The article is dedicated to the Rus' military campaign against Bardha'a, a major political center in Azerbaijan in the era of the Abbasid Caliphate. This was the military action of the Rus' in the Caspian region, which found the most complete consecration in the written sources of the East. In the context of political events, the arrival of Rus' in Azerbaijan should be at� tributed to August 944, and the departure from there at the turn of summerautumn 945. The likely participants of the campaign were contingents from the army of Prince Igor of Kyiv, who in 944 went on a campaign against Byzantium, which ended in peace negotiations. The campaign against Bardha'a took place with the support of Khazaria. Rus' arrived in Azerbaijan by ship, so their most likely route is: the Black Sea -the Kerch Strait -the Sea of Azov -the Don -portage to Sarkel -the Volga -the Caspian Seathe Kura. The version about the land route through the North Caucasus is not valid, and through the lands of the Byzantine vassals of Abkhazia, Kakheti, and Hereti is not confirmed by source information. The Rus' cam� paign against the Bardha'a became possible in the context of a serious crisis that the Caliphate was experiencing. One of the manifestations of the crisis was the growing popularity of opposition religious trends. Ismailism occu� pied a special place among such trends, including in the form of Qarmatian teaching. The Emir Marzuban, an opponent of the Rus in Bardha'a, consi� � dered himself as belonging to this teaching. Countering the Ismaili was one