Rus' forces sailed into the Bosporus in a fleet of about 200 vessels and started pillaging the suburbs of Constantinople.

Rus' Khaganate or Kaganate of Rus is a name applied by some modern historians to a hypothetical polity suggested to have existed during a poorly documented period in the history of Eastern Europe between c. 830 and the 890s.

The Bosporus or Bosphorus Strait is a natural strait and an internationally significant waterway located in Turkey which is straddled by the city of Istanbul. The Bosporus connects the Black Sea to the Sea of Marmara and forms one of the continental boundaries between Asia and Europe. It also divides Turkey by separating Asia Minor from Thrace. It is the world's narrowest strait used for international navigation.

The siege of Constantinople in 860 was the only major military expedition of the Rus' recorded in Byzantine and western European sources. The casus belli was the construction of the fortress Sarkel by Byzantine engineers, restricting the Rus' trade route along the Don River in favour of the Khazars. Accounts vary, with discrepancies between contemporary and later sources, and the outcome is unknown in detail.

Constantinople was a historical city located on the Bosporus that served as the capital of the Roman, Byzantine, Latin and Ottoman empires between its consecration in 330 and 1930, when it was renamed Istanbul. Initially as New Rome, Constantinople was founded in 324 during the reign of Constantine the Great on the site of the existing settlement of Byzantium and in 330 became the capital of the Roman Empire. Following the collapse of the Western Roman Empire in the late 5th century, Constantinople remained the capital of the Eastern Roman Empire, the Latin Empire (1204–1261) and the Ottoman Empire (1453–1922). Following the Turkish War of Independence, the Turkish capital moved to Ankara. Although the city had been known as Istanbul since 1453, it was officially renamed Istanbul on 28 March 1930. The city is today the largest city in Europe, straddling the Bosporus strait and lying in both Europe and Asia, and the financial center of Turkey.