One of the decisions of the Mongols kurultai of 1228 was to launch a campaign against the Bulgars of the Middle Volga. A year later, Batu reached the shores of Iaik (Ural), where he was successful in defeating the Bulgar outpost detachments. Despite this victory, he chose to interrupt the campaign, only to renew it in 1232, at which time he failed to bring the Bulgar lands under Mongol control.
The outcome of these military operations prompted the kurultai of 1235 to decide on a general campaign aimed at conquering not merely the Bulgar territories but the entirety of Batu's ulus. In the spring of 1236, after careful preparations, Batu's 150,000-man army set forth for the Eastern European campaign. His forces were joined by those of other Ginghisids (some 450,000 men), whose participation in the campaign had been made mandatory by the kurultai. 
Earlier encounters with the Mongols had awakened the Bulgars to the reality of the restless giant to the east. In response, they had improved the defense of their cities to the degree that Bulgar alone boasted a defense force of 50,000 men. The Bulgars, however, were no match for Batu's formidable army, which in 1236, conquered and devastated their lands. The charred buildings and bones unearthed by archaeologists in 1969 and 1970 on the territory of the former Bulgar state have provided time-capsule evidence of the magnitude of the destruction. 
After conquering the Bulgar lands, Batu's armies swept through Russia west of Moscow and, in the winter of 1240, reached Kiev, the seat of the grand prince and the Metropolitan See of Rus'. On December 6, abandoned by its grand prince, Michael of Chernigov, Kiev fell. Batu's armies continued their victorious march through Eastern Europe. The northern army moved forward through Podolia, Volynia, Galicia, Central Poland, Moravia, and Silesia; the southern army, through the central and southern Carpathians to Hungary, where they defeated King Bela IV on April 11, 1241.
The Hungarian plains, with their excellent grazing ground, prompted Batu to begin to settle down and even mint coins there. As soon as the news of the great khan's death on December 11, 1241, reached him, however, Batu abandoned his Hungarian conquests, pushed through the Danubian plains into the steppes on the northern shore of the Black Sea, and moved north along the Volga to Bulgar, where he could observe more closely the issue of the succession to the great khan. 
At the same time, he embarked on the task of organizing the conquered lands and setting up the blueprints of his rule over the sociopolitical entity that came to be known as Orduyu Muazzam (Great Horde) or the Golden Horde. Batu chose Bulgar as his temporary capital. There the first coins of the Golden Horde were minted and vassal rulers of the conquered lands came to receive their yarlyks (charters).  Batu built himself a new capital, Saray, on the lower Volga, and as soon as it was completed, he moved there and the political center of the Golden Horde shifted to the south.
The immediate impact of Batu's conquest of the Bulgar state was massive population dislocation. Most of the survivors moved north, to the lands beyond the Kama. Some made their homes on the shores of Kazanka, a tributary of the Volga; others, in the Moksha river basin or along the Ika and Belaia rivers; still others went to the Bashkir lands.  Some, however, chose to settle among the Udmurts, thus contributing to what Khalikov calls «the Bulgarization and Islamization of the local Turkic tribes.» Khalikov also claims that in settling on the lands to the north, the Bulgars were returning to the homeland of their ancestors, thus making possible the preservation of their anthropological purity. 
The demographic shift to the north, northeast, and northwest was partly responsible for the emergence of new cities that developed as economic centers rather than military outposts and fortifications. By the end of the thirteenth and the beginning of the fourteenth centuries, these urban centers had become the nuclei around which the principalities of Kazan, Shongut, Narovchat, Zhukotin (Zhuketau), and Kashan emerged; in addition, Bulgar revived.  Of the principalities that emerged in the Kazanka river basin, the rulers (emirs) of the Kazan principality (Table 1) belonged to the former Bulgar dynasty, a fact attested to by the epitaph dated September 27, 1297, on the tombstone of Princess Altyn Berke, the niece of Emir Mahmud. 
TABLE 1 RULERS OF THE PRINCIPALITY OF KAZAN (1297 – 1437)
Ali (Gali) Bek
1429 – 1445
NOTE: Based on the documents that I have consulted, I have compiled this table. Where years are supplied, the number has been mentioned in the document.
Not all the inhabitants of the Bulgar state moved north after the destruction of their homes. Many stayed and even chose to revolt against their alien conquerors. Batu Khan sent one of his fiercest commanders, Subudai, to quell a revolt led by Jiku and Baian in 1238 and 1239, and Mengu Temir himself went to the Middle Volga to put down a revolt of the local population in 1261. 
Soon, however, as the political and administrative structure of the Golden Horde took shape and the people of the former Bulgar state began rebuilding their lives in the new principalities that had emerged as the result of the fragmentation that followed the Mongol conquest, revolts became the exception rather than the rule. There may have been two major reasons for this acceptance. First, despite their vassal status, and although their emirs could not rule without receiving a yarlyk from the khan in Saray, the Bulgars enjoyed a considerable degree of autonomy, which at times even enabled them to exhibit a certain independence in foreign policy.  Second, after the adoption of Islam by Khan Berke (1256 – 1266) – and even more so under Khan Ozbek (1313 – 1341), who made Islam the official religion of the Golden Horde – the Bulgars may have acquired a sense of belonging to the political entity, which they probably perceived as an Islamic commonwealth.
The khans of the Golden Horde (Table 2) never aimed at molding the conquered lands in accordance with a Mongol Weltanschauung. The goals of their administration were of a more pragmatic nature: They sought efficient support of the complex state bureaucracy and the army through taxes and replacement of military losses. It would be erroneous, however, to regard the Golden Horde as merely a steppe empire and ignore its unique nature, which combined in one sociopolitical entity the characteristics of the nomadic as well as settled societies over which the Mongol khans were beginning to rule. There were at least 25 major cities in the Golden Horde. Saray, its capital, was not a tent city. By the time of Khan Ozbek's rule, it had grown into a sophisticated urban entity with a complex water supply system and a physiognomy that was distinctly Eastern and was shaped by the mosques, medreses (Muslim schools of higher learning), caravanserais, and baths. Furthermore, the architecture of Saray was not a pale copy of Bulgar architecture but had a character of its own. 
The ethnic and cultural diversity, the differences in the socioeconomic development, and the political and administrative practices that Batu and his successors encountered in the Golden Horde determined their approach to the conquered lands and shaped their administration. For the Bulgar lands, for instance, Mongol administration amounted to indirect rule. In the southwest, the Mongols displaced the Russian princes and ruled directly; in the northeast, they retained the local hierarchy and princes, who became the intermediary (but crucial) links responsible for the implementation of the economic and administrative policies of the khan.  However, a system of tax collection and drafting of military recruits, which emerged as the backbone of Mongol administration, was applied throughout.
To assess the potential tax and recruit contributions of the population and also ensure the efficient collection of the taxes, Berke Khan ordered a series of population censuses between 1251 and 1262 and appointed tax officials who were responsible for supervision of tax collection and recruitment of soldiers. Although there are no specific data regarding the Bulgar lands, it can be assumed that their census took place between 1253 and 1257, because it was at this time that the Iranian territories and the lands of the western ulus were being registered in census reports. 
In keeping with the tradition of the Mongol-Turkic states, the Golden Horde deemed the collection of taxes and duties its main administrative function.  Consequently, Batu's ulus was divided into distinct administrative units. The Russian lands, the Caucasus, and the northern Black Sea shore were divided into several smaller administrative units, and the principalities that were emerging in the Middle Volga were organized as the Bashkir (or Bulgar or Moksha) ulus.
In addition to taxes to the local emirs and feudal lords, the population of the former Bulgar state was subject to a series of duties, obligations, and taxes that were paid to the Golden Horde khan; these included tithe, storage tax, road and river tax, contribution of recruits for the army, and support of the state bureaucracy.  To ensure fulfillment of this administrative function of the state, the Mongols devised an intricate bureaucracy based on the functions of two types of administrators: baskaks (tax oScials who, as military representatives of the central rule, had security obligations in addition to supervision of tax and duty collection) and darugas (civil representatives who supervised tax collection and also acted as provincial governors).  Although documents do not confirm the existence of either baskaks or darugas in the Bulgar lands, such administrators (at least darugas) were probably known in the Middle Volga during the Golden Horde period because these terms were known at the time of the Kazan khanate, where, however, they designated provinces rather than tax officials. 
In addition to Mongol tax officials, a category of tax collectors (tamghachi) and service people (soiurghal) from among the local population added to the number of those charged with the operation of the Mongol administrative system.  Only one social group was exempt from taxes: the tarkhan, a privileged nobility who held hereditary land grants given to them by the khan, most likely in return for some type of military service. 
It would be erroneous to contend that Mongol rule affected equally the political life, economic patterns, social structure, and culture of the principalities in the Middle Volga. The principle of indirect rule, which occupied a significant place in the sociopolitical system of the Golden Horde, was responsible for the preservation of the ruling class and local dynasties until 1445.
The Mongol tax system was indirectly responsible for an increased stratification of the population in the Middle Volga area. The landed aristocracy had always represented the upper level of the former Bulgar state. It continued to enjoy that position under the Mongol khans, but it was no longer a homogeneous class. The emergence of soiurghals and tarkhans contributed to the stratification of the aristocracy while also being responsible for significant differences that emerged among the peasantry; this was because tarkhans owned peasants who were de facto serfs or had lost their freedom at least partially.
In addition to the emergence of a category of dependent peasants, the deterioration of the economic status of the free peasantry represented one of the important developments that affected the rural population of the Middle Volga under Mongol rule. The obligations of the peasants increased as kalan (the land tax paid in kind), and urtak (the land rent paid in services) were increased. The craftsmen and merchants continued to occupy an important place in the social structure of the principalities of the Middle Volga, but they, too, underwent a process of gradual stratification. 
The Bulgar lands recovered gradually from the destruction and disruption of economic life that accompanied their conquest. Agriculture, cattle breeding, crafts, and trade still represented the backbone of the economy. During the period immediately following the conquest, however, the exodus of the population to the north seriously affected agriculture and rendered a blow to urban life. Cities were deprived of skilled craftsmen, who were taken prisoner and sent to the south to build and beautify the cities of Golden Horde.
Some cities, such as Biliar, never recovered from the Mongol conquest. By the late thirteeth and early fourteenth centuries, however, Bulgar, Suvar, and other old centers experienced a revival. Bulgar, in particular, boasted a dynamic urban life during the fourteenth century: A city of 50,000, it was, above all, a trade center that attracted merchants from Russia as well as the Muslim East and became known as the Golden Throne (Altyn Taht) of the Mongol khans. In addition, new cities, such as Kashan, Kazan, and Kremenchug emerged, and they represented the main catalysts in the economic recovery; this is attested to by the resumption of coin minting, a clear sign of market revival. 
The process of recovery, however, was hindered by the instability that accompanied the weakening and fragmentation of the Golden Horde and ultimately caused its disintegration. The Bulgar lands absorbed successive waves of shocks: They became the theater of confrontation between Bulat Timur and Toktamysh, who in 1391 and 1395 clashed in their struggle for supremacy and control of Batu's disintegrating ulus. Then, in 1395, the neighboring Russian princes attacked and devastated the entire area. Drought and plague, which ravaged the Middle Volga between 1428 and 1430, added to the devastation and triggered still another wave of migration. The Bulgars once again moved to the north, northwest, and northeast and settled on lands along the Kazanka and Kama, thus contributing to the process of ethnic consolidation around Kazan, or Bulgar-al-jadid (the new Bulgar). Gradually, Kazan gained in prominence, and although it never enjoyed the right to mint coins stamped with the names of its rulers, the throne of the principality was occupied by emirs from the old Bulgar dynasty until 1445, when the throne was taken over by Mahmud, son of Ulu Muhammed, who was the ousted khan of the Golden Horde and the grandson of Toktamysh. Having taken over the throne of the Kazan principality, Mahmud became the founder of the Kazan khanates, which along with the Crimean and Astrakhan khanates, the kingdom of Sibir, and the Nogai Horde became one of the successors of the Golden Horde.
The disintegration of the Golden Horde eliminated many of the common denominators that had held together the heterogenous political and socioeconomic entity forged by Batu Khan. The many lands that had made up the fabric of the Golden Horde embarked on paths of development that grew increasingly distinct, but they all carried the legacy of Mongol rule.
For the Bulgars of the Middle Volga, the most enduring impact of their
incorporation into the Golden Horde was the reinforcement of their Islamic
identity and culture under the catalytic stimuli of an environment that
had become an Islamic-Turkic commonwealth with its beginnings in the fourteenth
century. When the ruling dynasty and the court of the Golden Horde adopted
Islam under Berke Khan, it also adopted the urban culture of the Muslim
East, and Saray became a Muslim city. The intensification of the ties with
the Muslim East, and the increased interaction between the Turkic peoples
of the Golden Horde, must have enhanced the Bulgars' awareness of belonging
to an umma that had a distinctly Turkic cultural profile. The decision
of Khan Ozbek to eliminate Mongol as the language of politics and diplomacy
and replace it with Arabic, as well as his decision to make Turki the offial
language of the Golden Horde, intensified the process of acculturation.
Despite the contentions of the Bulgar-theory purists, the Golden Horde
became to a great extent the melting pot in which the ethnic and cultural
syntheses that shaped the future history of the heirs to the Bulgar state
1. B. Spuler, ed., The Muslim World. The Mongol Period, part 3 (Leiden, 1960), p. 7, and History of the Mongols Based on Eastern and Western Accounts of the Thirteenth and Fourteenth Centuries (Berkeley and Los Angeles, 1972), p. 52; ITASSR (Kazan, 1973), p. 23; A. N. Kurat, "Alton Ordu devleti," in Turk Dunyasi El Kitabt, vol. 2 (Ankara, 1976), p. 929.
2. R. G. Fakhrutdinov, Arkheologicheskie pamiatniki Volzhsko-Kamskoi Bulgarii i ee territorii (Kazan, 1975), p. 50; F. V. Ballod, Privolzhskie Pompei (Moscow and St. Petersburg, 1923).
3. Spuler, Muslim World, pp. 12 – 14.
4. A. N. Kurat, "Alton Ordu kaganhgi," in IV – XVIII yuzysllannda Karadenizin kuzeyindeki Turk kavimleri ve devletleri (Ankara, 1972), pp. 119 – 52.
5. A. G. Mukhamadiev, "Bulgaro-Tatarskaia monetnaia sistema serediny 13v," in Issledovaniia pa istoriografii Tatarii (Kazan, 1978), pp. 126 – 31.
6. Those who settled among the Bashkirs are considered the ancestors of the Teptiars. For a discussion of their ethnogenesis, see G. N. Akhmarov, "Teptiari i ikh proiskhozhdenie," Izvestiia obshchestva arkheologii, istorii i etnografii pri Kazanskom universitete 28 (1908): 340 – 64; R. G. Kuzeev, Istoricheskaia etnografiia Bashkirskogo naroda (Ufa, 1978); and A. Kh. Khalikov, "Obshchie protsessy v etnogeneze Bashkir i Tatar Povolzh'ia i Priural'ia," in Arkheologiia i etnografiia Bashkirii, vol. 4 (Ufa, 1971), pp. 30 – 37.
7. In Khalikov's de6nition of anthropological purity, interaction with various local Finnic and Turkic tribes is acceptable although any Mongol contribution to the ethnic processes of the area is ruled out. A. Kh. Khalikov, Proiskhozhdenie Tatar Povolzhia i Priural'ia (Kazan, 1978), pp. 98 – 99. A similar position is held by Kalinin, who argues that the Bulgar settlers mixed with the local population and set in motion the ethnogenetic process that was to result in the emergence of the Kazan Tatars and to which the Mongols made no contribution. N. F. Kalinin, Kazan. Istoricheskii ocherk (Kazan, 1952), p. 23.
8. ITASSR (1973), p. 28.
9. Kazan, or Iski-Kazan (old Kazan), emerged around 1238 to 1240. However, because present-day Kazan is located at a distance of 45 km. from Iski-Kazan, this date is not valid as the date of its foundation. M. V. Fekhner, Velikie Bulgary. Kazan'. Sviazhsk (Moscow, 1978), p. 11.
10. V. G. Tizengauzen [Tiesenhausen], ed., Sbornik materialov otnosiashchikhsia k istorii Zolotoi Ordy, vol. 2 (Moscow and Leningrad, 1941), pp. 34 – 36.
11. ITASSR (1973), p. 23. On the vassal status of the Bulgar emirs, see G. V. Iusupov, Vvedenie v bulgaro – tatarskuiu epigrafiku (Moscow and Leningrad, 1960), pp. 102 – 3, and G. V. Vernadsky, Zolotaia Orda. Egipet i Vizantiia v ikh vzaimo-otnosheniiakh v tsarstvovanie Mikhaila Paleologa (Prague, 1927).
12. The khans had their winter residences in Gulistan, a suburb of Saray. During the summer, they moved to the country, setting up their tents on the open plains to the north. It was probably this practice that was responsible for the entrenchment of the belief that the capital of the Golden Horde was a tent city. K'urat, "Altin Ordu devleti," p. 930.
13. G. A. Fedorov-Davydov, Obshchestvennyi stroi Zolotoi Ordy (Moscow, 1973), pp. 25-32.
14. A. Battal, Tatar tahiri. Quan Turkleri. Tarihi ve siyasi gorushler (Istanbul, 1925), pp. 20 – 27; I. Berezin, "Ocherk vnutrennego ustroistva Ulusa Dzhuchieva," in Trudy Otdeleniia Imperatorskogo Russkogo Arkheologicheskogo Obshchestva, part 8 (St. Petersburg, 1864), pp. 387 – 494.
15. For a discussion of political and administrative practices of the early Turkic state formations in order to identify their influence on the Mongols, see L. N. Gumilev, "Udel'no-lestvichnaia sistema u tiurok v VI – VII vekakh. K voprosu o rannikh formakh gosudarstvennosti," SE 3 (1959): 11 – 16. For a discussion of the impact of Mongol rule on the nomadic peoples, see G. A. Fedorov-Davydov, Kochevniki Vostochnoi Evropy pod vlast'iu zoloto-ordynskikh khanov. Arkheologicheskie pamiatniki (Moscow, 1966).
16. 1TASSR (1973), p. 25.
17. Spuler, The Muslim World, p. 48; Davydov, Obshchestvennyi stroi, pp. 25 – 32. According to Bartol'd, darugas were military governors; see V. V. Bartol'd, Raboty po istorii i filologii tiurkskikh i mongol'skikh narodov. Sochineniia, vol. 5 (Moscow, 1963-1968), p. 529.
18. R. G. Fakhrutdinov, "Posledstviia Mongol'skogo zavoevaniia v Volzhskoi Bulgarii," in Issledovaniia po istorii Tatarii (Kazan, 1978), p. 122.
19. ITASSR (1973), p. 24; I. P. Petrushevskii, "K istorii soiurgala," SV 6 (1949): 227-47.
20. Kurat, "Alton Ordu Kaganhgi," p. 931. For a discussion of the term and concept of tarkhan, see V. V. Bartol'd, Sochineniia, pp. 182, 284, and 599.
21. The elaborate burial monument erected in 1307 for a jeweler named Shakhidulla, and later discovered in the cemetery of Bulgar, suggests that some craftsmen had joined the notables of their communities. See ITASSR (1973), pp. 25-26.
22. Fakhrutdinov, Arkheologicheskie pamiatniki, p. 123. Based on the size of the mosques, Berezin estimated the size of the population of Bulgar to have been around 50,000. See I. Berezin, "Bulgar na Volge. S risunkami Bulgarskikh drevnostei i nadpisei," in Uchenye zapiski Imperatorskogo Kazanskogo Universiteta (Kazan, 1852), part 3, pp. 74 – 126; Mukhamadiev, "Bulgaro- Tatarskaia monetnaia sistema," pp. 133-39.
23. Khalikov, Proiskhozhdenie Tatar, pp. 101 – 4. For a detailed analysis of the disintegration of the Golden Horde, see B. D. Grekov and A. Iu. Iakubovskii, Zolotaia Orda i ee padenie (Moscow and Leningrad, 1950).