Poland and Ukraine’s bloody past overshadows their anti-Russia alliance – POLITICO

WARSAW — Poland and Ukraine are close allies when it comes to defeating their common enemy Russia — but their own bloodstained history is now straining Kyiv-Warsaw relations. 

During World War II a guerrilla group called the Ukrainian Insurgent Army (known by its Ukrainian acronym UPA) slaughtered tens of thousands of Poles in an effort to ethnically cleanse lands that had been part of Poland before the war but are now in western Ukraine.

Thousands of Ukrainians died in retaliatory attacks; some Ukrainian historians put part of the blame for the killings on long-standing Polish repression of Ukrainian national aspirations before the war.