[1] Following the end of World War II in Europe, most of Western Belorussia was ceded to the Soviet Union by the Allies, while some of it, including Białystok, was given to the Polish People's Republic.

[6] The territories of contemporary Belarus, Poland, Ukraine, and the Baltic states were a major theatre of operations during World War I; all the while, the Bolshevik Coup overturned the interim Russian Provisional Government and formed Soviet Russia.

The Bolsheviks withdrew from the war with the Central Powers by signing the Treaty of Brest-Litovsk,[7] and ceded Belarus to Germany for the next eight and a half months.

[citation needed] The German high command used this window of opportunity to transfer its troops to the Western Front for the 1918 Spring Offensive, leaving behind a power vacuum.

[citation needed] The same Rada charter also declared that the Treaty of Brest-Litowsk of March 1918 was invalid because it was signed by foreign governments partitioning territories that were not theirs.

Thus, the almost unsolicited national state, which arose during the First World War, owed its existence directly to the alternative German, Russian and Polish attempts to secure control over the area.

— Tania Raffass [13]In the Second Constituent Charter, the Rada abolished the right to private ownership of land (paragraph 7) in line with the Communist Manifesto.

[17] Following the Peace of Riga, thousands of Poles settled in the area, many of them (including veterans of armed struggle for Poland's independence) were given land by the government.

[19] Józef Piłsudski negotiated with the Western Belorussian leadership,[20] but eventually abandoned the ideas of Intermarium, his own proposed federation of partially self-governing states on the lands of the former Polish–Lithuanian Commonwealth.

[22] In the spring of 1923, Polish prime minister Władysław Sikorski ordered a report on the situation of the Belarusian minority in Poland.

In January 1921, the starosta from Wilejka wrote of the popular mood as being one of resignation and apathy among the Western Belorussian peasants, impoverished by food requisitions by the Bolsheviks and the Polish military.

[23] In 1928 there were 69 schools with Belarusian language in Western Belorussia; the attendance was minimal due in part to lower quality of instruction.

[30] Władysław Studnicki, an influential Polish official, stated that Poland's engagement in the East amounts to a much needed economic colonization.

[38] The operation caused the deaths of up to 250,000 people – out of an official ethnic Polish population of 636,000 – as a result of political murder, disease or starvation.

This image was attractive to many Western Belorussian national leaders, and some of them, like Frantsishak Alyakhnovich or Uładzimir Žyłka emigrated from Poland to the BSSR, but very soon became victims of Soviet repression.

Belarusian/Poleshuk("Tutejszy")/Russian and Orthodox/Greek Catholic plurality or majority counties are highlighted with yellow, while Polish and Roman Catholic plurality or majority counties are highlighted with pink: Soon after the Nazi-Soviet invasion of Poland following the Nazi–Soviet Pact, the area of Western Belorussia was formally annexed into the Belarusian Soviet Socialist Republic (BSSR).

The Soviet secret police NKVD, aided by the Red Army, organized staged elections which were decided in the atmosphere of intimidation and state terror.

[50] In August 2009, on the occasion of the 70th anniversary of the Soviet invasion, the authoritative Polish Institute of National Remembrance announced that its researchers reduced the estimate of the number of people deported to Siberia to 320,000 in total.

[52] The terms of the Molotov–Ribbentrop Pact signed earlier in Moscow were soon broken, when the German Army entered the Soviet occupation zone on 22 June 1941.

After Operation Barbarossa, most of Western Belorussia became part of the German Reichskommissariat Ostland (RKO), as the so-called Generalbezirk Weißruthenien (General Region of White Ruthenia).

[54][55] Known to the Germans as the Schutzmannschaft, the ethnic Belarusian police played an indispensable role in the Holocaust in Belarus,[56][57] notably during the second wave of the ghetto liquidations,[58] starting in February–March 1942.

Most of Western Belarus remained part of the BSSR after the end of World War II in Europe; only the region around Białystok (Belostok) was to be returned to Poland.

[33] Because of bad economic conditions and national discrimination of Belarusian in Poland, much of the population of Western Belorussia welcomed the annexation by the USSR.

[33] The population grew less loyal as the economic conditions became even worse and as the new regime carried out mass repressions and deportations that targeted Belarusians as well as ethnic Poles.

[33] Immediately after the annexation, the Soviet authorities carried out the nationalization of agricultural land owned by large landowners in Western Belorussia.