During the height of World War II, the Ukrainian Insurgent Army (UPA) initiated a campaign of violence against Polish populations in Volhynia and Eastern Galicia. This event is marked by a series of coordinated attacks against Polish villages, resulting in thousands of deaths and the destruction of numerous settlements. The UPA sought to establish a Ukrainian nation-state, which led them to believe eliminating Polish presence in these regions was essential. The violence was particularly brutal, characterized by massacres where civilians were targeted without mercy, often employing extreme methods to ensure compliance with their objectives.

The campaign unfolded in a landscape shattered by war, where shifting allegiances and nationalist sentiments fueled hostilities. Notable for its scale, the actions taken by the UPA not only resulted in immediate loss of life but also sowed deep-seated ethnic tensions that would hinder post-war reconciliation efforts in the region. The violence led to a mass exodus of Poles from Volhynia, fundamentally changing the demographic makeup of the area.

Following these events, the response from Polish armed groups and the underground government became increasingly aggressive, leading to a cycle of revenge attacks. The UPA's campaign would later be framed within the broader context of regional conflicts involving various ethnic and nationalist groups competing for territory and identity during and after the war, leaving an indelible mark on Ukrainian-Polish relations.