As Germany and the Soviet Union engaged in colossal battles during World War II, a much smaller but vicious struggle broke out in the borderlands of southeastern Poland, resurrecting longstanding ethnic and territorial conflicts between Poles and Ukrainians. During the war, both sides organized large partisan armies and sought to establish control over territory each deemed integral to their post-war national visions. The violence reached a fever pitch only in the years immediately following the war. This comprehensive study provides a unique overview to Polish–Ukrainian relations dating back to the tenth century. Examining the development of this long-standing feud as part of a longer historical process that has occurred between the Polish and Ukrainian ethnic groups in Europe, Rapawy takes into consideration centuries of ethnic strife, population shifts that resulted from ethnic conquests, and the formation of national states after the First World War on multi-ethnic territories as a pre-condition for the events that occurred on the years following World War II.