The Mongolian invasion, which influenced the future of many European and Asian states and nations in the first half of the XIII century, also covered Bulgaria of the Volga Region. The first Mongolian intrusion in 1223 was beat by Bulgars, defeating the best commanders of Chinghiskhan. However, forces were unequal, and in 1236 a big army commanded by Batu-khan conquered the Bulgaria, cutting and burning everything around. Estates on the other side of the Kama River were ruined, as many towns and villages were burnt to ashes. Some people of this area were slaved; the others ran to the North. The Bulgar State was divided into several feudal estates, belonging to the Ulus Dzhuchi (the Golden Horde) as vassalage.

Step by step the country began reviving after the defeat. Destroyed cities of Bolgar and Dzhuketau were built again quickly, and new ones, such as Kermenchuk and Tubulgatau appeared. Profitable location of the Bulgar estates on the trade crossroads from Northern Europe and Russia to the Lower Volga Region and Central Asia as well as the policy of Ulus Dzhuchi khans, who supported trade and toleration, promoted new political and commercial links. Cities, situated on the banks of the Volga and the Kama rivers, became the main trade ways of Ulus Dzhuchi.

The time of the highest political and economical power of Dzhuchids’ Empire covered the period from the end of the XIII century to the first half of the XIV century. At that time, at the upsurge of economy and trade, the central power was strengthened, implying common governmental system, stable boundaries and the end of internecine wars. Dozens of big cities sprung up, where people formed a single literary language and rich emperor culture. Islam was adopted as the State religion. The military nobility of the Golden Horde, which consisted of Bulgar and Kupchak aristocracy clans, was formed at the same time, presenting a type of new Tatar community consciousness.

Bulgar estates were also developed intensively. Traditional basis for economy was agriculture, stalled keeping of cattle, and different handicrafts, such as blacksmith’s work, armourer’s, pottery, bone carver’s and jeweller’s art.The originality of Bulgar culture was stipulated by the combination of common Golden-Horde tendencies and Pre-Mongolian traditions. In spite of the conquest there were no many nomad migrations to Bulgaria. As a rule, only Tatar nobility with their army moved there. Nevertheless, they dominated the Bulgar life and gradually subdued the Bulgar aristocracy, including them in their clan system. Constant development of Bulgar outlying districts resulted in increased number of rural and trade settlements. By the beginning of the XIV century they already had stronger economy. It led to the consolidation of the cities, which were the centers of these lands: Kazan, Kashan and Chalpy in the Kama river region as well as Tetesh and Yapanche in the Volga river region.

Kazan, situated near the northern boundaries of the country and on the way from the Volga river to the North of the Upper Kama river region, had been an important strategic point even before. But in the Golden Horde period the city became the centre of wide territory – lands of the Kazanka river basin (Kazan Arty – Transkazan area). It could be possible, that Kazan was a place of tax and tribute collection for the khans of Ulus Durchi. The geographical position, profitable for trade, together with economical growth promoted increasing political power of the Kazan rulers. According to the gravestone, found in the suburb of the city, in the end of the XIII century the Kazan ruler Khasanbek, the son of Mir-Makhmud, had a grand title of “Great sultan, the most notable sultan’s mate, honored emir…, a victorious … pride of people and belief, the God’s shadow”. The title is a significant fact of sultan’s status, which was equal to the status of the Bolgar ruler and the khan’s vassal of Ulus Dzhuchi.

Great changes in the political life of the Bulgar sultans fell on the 60th of the XIV century, when Ulus Dzhuchi suffered from crisis. Rulers of vassal estates became more and more independent while weakening the central power. The success of one or another candidate to the khan’s throne depended on them, and the rulers began participating in intestine wars within the Golden Horde territory. Among them were the sultans of Bolgar and Dzhuketau, who had the strongest power in the Bulgar state. In 1361 emir Bulat-Timur occupied Bolgar, trying to strengthen his power in the Horde. In 1376 Bolgar was besieged by Moscow forces by the order of emir Mamai, thus, Bulgar estates became the Moscow protectorate. Pirates from Novgorod, the so-called ushkuiniks, frequently raided the territories on the banks of the Volga and the Kama rivers. As a result of the wars and forays Bolgar began losing its dominating status, while Kazan was becoming stronger.

The city sprung up evidently during the XIII-XV centuries, but its lay-out didn’t change a lot. The city citadel was expanded up to 400 meters, and its square reached 10 hectares. However, the streets with wooden flooring, which had appeared earlier, still remained. People began to construct stone and brick buildings. Fragments of a tower (or minaret) were found in the citadel as well as a number of white-stone constructions, namely a mausoleum and, possibly, a mosque. The most valuable and expensive things, used in every-day life, were found there. From the South, East and West the citadel joined trading quarters, which hadn’t strong protection. Fragments of a copper-founding (excavations of 1971) and tanning (excavations of 1953-1988) workshops were found there as well as some traces of pottery and hardware. At that time the city was an important trading center of the Volga region. This fact is proved by numerous finds of Chinese porcelain, kashin dishes from Middle-Asia and vessels of spherical and conic shape.

Several city cemeteries date from the same time, for example, in the place, where the State Museum of Tatarstan is situated now, and in the Kremlin, near the building of the Ministry of Agriculture of Tatarstan. Both cemeteries were for Moslem people. Well-known grave-stones, dated the end of the XIII century (1297), are also from one of the city cemeteries. A buried treasure of 597 coins, found in 1893, date from the first third of the XV century.

The Kazan was first mentioned in Russian chronicles together with Dzhuketau in 1391. During the great campaign of the prince Yury Dmitriyevich to Bulgaria in 1399 the Kazan city was called the centre of sultans alongside Bolgar Dzhuketau and Kermenchuk. At that time they began to mint coins in Kazan, stamping the place of the coinage on the money, namely “Bulgar al-Dzhadid’, i.e. New Bulgar. All these facts evidence the increasing military power and political influence of the Kazan sultans, their stronger aspiration to sovereignty during the period from the end of the XIV to the beginning of the XV centuries.

The most important step in all Bulgar estates unification was enthroning Ghiyas Ad-din, who came from the Dzhuchids (1422-1438/1445?). At the time of his governing currency reform was held in Kazan, and they began to mint coins with his “The Greatest Sultan” title and emblem, representing tamga in the shape of lyre.

Kazan also tried to influence internal life, but the attempts were not a success. Since 1426 coins were minted on behalf of Ulus Dzhuchi khans. Defeats in the wars with Moscow Great Princedom, such as Bolgar city destruction in 1431, showed Bulgar rulers’ inability to resist separately Moscow forces and the lack of help from the Horde khans, being involved in intestine wars.