Ivan Lytvynchuk and Petro Oliynyk. The ethnic cleansing operation against the Poles began on a large scale in Volhynia in late February (or early Spring) of that year and lasted until the end of 1944. Taras Bulba-Borovets, the founder of the UPA, criticized the attacks as soon as they began: 11 July 1943 was one of the deadliest days of the massacres, with UPA units marching from village to village, killing Polish civilians. On that day, UPA units surrounded and attacked 99 Polish villages and settlements in three counties – Kowel, Horochów, and Włodzimierz Wołyński. On the following day, 50 additional villages were attacked. In January 1944, the UPA campaign of ethnic cleansing spread to the neighbouring province of Galicia. Unlike in Volhynia, where Polish villages were destroyed and their inhabitants murdered without warning, Poles in eastern Galicia were in some instances given the choice of fleeing or being killed. Ukrainian peasants sometimes joined the UPA in the violence, and large bands of armed marauders, unaffiliated with the UPA, brutalized civilians. In other cases however, Ukrainian civilians took significant steps to protect their Polish neighbours, either by hiding them during the UPA raids or vouching that the Poles were actually Ukrainians. The methods used by UPA to carry out the massacres were particularly brutal and were committed indiscriminately without any restraint. Historian Norman Davies describes the killings: "Villages were torched. Roman Catholic priests were axed or crucified. Churches were burned with all their parishioners. Isolated farms were attacked by gangs carrying pitchforks and kitchen knives. Throats were cut. Pregnant women were bayoneted. Children were cut in two. Men were ambushed in the field and led away." In total, the estimated numbers of Polish and Jewish civilians killed in Volhynia and Galicia is between 50,000 and 100,000. Victims of the UPA included Ukrainians who did not adhere to its form of nationalism and so were considered traitors. After the initiation of the massacres, Polish self-defense units responded in kind. Estimates of Ukrainians killed in acts of reprisal range from 2,000 to 30,000. On 22 July 2016, the Sejm of the Republic of Poland passed a resolution declaring the massacres committed by UPA a genocide. Post-war After Galicia had been taken over by the Red Army, many units of UPA abandoned the anti-Polish course of action and some even began cooperating with local Polish anti-communist resistance against the Soviets and the NKVD.