The Wisla Operation
Operation Wisła (Polish: Akcja Wisła) was the codename for the 1947 deportation of southeastern Poland's Ukrainian, Boyko and Lemko populations, carried out by the Soviet installed communist authorities in Poland with assistance from Soviet Union and Communist Czechoslovakia. The stated goal of the operation was to suppress the Ukrainian Insurgent Army (UIA), which had allegedly been terrorizing and murdering Poles in those southeastern territories since 1944. About 200,000 people, mostly of Ukrainian ethnicity, residing in southeastern Poland were, often forcibly, resettled to the "Recovered Territories" in the north and west of the country. The operation was named after the Vistula River, Wisła in Polish.
After the fall of communism, the operation was condemned by Polish and Ukrainian politicians and historians. It has been described as an ethnic cleansing by Polish and Western sources as well as by Ukrainians.