When the Germans began to suffer defeat on the Eastern Front, the OUN felt that there would be no better time to fight for independence. The UPA – Ukrainian Insurgent Army – was established. It was led by Roman Shuchevych. And almost on the spur of the moment, he began to implement the plan of ethnic cleansing that had emerged in the 1930s.
They started in February 1943 with the village of Parosla, where about 150 people were killed. Subsequently, the UPA attacked more villages inhabited by Poles – often carrying out the attacks in such a way as to make them look like spontaneous peasant actions. These actions were characterised by very high cruelty. This was to make them look like a peasant uprising against the Polish lords. On more than one occasion, local Ukrainian peasants were urged or coerced into complicity.
The anti-Polish action culminated on 11 July, the so-called 'Bloody Sunday'. On that day, almost a hundred villages were attacked. In July 1943, several thousand people were killed in Volhynia. In total, more than tens of thousands of Poles were killed in Volhynia alone during the 1943 and 1944 actions. One of the symbols of those events is the ruins of the old, Carmelite church in Kisielin, where the Poles gathered there were attacked.