Kazakhs from Mogulistan was the cause of the struggle. Under the rule of Hak-Nazar Khan, Kazakh-Mogul relations were tense and often Mogul khans got the advantage in this fight.
After accession of Kazan city to Russia in 1552 and Astrakhan in 1556 - under the authority of the Russian state moved the whole basin of the Volga. During the XVI century, Bashkirs, the Siberian Khanate were attached to the Russia. The consequence of this was that the Nogai Horde retreated to the south and east. In the second half of the XVI and XVII centuries, their nomadic territories stretched from the Volga to the Irtysh. Bashkirs and Siberian Tatars also pushed them into the Kazakh steppes. During the second half of XVI century, Karakalpaks appeared in Central Kazakhstan and in the lower reaches of the Syr Darya.
In the middle of the XVI century, Hak-Nazar Khan managed to take control of the land from the Syr Darya to the Aral Sea and along the left bank of Emba and Yaik, taking under his own power part of the Nogay uluses.
In folk tales name of Hak-Nazar Khan is surrounded with glory. Memory of him was not safed only by Kazakhs themselves, which include the formation of three Kazakh jüzs to the time of his reign, but even by Bashkirs and Nogays.
After the death of Hak-Nazar Khan, Shigay became a khan; he was the son of Zhadik Sultan, grandson of Janinek Khan. Shigay and his sons took an active part in the fight of Shaybanid Abdallah Khan against Nauruz-Ahmad Khan and his sons. For substantial assistance provided by Shigay Khan in this fight, Abdallah Khan, in June 1581, awarded Shigay with Khujand in inheritance. For the last time name of Shigay Khan is mentioned in 1582 according to the sources. He died at the age of about 80 years. He was buried in the village Kumushkent, near Bukhara.
Tauekel Khan ruled after Shigay Khan. Exact starting year of his reign is not defined in sources. Being very energetic, ambitious and enterprising, Tauekel could not nourish hopes of becoming an independent ruler of his people, while remaining under the patronage of Abdallah. On the other hand, with the completion of a victorious war with the Sultan Baba a common goal did not exist: the surrounding areas to the nomadic territories of Kazakhs finally recognized the authority of Bukhara, and with it, disappeared the need to support the Kazakh rulers, whom Abdullah regarded only as useful allies. Kazakhs, in turn, has long sought to acquire Turkestan cities and Tashkent, and only seen Abdallah not as a patron but a rival.
Abdullah Khan died in 1598 and in the summer of that year, his son Abd al-Mumin was killed by a rebel emirs, and in the realm of Shaybanids came troubled times. Monarchy of Abdallah finally was falling apart. At different ends of the former vast state - in Bukhara, Herat, Balkh and Khiva - different independent sovereigns cane out. Tauekel Khan used this piece of sharp political crisis for his re-invasion in the Shaybanid’s state.
In a short time, he mastered Sairam, Tashkent, Turkestan, Samarkand and went with the army in the direction of Bukhara. However, the movement of Kazakhs to the deep oases of Central Asia has been suspended under the walls of Bukhara.
In one of the next battles, Tauekel Khan was seriously wounded, went to Tashkent and died there in 1598. After some time, peace was achieved: Kazakhs refused to have Samarkand, but retained Tashkent, Sairam, and Turkestan.