The conflict,sometimes called a civil war occured after the massacre of Poles in Volhynia, an ethnic cleansing operation in the eastern part of occupied Poland.The entire conflict has occured between late March 1943 to August 1947, extending beyond WW2. Along the Galicia and Eastern Lublin area, total Polish civilian losses exceed 60,000.The massacres committed by the UPA led to ethnic cleansing and retaliatory killings by Poles against local Ukrainians both east and west of the Curzon Line. Estimates of the number of Ukrainians killed in Polish reprisals vary from 10,000 to 20,000, in all areas affected by the conflict. Due in part to the successive occupations of the region, ethnic Poles and Ukrainians were brutally pitted against each other, first under the German occupation, and later under the Soviet occupation. Thousands on both sides lost their lives during the course of the conflict.