The Cumans again invaded Kievan Rus' in 1068. The three brothers united their forces against them, but the Cumans routed them on the Alta River. After their defeat, Vsevolod withdrew to Pereyaslav. However, its citizens rose up in open rebellion, dethroned Iziaslav, and liberated and proclaimed Vseslav their grand prince. Vsevolod and Sviatoslav made no attempt to expel the usurper from Kiev.