The enemy went by many names. Known to the Rus as the Polovtsy, and elsewhere as Cumans or Kipchaks, they were mounted nomads of the southern grasslands who first appear in the Rus chronicles around 1055, when Prince Vsevolod made peace with them. The peace did not hold. In 1061 they breached the old earthworks and palisades that earlier princes, Vladimir and Yaroslav, had built against such raids, and defeated a Rus army. By 1068 the threat had grown into a full invasion, and the grand prince of Kyiv, Iziaslav, rode out with his brothers Sviatoslav of Chernihiv and Vsevolod of Pereiaslav to meet the Cumans on the Alta and turn them back.

The meeting went badly. On the Alta the Rus forces were broken and scattered, and the princes fled back to Kyiv and Chernihiv, their armies in pieces. In Kyiv the mood curdled into anger. The people gathered in a veche, a public assembly in the marketplace, and demanded arms so they could march out and fight the raiders themselves. When the grand prince refused to hand over weapons, the crowd turned on the authorities, ransacking the house of the voivode Konstantin. Then they did something extraordinary: they broke open the prison, freed Prince Vseslav of Polotsk, whom the ruling brothers had jailed, and placed him on the throne of Kyiv in the hope that he might do what they could not, and stop the Cumans.

Iziaslav did not accept his fall quietly. Driven from his own capital, he fled west to his father-in-law, Boleslaw II of Poland, and returned the following May of 1069 with Polish military backing to reclaim the throne. The episode became a favorite example for later historians of the surprising power of the veche, the assembled townspeople whose collective will could, in Kyiv as in Novgorod the Great, reach up and shake the politics of princes. For one turbulent year, the men of the marketplace had unseated a grand prince and chosen his replacement, a reminder that in the Rus cities, rulers ignored the popular voice at their peril.

The story did not end in disgrace. While Iziaslav was in exile, his brother Sviatoslav gathered his forces and, on the first of November 1068, defeated a Cuman army said to be far larger than his own, stemming the tide of raids. After that victory the steppe fell quiet; only a small skirmish in 1071 disturbed the peace, and the Cuman threat to Kyiv and Chernihiv receded for the better part of two decades. So the Alta River holds a double memory: the shame of a rout that toppled a throne, and, close behind it, the relief of a hard-won recovery. The little river near Pereiaslav flows on unremarkably today, giving no sign that the fate of Kyiv once turned along its banks.