With the annexation of the khanates of Kazan and Astrakhan in the 1550s, and the formal submission of the Bashkir tribes in the second half of the sixteenth century, large populations of non-Slavic and non-Christian populations found themselves under Russian rule. Already before the annexations of the Kazan and Astrakhan khanates there were substantial Finno-Ugric and Muslim populations residing in Muscovy. As early as the eleventh century the Russian principalities of Vladimir and Suzdal' were established on territories that several Finno-Ugric peoples inhabited, the Merya, Muroma and Meshchera. By the sixteenth century the latter groups had become russified, but as Russia gained control of territories in the Oka and Middle Volga regions other Finno-Ugric and Turkic groups became Russian subjects, but were not russified, retaining separate cultural and linguistic identities. As early as the end of the fourteenth century Turkic Muslims also formed part of the Muscovite state, and Muslims were among the troops of Ivan IV in the conquest of Kazan. These were so-called ‘service Tatars’, who included the khans of Kasimov and Muslim communities inhabiting the Oka Valley. Similarly, even before the 1550s, the Muscovite nobility and especially servitor class reflected a similar multi-ethnic character. In general terms cooperation and mutual accommodation characterized the relations between the Russian authorities and the native inhabitants, and particularly the elites, of the Volga-Ural region between 1600 and 1850.