The collapse of Polish rule in the Ukraine in the mid-seventeenth century changed the course of East European history. The great Cossack revolt of 1648 exposed the weaknesses of the Polish-Lithuanian Commonwealth. After the emergence of a Ukrainian polity, a struggle for dominance ensued, paving the way for the Russian annexation of the Ukraine. Frank Sysyn examines the failure of Polish policy through the career of Adam Kysil. A leader of the Ukrainian nobility and an official of the Polish government, Kysil was ideally suited to serve as the mediator between the rebels and the government. His failure signaled the already irreconcilable differences that divided them. Based on extensive archival research in Poland and the USSR, Sysyn's study is a contribution not only to scholarship on Eastern Europe, but also to discussions on the preconditions and nature of early modern revolts and on the change of political and social elites.