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Rise of the Rus' and the collapse of the Khazarian state

By the 9th century, groups of Varangian Rus', developing a powerful warrior-merchant system, began probing south down the waterways controlled by the Khazars and their protectorate, the Volga Bulgarians, partially in pursuit of the Arab silver that flowed north for hoarding through the Khazarian-Volga Bulgarian trading zones, partially to trade in furs and ironwork. Northern mercantile fleets passing Atil were tithed, as they were at Byzantine Cherson. Their presence may have prompted the formation of a Rus' state by convincing the Slavs, Merja and the Chud ' to unite to protect common interests against Khazarian exactions of tribute. It is often argued that a Rus' Khaganate modelled on the Khazarian state had formed to the east and that the Varangian chieftain of the coalition appropriated the title of qağan (khagan) as early as the 830s: the title survived to denote the princes of Kievan Rus', whose capital, Kiev, is often associated with a Khazarian foundation. The construction of the Sarkel fortress, with technical assistance from Khazaria's Byzantine ally at the time, together with the minting of an autonomous Khazar coinage around the 830s, may have been a defensive measure against emerging threats from Varangians to the north and from the Magyars on the eastern steppe. By 860, the Rus' had penetrated as far as Kiev and, via the Dnieper, Constantinople.

Alliances often shifted. Byzantium, threatened by Varangian Rus' raiders, would assist Khazaria, and Khazaria at times allowed the northerners to pass through their territory in exchange for a portion of the booty. From the beginning of the 10th century, the Khazars found themselves fighting on multiple fronts as nomadic incursions were exacerbated by uprisings by former clients and invasions from former allies. The pax Khazarica was caught in a pincer movement between steppe Pechenegs and the strengthening of an emergent Rus' power to the north, both undermining Khazaria's tributary empire. According to the Schechter Text, the Khazar ruler King Benjamin (ca.880–890) fought a battle against the allied forces of five lands whose moves were perhaps encouraged by Byzantium. Although Benjamin was victorious, his son Aaron II faced another invasion, this time led by the Alans, whose leader had converted to Christianity and entered into an alliance with Byzantium, which, under Leo VI the Wise, encouraged them to fight against the Khazars.

By the 880s, Khazar control of the Middle Dnieper from Kiev, where they collected tribute from Eastern Slavic tribes, began to wane as Oleg of Novgorod wrested control of the city from the Varangian warlords Askold and Dir, and embarked on what was to prove to be the foundation of a Rus' empire. The Khazars had initially allowed the Rus' to use the trade route along the Volga River, and raid southwards. See Caspian expeditions of the Rus'. According to Al-Mas'udi, the qağan is said to have given his assent on the condition that the Rus' give him half of the booty. In 913, however, two years after Byzantium concluded a peace treaty with the Rus' in 911, a Varangian foray, with Khazar connivance, through Arab lands led to a request to the Khazar throne by the Khwârazmian Islamic guard for permission to retaliate against the large Rus' contingent on its return. The purpose was to revenge the violence the Rus' razzias had inflicted on their fellow Muslim believers. The Rus' force was thoroughly routed and massacred. The Khazar rulers closed the passage down the Volga to the Rus', sparking a war. In the early 960s, Khazar ruler Joseph wrote to Hasdai ibn Shaprut about the deterioration of Khazar relations with the Rus': "I protect the mouth of the river (Itil-Volga) and prevent the Rus arriving in their ships from setting off by sea against the Ishmaelites and (equally) all (their) enemies from setting off by land to Bab."

The Rus' warlords launched several wars against the Khazar Qağanate, and raided down to the Caspian sea. The Schechter Letter relates the story of a campaign against Khazaria by HLGW (recently identified as Oleg of Chernigov) around 941 in which Oleg was defeated by the Khazar general Pesakh. The Khazar alliance with the Byzantine empire began to collapse in the early 10th century. Byzantine and Khazar forces may have clashed in the Crimea, and by the 940s emperor Constantine VII Porphyrogenitus was speculating in De Administrando Imperio about ways in which the Khazars could be isolated and attacked. The Byzantines during the same period began to attempt alliances with the Pechenegs and the Rus', with varying degrees of success. A further factor undermining the Khazar Qağanate was a shift in Islamic routes at this time, as Muslims in Khwarazmia forged trade links with the recently converted Volga Bulgarian Muslims, a move which may have caused a drastic drop, perhaps up to 80%, in the revenue base of Khazaria, and consequently, a crisis in its ability to pay for its defence.

Sviatoslav I finally succeeded in destroying Khazar imperial power in the 960s, in a circular sweep that overwhelmed Khazar fortresses like Sarkel and Tamatarkha, and reached as far as the Caucasian Kassogians/ Circassians and then back to Kiev. Sarkel fell in 965, with the capital city of Atil following, c. 968 or 969.

In the Russian chronicle, the vanquishing of the Khazar traditions is associated with Vladimir's conversion in 986. According to the Primary Chronicle, in 986 Khazar Jews were present at Vladimir 's disputation to decide on the prospective religion of the Kievan Rus'. Whether these were Jews who had settled in Kiev or emissaries from some Jewish Khazar remnant state is unclear. Conversion to one of the faiths of the people of Scripture was a precondition to any peace treaty with the Arabs, whose Bulgar envoys had arrived in Kiev after 985.

A visitor to Atil wrote soon after the sacking of the city that its vineyards and garden had been razed, that not a grape or raisin remained in the land, and not even alms for the poor were available. An attempt to rebuild may have been undertaken, since Ibn Hawqal and al-Muqaddasi refer to it after that date, but by Al-Biruni 's time (1048) it was in ruins.