Back in 1717 some leaders of the Kazakhs, given the real threat from external enemies, turned to Peter I with a request for citizenship. The emperor at the time decided not to intervene in "Kazakh affairs." Later along the Kazakh lands was established line of military fortifications, which subsequently became the cities: Omsk (1716), Semipalatinsk (1718), Ust-Kamenogorsk (1720), Orsk (1735). Traditionally, for the protection of the newly organized boundary line drawn Cossacks organized Siberian Cossacks.
At the beginning of the XVIII century, the Kazakh Khanate was a politically fragmented country. Kazakh tribes were merged into three education - zhuzes: Senior, Intermediate and Junior.
To the east, menace is Dzungar Khanate. From the South Kazakh Khanate of Khiva and Bukhara threatened. Heavy political situation inside the Khanate and the continuing internal conflicts, considerably weakened the Kazakh Khanate. In 1723 Jungar tribes once again attacked the loose and scattered Kazakh zhuzes. This year has gone down in history of the Kazakhs as "the great tribulation."
In 1730, the Little Horde Khan Abul Khair called on the Russian government to the military alliance. It was rejected and instead invited to patronage (protectorate) Russia. February 19, 1731 Empress Anna signed the instrument of voluntary joining the Little Horde in the Russian Empire. October 10, 1731 and most of the elders Abulhair Little Horde entered into an agreement and took the oath on the inviolability of the contract.
Although in those days Average Horde, which was headed by Abulmambet was much less connected with Russia, and Senior Juz was ruled Jungars and Kokand Khan, Khan Abulhair separate agreement marked the beginning of a constantly increasing Russia's influence on the life of Kazakhs. In 1740 Middle Horde came under the patronage (protectorate). In 1741-1742 Jungar forces again invaded the Middle and Junior zhuzes, but the intervention of Russian border authorities forced them to retreat. Ablay was captured by dzhungar, but a year later was released under the mediation of the Orenburg governor II Neplueff and Abulmambet (prisoner Abylaja instead he sent his son Abul Feyziyev). Abylay in those days was just beginning his political career. Abulmambet repeatedly offered ABYLAI become instead Khan. Abylay but refused, saying that Khan will be after him (Abulmambet) death. As a result of the weakening power of the Kazakh khans and the remoteness of new regions of Russia, part of the lands of the Middle Horde, formally passed under the protection of Russia, as well as land Senior Juz in the late XVIII fell under the rule of the Kokand khans.
In 1787 part of the Kazakh tribes Little Horde, which is closely Khivans, were allowed to roam the Urals and the Volga. This decision formalized its Emperor Paul I in 1801, when the 7500 Kazakh families was formed allegiance Bukeyev (Internal) Horde led by Sultan Boquete.
In 1818, several genera Senior Juz announced the introduction under the protection of Russia. Over the next 30 years, where under pressure, where most births voluntarily Senior Juz announced the adoption of Russian citizenship [4] [5]. In 1822, Tsar Alexander I issued a decree on the introduction of the developed MM Sperdnski "Charter on the Siberian Kirghiz", which eliminated khan power in Kazakh zhuzah (except Bukeyev hordes where Khanate was abolished by Nicholas I in 1845). Despite this, Russia has long ruled Kazakh zhuzami through the College of Foreign Affairs, representatives of the Kazakh zhuzes arriving in Russia, was called Ambassadors.
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Среднеазиатские владения Российской империи — Википедия
You may find it strange, but many nations joined the Russian Empire voluntarily. Moreover, they waited for decades until the Czar agrees to take them into the Empire.