The Border Agreement between Poland and the USSR of 16 August 1945 established the borders between theSoviet Union (USSR) and thePeople's Republic of Poland. It was signed by theProvisional Government of National Unity (Tymczasowy Rząd Jedności Narodowej) formed by thePolish communists. According to the treaty, Poland officially accepted theceding its pre-war Eastern territory to the USSR (Kresy) which was decided earlierin Yalta already. Some of the territory along theCurzon line, established by Stalin during the course of the war, was returned to Poland. The treaty also recognised the division of the former GermanEast Prussia and ultimately approved the finaliseddelimitation line between the Soviet Union and Poland: from theBaltic Sea, to the border tripoint withCzechoslovakia in theCarpathians.[1][2][3] The agreement entered into force on 5 February 1946.[4]
Prior to theFirst World War, within theRussian Empire Polish territories were administered by aVistula Land, whose eastern frontier roughly mirrored the ethnic border between thePolish people on the west, and theUkrainians andBelarusians (then referred to asLittle and White Russians respectively) on the east. InAustrian Galicia there was no administrative border which marked the ethnic one between the Polish and the Galician Ukrainians (Ruthenians). Ukrainian territories were also heavily infiltrated by Polish increpancies.
During theFirst World War, theRussian Civil, thePolish-Soviet andPolish-Ukrainian wars, the territory passed hands several times, and each of the controlling powers tried to create its own administration on the region. During the conflict, theSupreme War Council tried several times to intervene and create an agreeable border between theSecond Polish Republic andBolshevik Russia; the most notable outcome was the border presented by the British Foreign SecretaryGeorge Curzon, after whom theproposed line was named. The line mostly followed the 19th century border between theVistula Land, but also extended further south and portioned Galicia along the rough ethnic border between Poles and Ukrainians.
Though accepted by the Bolshevik government, the line was ignored by Poland, and after thePolish-Soviet War's conclusion, on theTreaty of Riga, Bolshevik Russia recognised a new border almost 250 km east of the Curzon Line. The border was recognised by theLeague of Nations in 1923, and confirmed by numerous Polish-Soviet treaties and delimited in due course.
TheMolotov–Ribbentrop Pact of August 1939 provided for the partition of theSecond Polish Republic between theUSSR andNazi Germany. Following the corresponding invasions, a new border was drawn up, though based on theCurzon Line, deviated west of it in several regions. Most notably, was theBelastok Region, that was added to theByelorussian Soviet Socialist Republic, although most of the region was populated by Poles.[citation needed]
After Germany's invasion of the USSR, the territory in question was also re-partitioned by the Nazis. Ukraine and Belarus were administered by the occupationOstland andReichskommissariat Ukraine Reichskommissariats. Galician territory east of the 1939 border and the Belastok Region plus adjacent territory to the east of this were transformed respectively into theDistrikt Galizien andBezirk Bialystok, and subjugated directly to theReich.
Following the Soviet Union's liberation of Ukraine and Belarus, in 1943/1944 theTehran Conference andYalta Conference discussed upon the future of the Polish-Soviet borders, and the Allied leaders recognised the Soviet right to the territory east of the 1939 border. However, after the liberation of Western Ukraine and Belarus in summer of 1944, a Polish committee formed in the town ofSapotskin sent a letter to Moscow asking that they remain part of Poland. Stalin agreed, and on 29 September, administration of 17 (of the 23) districts of Belastok Region (including the city ofBiałystok) and an additional three (Siemiatycze,Hajnówka andKleszczele) of theBrest Region were passed to thePolish Committee of National Liberation from the BSSR.
In October 1944 these were joined by a further transfer ofLubaczów,Horyniec,Laszki,Uhnów andSieniawa raions of theLviv Oblast from theUkrainian Soviet Socialist Republic. In March 1945, an additional batch of land, theBieszczady,Lesko, and most of Przemyśl raions (including Przemyśl city) were transferred to Poland from theDrohobych Oblast of Ukraine to the nowProvisional Government of the Republic of Poland.
Soon afterwards World War II finished, and as the Provisional Government continued to transfer administration from military to civil bodies, it also finalised its new borders with its neighbors, and in particular, the Soviet Union. Soviet claims, which became the main problem preventing cooperation between the Polish government in London and Moscow during the war, were then accepted by PKWN activists in July 1944. Their consent to the Curzon line signed on 27 July 1944 (Relinquishing half of theBiałowieża Forest was Stalin's only concession, and representatives of thePolish Committee of National Liberation were afraid to mention the return of Lviv which became part of theUkrainian SSR) was a condition for sending these activists to Lublin and Chełm.
On 16 August 1945, the border agreement was officially signed byEdward Osóbka-Morawski, on behalf of theProvisional Government of National Unity andVyacheslav Molotov, the Soviet Minister of Foreign affairs. The exchange of ratified documents occurred on 5 February 1946 in Warsaw, and from that date the agreement was in force.
Although the treaty finalised the 1939 line, with the 1944/45 adjustments, the border would receive a few more alterations. On 15 May 1948, the raion ofMedyka was transferred from theDrohobych Oblast of Ukraine to theRepublic of Poland. And finally a1951 Polish–Soviet territorial exchange, saw Poland return its pre-1939 territory ofUstrzyki Dolne raion from theDrohobych Oblast, and instead it passed the USSR part of theLublin Voivodship, with the cities ofBelz,Uhniv,Chervonohrad andVaryazh, (all of which after the Nazi and Soviet Axis invasion of Poland in September 1939 became a part of Poland occupied by the USSR and was allocated to Ukraine in 1939 until 1941 when the Nazis invaded the Soviet Union. It was occupied again in 1944–1945 after the Soviet advance to Berlin). The border between Poland and Belarus, and Poland and Ukraine has remained the same since.
