Between 1943 and 1945, Ukrainian nationalists attacked 99 Polish towns and villages in Wolyn, a Nazi-occupied region of Poland and is now part of Ukraine, and massacred thousands of Poles. It is estimated that around 100,000 Poles died at the hands of Ukrainian nationalists.
The killings were initiated and directed by a radical Ukrainian nationalist Stepan Bandera and his Organization of Ukrainian Nationalists and its military arm, the Ukrainian Insurgent Army. Ukrainian villagers eagerly participated in the massacre. Their goal was to purge all non-Ukrainians from a future Ukrainian state. They wanted not only to purge Polish civilians, but also to erase all traces of Polish presence in the area.