Belarus' Western Territory: Poland's New Acquisition

Western Belarus is a historical region of modern-day Belarus which belonged to the Second Polish Republic during the interwar period. The region was invaded by the Soviet Union in 1939, and after World War II, most of Western Belarus was ceded to the Soviet Union, while some of it was given to the Polish People's Republic. The region has a complex history, with its borders and ownership changing hands multiple times over the last century. Today, it constitutes the west of modern Belarus, with a significant Polish minority.

The Polish-Soviet War (1918-1921)

After the Armistice of 11 November 1918, Vladimir Lenin's Soviet Russia annulled the Treaty of Brest-Litovsk and moved forces westward to reclaim the Ober Ost regions abandoned by the Germans. Lenin viewed the newly independent Poland as a critical route for spreading communist revolutions into Europe. Meanwhile, Polish leaders, including Józef Piłsudski, aimed to restore Poland’s pre-1772 borders and secure the country's position in the region.

The war began on 14 February 1919, with Polish forces occupying much of present-day Lithuania and Belarus, emerging victorious in the Polish–Ukrainian War. However, Soviet forces regained strength after their victories in the Russian Civil War. In April 1920, Piłsudski launched the Kiev offensive with the goal of securing favourable borders for Poland. On 7 May, Polish and allied Ukrainian forces captured Kiev, though Soviet armies in the area were not decisively defeated.

In response, the Soviet Red Army launched a successful counteroffensive in June 1920. By August, Soviet troops had pushed Polish forces back to Warsaw. However, at the decisive Battle of Warsaw (1920), Polish forces achieved an unexpected victory between 12 and 25 August 1920, turning the tide of the war. This battle, often referred to as the "Miracle on the Vistula," is considered one of the most significant military triumphs in Polish history.

The war ended with a ceasefire on 18 October 1920, and peace negotiations led to the Peace of Riga, signed on 18 March 1921. The treaty divided disputed territories between Poland and Soviet Russia, with Poland securing parts of modern-day Ukraine and Belarus. The war resulted in the official recognition of the Ukrainian Soviet Socialist Republic and the Byelorussian Soviet Socialist Republic as Soviet states, undermining Piłsudski’s ambitions for an Intermarium federation led by Poland. Despite this, Poland's success at the Battle of Warsaw cemented its position as a significant player in Eastern European geopolitics in the interwar period.

The Second Polish Republic

The Second Republic was a multiethnic country, with the census of 1921 showing that 30.8% of the population consisted of ethnic minorities. Almost a third of the population came from minority groups, including 13.9% Ukrainians, 10% Ashkenazi Jews, 3.1% Belarusians, 2.3% Germans, and 3.4% Czechs and Lithuanians. The official languages of the Second Republic were Polish, Ukrainian, Belarusian, and Lithuanian.

The Second Republic maintained moderate economic development, with the cultural hubs of Warsaw, Kraków, Poznań, Wilno, and Lwów becoming major European cities and sites of internationally acclaimed universities and institutions of higher education. The Second Republic had a large army of 270,000 soldiers on active duty, with another 700,000 serving in the reserves. The training of the Polish Army was thorough, with competent non-commissioned officers and constant training for senior and junior officers.

The Second Republic faced several political and socioeconomic difficulties, including the issue of minorities, the search for a constitutional model that reconciled Polish strivings for liberty with the need for a strong government, and the Great Depression of the 1930s, which had a crippling effect on the economy. Interwar politics centred on Marshal Józef Piłsudski, who came out of retirement in 1926 and staged an armed demonstration to force President Stanisław Wojciechowski to dismiss the government. Piłsudski's regime, called Sanacja in Polish, was authoritarian, with Piłsudski worshipped by his supporters and hated by his opponents.

The Second Republic's existence ended with the German invasion of Poland on 1 September 1939, which marked the beginning of World War II. The Poles fought alone against the Wehrmacht's overwhelming might and were doomed. On 17 September 1939, the Red Army invaded Poland from the east, and on 28 September, Hitler and Stalin agreed on a final partition, with the Soviets taking more than half of the country. The Holocaust claimed the lives of about three million Polish Jews, and thousands of non-Jewish Poles were also executed by the Nazis.

The Soviet invasion of Poland in 1939

On September 17, 1939, the Soviet Union invaded Poland from the east, 16 days after Nazi Germany invaded from the west. The Soviet invasion was a direct result of the Molotov-Ribbentrop Pact, signed between Nazi Germany and the Soviet Union on August 23, 1939. This non-aggression pact contained a secret protocol that divided Poland and other parts of Northern and Eastern Europe into "spheres of influence" of the two powers.

The Soviet invasion of Poland was a military conflict without a formal declaration of war. The Red Army, which vastly outnumbered the Polish defenders, achieved its targets, encountering only limited resistance. Some 320,000 Poles were made prisoners of war. The campaign of mass persecution in the newly acquired areas began immediately. In November 1939, the Soviet government annexed the entire Polish territory under its control. Some 13.5 million Polish citizens who fell under military occupation were made Soviet subjects following show elections, which were used to legitimise the use of force.

The Soviet invasion of Poland was also the result of the desire to reunite Western Belorussia and Ukraine. Soon after the invasion, the area of Western Belorussia was formally annexed into the Belarusian Soviet Socialist Republic (BSSR). The Soviet occupational administration held elections on October 22, 1939, less than two weeks after the invasion. Citizens were threatened with deportation to Siberia if they did not comply. The ballot envelopes were numbered and handed over sealed. The referendum was rigged, and the unification voting in the People's Assembly of Western Belorussia was not successful until the second attempt, when 10 Lithuanians, who initially voted against unification, changed their vote.

On October 30, the People's Assembly session affirmed the Soviet decision to join the BSSR with the USSR. From then on, all citizens of Poland would find themselves living in the BSSR as Soviet subjects, without the recognition of their Polish citizenship. The Soviet propaganda portrayed the invasion as the "reunion of Western Belorussia and Ukraine". Many ethnic Belarusians and Jews welcomed the unification, but wealthy groups changed their attitude after experiencing the Soviet system firsthand.

The Soviets quickly began confiscating and redistributing all private and state-owned property. During the two years following the annexation, the Soviets arrested approximately 100,000 Polish citizens across Kresy. Due to a lack of access to secret Soviet archives, estimates of the number of Polish citizens deported to Siberia and the total number who perished under Soviet rule remained guesswork for decades after the war. In August 2009, the Polish Institute of National Remembrance announced that research estimates on the number of people deported to Siberia and those who perished under Soviet rule amounted to around 150,000 Polish citizens.

The population exchange between Poland and Soviet Belarus after World War II

The population exchange between Poland and Soviet Belarus at the end of World War II was based on an agreement signed on 9 September 1944 by the Byelorussian SSR with the newly-formed Polish Committee of National Liberation (PKWN). The agreement stipulated the resettlement of ethnic Belarusians from Poland to Belarus and of ethnic Poles and Jews who had Polish citizenship before 17 September 1939 (the date of the Soviet invasion of Poland) from Belarus to Poland. This was in accordance with the resolutions of the Yalta and Tehran conferences and the plans for the new Belarus-Poland border.

The population exchange was part of a broader pattern of population transfers that took place in Central and Eastern Europe following World War II, as nations sought ethnic consolidation. The new border between post-war Poland and the Soviet Union, ratified at the Yalta Conference, followed the Curzon Line. This resulted in the transfer of close to half a million ethnic Ukrainians and about 1.1 million Poles and Polish Jews.

In the case of Belarus and Poland, the transfer of populations was not as straightforward as in the case of Ukraine and Poland. In Belarus, communist officials did not actively support the deportation of Poles. Belarusian officials obstructed communication between Polish activists and tuteishians – people who were undecided as to whether they considered themselves Polish or Belarusian. Rural populations without official identity documents were denied the "right" of repatriation on the basis that they did not have documents stating they were Polish citizens.

In contrast, Polish officials attempted to repatriate as many people as possible. As a result, it is estimated that about 150,000 to 250,000 people were deported from Belarus, while similar numbers were registered as Poles but forced to remain in Belarus or denied registration as Poles.

In response, Poland adopted a similar approach towards the Belarusian population of the Białystok Voivodeship, which was partially retained by Poland after World War II. Poland sought to retain some of the Belarusian people.

According to the agreement, the transfer of populations was completed by July 1946. Of the 160,000 ethnic Belarusians, about 80,000 (according to Jasiak) or 38,000 (according to Mironowicz) were deported to the Byelorussian SSR and resettled there.

Initially, residents of the westernmost parts of Western Belarus were hesitant to register for resettlement, as they hoped that these areas would remain in Poland. However, as the situation clarified, public opinion, including the underground, adopted the opposite stance.

The population exchange between Poland and Soviet Belarus was part of a broader set of agreements known as the Republican Agreements, which also included similar agreements with the Ukrainian SSR and the Lithuanian SSR.

The current border between Poland and Belarus

The border between Poland and Belarus has changed multiple times throughout history. In the interwar period, Western Belarus belonged to the Second Polish Republic. Following the Soviet invasion of Poland in 1939, the northern part of the Polish Kresy macroregion, including Western Belarus, was annexed into the Byelorussian Soviet Socialist Republic. Five new Voblasts were created: Baranavichy, Belostok, Brest, Pinsk, and Vilyeyka. After World War II, the border between Poland and Belarus was finalised. In accordance with the Border Agreement between Poland and the USSR in 1945, 17 districts of Belastok Voblast of the BSSR, including the city of Białystok, and 3 districts of Brest Voblast were restored to Poland.

In recent years, the Poland-Belarus border has been the site of increased tensions and a migrant crisis. In August 2021, a wave of illegal immigrants started fleeing through Belarus to Poland, with Belarus being accused of orchestrating and supporting the crossings. Poland has reinforced the border and built a barrier to stop the crossings. In July 2023, Belarus announced joint military exercises with Wagner fighters near the border with Poland, and in May 2024, two Polish border guards were injured in an attack by migrants.

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