The proposed study describes the causes and course of the Polish-Ukrainian armed conflict in Volyn during the Second World War. Attracting a large number of new documents to scientific circulation, including from former secret archives, the author comes to the conclusion that the confrontation between both peoples was primarily due to the rejection by the Polish political elite and part of the Poles of the Ukrainians' aspirations to create their own statehood on the original Ukrainian land. It is also noted that both the Nazis and the Bolsheviks were interested in inciting the armed Polish-Ukrainian conflict. Designed for everyone who wants to understand the problem of Polish-Ukrainian relations in 1939-1947.