Zakerzonia

Zakerzonia (Закерзоння; Zakerzonie) is an informal name for the territories of Poland to the west of the Curzon Line which used to have sizeable Ukrainian (and Rusyn) populations, including significant Lemko, Boyko populations, before the invasion of Poland by the Soviet Union and Nazi Germany in 1939, and were claimed as ethnically Ukrainian territories by Ukrainian nationalists in the aftermath of World War II. However, before 1939, the areas of Zakerzonia were mostly inhabited by Poles, who constituted about 70% of the population of this area. Ukrainians lived in a minority in Zakerzonia, constituting about 20% of the area's population.

"Zakerzonia" stands for "territory beyond the Curzon line", or in Ukrainian "Zakerzons'kyi krai".

The Ukrainian Insurgent Army (UPA), at the height of their control of the territories, claimed plans of creation of Transcurzon Republic.

The demography of Zakerzonia drastically changed by forcible resettlement of the Ukrainians, with ethnic cleansing operations being the resettlement of Ukrainians from Poland to the Soviet Union (1944–1946) and Operation Vistula (1947). Therefore, Poles today constitute over 95% of the population of Zakerzonia.

Ukrainians in Zakerzonia in the 1931 census
The last census before World War II carried out in Zakerzonia was the Polish census of 1931.

The results of the 1931 census (questions about mother tongue and religion) in three voivodeships encompassing Zakerzonia:

Ukrainian/Ruthenian (language) and Greek Catholic/Orthodox (religion) majority minority counties are highlighted with yellow. In total within Zakerzonia (area which today belongs to Poland) in these three pre-war voivodeships there were in 1931 almost 392,000 people with Ukrainian or Ruthenian mother tongue and about 625,000 people whose religion was either Orthodox or Uniate (Greek Catholic). This does not include some parts of Sokal, Rava-Ruska, Yavoriv, Mostyska, Dobromyl and Turka counties which remained in Poland. Perhaps 1/3 of the population of these counties remained in Poland, which would give an additional almost 123,000 Ukrainian/Ruthenian-speakers and 141,000 Uniate/Orthodox people.

Ukrainians in Poland: 1939–1950
Piotr Eberhardt estimates that in 1939 the number of Ukrainians between the Curzon Line and Oder–Neisse line was 657,500 people.

Timothy Snyder gives a similar estimate of up to 700,000 Ukrainians or Ukrainian-language speakers living in Poland within its new borders immediately after World War II. They were a "demographic majority in many areas along a long border strip running from Chełm almost to Kraków". His data, however, are not considered reliable, because, for example, the area near Kraków, Tarnów, Rzeszów, Zamość and others has been purely Polish for centuries.

In 1946, only 220,200 Ukrainians were left in Poland, and the figure had further decreased to 150,000 by 1950.