Rising northwest of Moscow and flowing 2,200 miles southeast to the Caspian Sea, the Volga is Europe’s longest river. Passing through pine forests, black-earth steppe and semi-desert, it is simultaneously part of Russia’s heartland and a marker of the border between Europe and Asia. For Russians, the river is ‘Mother Volga’, subject of song and story, and the backdrop to Stalingrad, site of the most sacralised battle of the Great Patriotic War. But for Russia’s ethnic minorities, the river is also where Russia began turning itself into an empire, with Ivan the Terrible’s conquest, in the 1550s, of the Volga khanates of Kazan and Astrakhan. How Russia’s policy towards its different nationalities developed subsequently is one of the most interesting strands of this lucid and well-researched book.

The story starts back in the seventh century, with the shadowy kingdom of Khazaria. Although no Khazar-language records survive, we know from Arabic sources that the kingdom lasted around three and a half centuries, extracting tribute from an enormous area ranging from the Aral Sea to Crimea. Now long sunk