In 1943 at the Teheran Conference, Stalin handed over to Poland the lands west of the Boh River, home to nearly one million Ukrainians. To protect the Ukrainian populat...展开ion, the Organization of Ukrainian Nationalists (OUN) created a clandestine network of operatives and military units. One of these units was a company of the Ukrainian Insurgent Army led by Mykhailo Duda-Hromenko. In 1947 the Polish Communist authorities, in collaboration with the Soviet MGB, carried out Operation Vistula, a forced deportation of Poland's Ukrainians in order to crush the nationalist underground resistance. About 200,000 civilians, residing in southeastern Poland were forcibly resettled to the new territories, former German territory added after World War II, now in the north and west of Poland. After the fall of communism in Eastern Europe, the operation was condemned by some Polish and Ukrainian politicians and historians.