In the Volhynia (Volyn) area of north western Ukraine, local Ukrainian nationalists formed themselves into a resistance army, the Ukrainian Uprising Army (UPA) to fight the Nazi occupiers. Unfortunately their anger turned against the local Polish minority. (In the area lived some 346,000 Poles) In an attempt to drive all Poles out of Wolhynia and Ukraine, in anticipation of an independent Ukrainian state after the war, the UPA started a war of ethnic cleansing that was to prove disastrous for both populations.

The UPA marched from village to village and killed all civilians of Polish nationality. Some 167 towns and villages were entered in this orgy of slaughter. In the village of Poryck, 157 Polish civilians were shot while attending mass in the local Catholic church.

These massacres continued for a year in the rural areas until all Polish residents were either killed or expelled from their homes. These ethnic massacres were completely ignored by the German occupation forces. The exact number of Poles murdered remains unknown but is estimated by a number of historians to be in the region of 35 to 60 thousand.

In this ethnic strife period around 20,000 Ukrainians were killed by Poles. In July, 2003, on the 60th anniversary of the massacres, the presidents of the two nations, Poland and Ukraine, called for a move towards reconciliation and mutual forgiveness. Today, there are over 600 mass grave sites in Volhynia containing the bodies of murdered Polish civilians.