The Polish term Kresy (Polish pronunciation: [ˈkrɛsɨ], Borderlands) refers to a territory that was formerly the eastern provinces of Poland. These territories today lie in western Ukraine, western Belarus, as well as eastern Lithuania, with such major cities, as Lviv, Vilnius, and Hrodna. This territory was included within the Polish-Lithuanian Commonwealth and Second Polish Republic, until World War II. In the interbellum Poland, the term Kresy roughly equated with the lands beyond the Curzon Line, suggested in December 1919 by the British Foreign Office as the eastern border for Poland. In September 1939, after the Nazi-Soviet Pact, these territories were incorporated into the Soviet republics of Ukraine, Belarus and Lithuania. These Soviet gains were ratified by the Western Allies at the Tehran conference, the Yalta conference and the Potsdam conference. When the Soviet Union broke up, they remained part of those respective republics as they gained independence. Even though Kresy, or the Eastern Borderlands, are no longer Polish territories, the area is still inhabited by a significant Polish minority, and the memory of a Polish Kresy is still cultivated. The attachment of the "myth of Kresy", the vision of the region as peaceful idyllic rural land, has been criticized in Polish discourse. Economically the region was the poorest in interwar Poland, and had the lowest literacy level of the nation, which was the result of more than one hundred years of Austro-Hungarian and Russian rule, as education was not compulsory in the Russian Empire.