Treaty of Riga
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The Peace of Riga, also known as the Treaty of Riga ( pl, Traktat Ryski), was signed in
Riga Riga (; lv, Rīga , liv, Rīgõ) is the capital and largest city of Latvia and is home to 605,802 inhabitants which is a third of Latvia's population. The city lies on the Gulf of Riga at the mouth of the Daugava river where it meets the ...
on 18 March 1921, among
Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populou ...
,
Soviet Russia The Russian Soviet Federative Socialist Republic, Russian SFSR or RSFSR ( rus, Российская Советская Федеративная Социалистическая Республика, Rossíyskaya Sovétskaya Federatívnaya Soci ...
(acting also on behalf of
Soviet Belarus The Byelorussian Soviet Socialist Republic (BSSR, or Byelorussian SSR; be, Беларуская Савецкая Сацыялістычная Рэспубліка, Bielaruskaja Savieckaja Sacyjalistyčnaja Respublika; russian: Белор ...
) and
Soviet Ukraine The Ukrainian Soviet Socialist Republic ( uk, Украї́нська Радя́нська Соціалісти́чна Респу́бліка, ; russian: Украи́нская Сове́тская Социалисти́ческая Респ ...
. The treaty ended the
Polish–Soviet War The Polish–Soviet War (Polish–Bolshevik War, Polish–Soviet War, Polish–Russian War 1919–1921) * russian: Советско-польская война (''Sovetsko-polskaya voyna'', Soviet-Polish War), Польский фронт (' ...
. The Soviet-Polish borders established by the treaty remained in force until
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
. They were later redrawn during the
Tehran Conference The Tehran Conference ( codenamed Eureka) was a strategy meeting of Joseph Stalin, Franklin Roosevelt, and Winston Churchill from 28 November to 1 December 1943, after the Anglo-Soviet invasion of Iran. It was held in the Soviet Union's embass ...
,
Yalta Conference The Yalta Conference (codenamed Argonaut), also known as the Crimea Conference, held 4–11 February 1945, was the World War II meeting of the heads of government of the United States, the United Kingdom, and the Soviet Union to discuss the post ...
and
Potsdam Conference The Potsdam Conference (german: Potsdamer Konferenz) was held at Potsdam in the Soviet occupation zone from July 17 to August 2, 1945, to allow the three leading Allies to plan the postwar peace, while avoiding the mistakes of the Paris P ...
.


Background

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
removed former imperial borders across Europe. Following the
Russian Revolution The Russian Revolution was a period of political and social revolution that took place in the former Russian Empire which began during the First World War. This period saw Russia abolish its monarchy and adopt a socialist form of government ...
which had renounced Tsarist claims to
Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populou ...
, as well as the
Central Powers The Central Powers, also known as the Central Empires,german: Mittelmächte; hu, Központi hatalmak; tr, İttifak Devletleri / ; bg, Централни сили, translit=Tsentralni sili was one of the two main coalitions that fought in W ...
provisions for
Congress Poland Congress Poland, Congress Kingdom of Poland, or Russian Poland, formally known as the Kingdom of Poland, was a polity created in 1815 by the Congress of Vienna as a semi-autonomous Polish state, a successor to Napoleon's Duchy of Warsaw. I ...
in the March 1918
Treaty of Brest-Litovsk The Treaty of Brest-Litovsk (also known as the Treaty of Brest in Russia) was a separate peace treaty signed on 3 March 1918 between Russia and the Central Powers ( Germany, Austria-Hungary, Bulgaria, and the Ottoman Empire), that ended Russi ...
,
The Great War World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
had ended with the collapse of the Central Powers. The
Treaty of Versailles The Treaty of Versailles (french: Traité de Versailles; german: Versailler Vertrag, ) was the most important of the peace treaties of World War I. It ended the state of war between Germany and the Allied Powers. It was signed on 28 June 1 ...
had re-established Poland's independence after a century and a half of being divided by three empires. The
Russian Civil War {{Infobox military conflict , conflict = Russian Civil War , partof = the Russian Revolution and the aftermath of World War I , image = , caption = Clockwise from top left: {{flatlist, *Soldiers ...
presented an opportunity for Poland, under the leadership of
Józef Piłsudski Józef Klemens Piłsudski (; 5 December 1867 – 12 May 1935) was a Polish statesman who served as the Naczelnik państwa, Chief of State (1918–1922) and Marshal of Poland, First Marshal of Second Polish Republic, Poland (from 1920). He was ...
, to regain parts of the territories of the former
Polish–Lithuanian Commonwealth The Polish–Lithuanian Commonwealth, formally known as the Kingdom of Poland and the Grand Duchy of Lithuania, and, after 1791, as the Commonwealth of Poland, was a bi-confederal state, sometimes called a federation, of Crown of the Kingdom of ...
that had been incorporated into the
Russian Empire The Russian Empire was an empire and the final period of the Russian monarchy from 1721 to 1917, ruling across large parts of Eurasia. It succeeded the Tsardom of Russia following the Treaty of Nystad, which ended the Great Northern War ...
during the Partitions of Poland–Lithuania. In 1920, Piłsudski's initially successful military offensive into Ukraine, whose aim was to establish an independent Ukraine in alliance with Poland, was met with a Soviet counter-offensive into central Poland. Poland was seen by the Soviets, who intended to extend the
revolution In political science, a revolution (Latin: ''revolutio'', "a turn around") is a fundamental and relatively sudden change in political power and political organization which occurs when the population revolts against the government, typically due ...
westwards, as a land bridge to
Western Europe Western Europe is the western region of Europe. The region's countries and territories vary depending on context. The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the ancient Mediterranean ...
. The
Polish–Soviet War The Polish–Soviet War (Polish–Bolshevik War, Polish–Soviet War, Polish–Russian War 1919–1921) * russian: Советско-польская война (''Sovetsko-polskaya voyna'', Soviet-Polish War), Польский фронт (' ...
culminated in the Battle of Warsaw, won by the Poles. Further military setbacks persuaded Soviet Russia to enter into peace treaty negotiations.THE REBIRTH OF POLAND
University of Kansas, lecture notes by Professor Anna M. Cienciala, 2004. Last accessed on 2 June 2006.
This was a relief for the government of Poland, a country heavily damaged and exhausted by the war, who also wanted to conclude peace talks. Piłsudski and his supporters, however, having failed in their quest, opposed the peace process.


Negotiations

Peace talks began in
Minsk Minsk ( be, Мінск ; russian: Минск) is the capital and the largest city of Belarus, located on the Svislach (Berezina), Svislach and the now subterranean Nyamiha, Niamiha rivers. As the capital, Minsk has a special administrative stat ...
on 17 August 1920, but the talks were moved to Riga, and resumed on 21 September. The Soviets proposed two solutions, the first on 21 September and the second on 28 September. The Polish delegation made a counter-offer on 2 October. Three days later the Soviets offered amendments to the Polish offer, which Poland accepted. An
armistice An armistice is a formal agreement of warring parties to stop fighting. It is not necessarily the end of a war, as it may constitute only a cessation of hostilities while an attempt is made to negotiate a lasting peace. It is derived from the ...
was signed on 12 October and went into effect on 18 October 1920. The chief negotiators were Jan Dąbski for Poland and Adolph Joffe for the
Russian Soviet Federative Socialist Republic The Russian Soviet Federative Socialist Republic, Russian SFSR or RSFSR ( rus, Российская Советская Федеративная Социалистическая Республика, Rossíyskaya Sovétskaya Federatívnaya Soci ...
. The Soviet side insisted, successfully, on excluding non-communist Ukrainian representatives from the negotiations. The Soviets' military setbacks made their delegation offer Poland substantial territorial concessions in the contested border areas. However, to many observers, it looked as though the Polish side conducted the Riga talks as if Poland had lost the war. The Polish delegation was dominated by members of the National Democrats, who were Piłsudski's political opponents. The National Democrats did not want non-Polish minorities in the reborn Polish state to constitute more than one-third of the overall population, therefore, prepared to accept a Polish-Soviet border substantially to the west of what was being offered by the Soviets even though it would leave hundreds of thousands of ethnic Poles on the Soviet side of the border. That decision was also motivated by political objectives. The National Democrats' base of public support was among Poles in central and western Poland. In the east of the country and in the disputed borderlands, support for the National Democrats was greatly outweighed by support for Piłsudski, and in the countryside, outside the cities, Poles were outnumbered by Ukrainians or Belarusians in those areas. A border too far to the east would thus be against not only the National Democrats' ideological objective of minimising the minority population of Poland but also their electoral prospects. Warweary public opinion in Poland also favoured an end to the negotiations, and both sides remained under pressure from the
League of Nations The League of Nations (french: link=no, Société des Nations ) was the first worldwide intergovernmental organisation whose principal mission was to maintain world peace. It was founded on 10 January 1920 by the Paris Peace Conference th ...
to reach a deal. A special parliamentary delegation, consisting of six members of the Polish
Sejm The Sejm (English: , Polish: ), officially known as the Sejm of the Republic of Poland ( Polish: ''Sejm Rzeczypospolitej Polskiej''), is the lower house of the bicameral parliament of Poland. The Sejm has been the highest governing body of ...
, held a vote on whether to accept the Soviets' far-reaching concessions, which would have left Minsk on the Polish side of the border. Pressured by the National Democrat ideologue, Stanisław Grabski, the 100 km of extra territory was rejected, a victory for the nationalist doctrine and a stark defeat for Piłsudski's
federalism Federalism is a combined or compound mode of government that combines a general government (the central or "federal" government) with regional governments ( provincial, state, cantonal, territorial, or other sub-unit governments) in a single ...
. Regardless, the peace negotiations dragged on for months because of Soviet reluctance to sign. However, the matter became more urgent for the Soviet leadership, which had to deal with increased internal unrest towards the end of 1920, such as the Tambov Rebellion and later the
Kronstadt rebellion The Kronstadt rebellion ( rus, Кронштадтское восстание, Kronshtadtskoye vosstaniye) was a 1921 insurrection of Soviet sailors and civilians against the Bolshevik government in the Russian SFSR port city of Kronstadt. Loc ...
against the Soviet authorities. As a result,
Vladimir Lenin Vladimir Ilyich Ulyanov. ( 1870 – 21 January 1924), better known as Vladimir Lenin,. was a Russian revolutionary, politician, and political theorist. He served as the first and founding head of government of Soviet Russia from 1917 to 1 ...
ordered the Soviet plenipotentiaries to finalise the peace treaty with Poland. The Peace of Riga, signed on 18 March 1921, partitioned the disputed territories in
Belarus Belarus,, , ; alternatively and formerly known as Byelorussia (from Russian ). officially the Republic of Belarus,; rus, Республика Беларусь, Respublika Belarus. is a landlocked country in Eastern Europe. It is bordered by ...
and
Ukraine Ukraine ( uk, Україна, Ukraïna, ) is a country in Eastern Europe. It is the second-largest European country after Russia, which it borders to the east and northeast. Ukraine covers approximately . Prior to the ongoing Russian inva ...
between Poland and Russia and ended the conflict.


Terms

The Treaty consisted of 26 articles. Poland was to receive monetary compensation (30 million
rubles The ruble (American English) or rouble (Commonwealth English) (; rus, рубль, p=rublʲ) is the currency unit of Belarus and Russia. Historically, it was the currency of the Russian Empire and of the Soviet Union. , currencies named ''rub ...
in gold) for its economic input into the
Russian Empire The Russian Empire was an empire and the final period of the Russian monarchy from 1721 to 1917, ruling across large parts of Eurasia. It succeeded the Tsardom of Russia following the Treaty of Nystad, which ended the Great Northern War ...
during the
Partitions of Poland The Partitions of Poland were three partitions of the Polish–Lithuanian Commonwealth that took place toward the end of the 18th century and ended the existence of the state, resulting in the elimination of sovereign Poland and Lithuania for 12 ...
. Under Article 14 Poland was also to receive railway materials (locomotives, rolling stock, etc.) with a value of 29 million gold roubles. Russia was to surrender works of art and other Polish national treasures acquired from Polish territories after 1772 (such as the Jagiellonian tapestries and the Załuski Library). Both sides renounced claims to war compensation. Article 3 stipulated that border issues between Poland and
Lithuania Lithuania (; lt, Lietuva ), officially the Republic of Lithuania ( lt, Lietuvos Respublika, links=no ), is a country in the Baltic region of Europe. It is one of three Baltic states and lies on the eastern shore of the Baltic Sea. Lithuania ...
would be settled by those states. Article 6 created citizenship options for persons on either side of the new border. Article 7 consisted of a mutual guarantee that all nationalities would be permitted "free intellectual development, the use of their national language, and the exercise of their religion." In the treaty, it was agreed that Poland would refuse to form federations with Lithuania, Belarus and Ukraine.


Aftermath

The Allied Powers were initially reluctant to recognise the treaty, which had been concluded without their participation. Their postwar conferences had supported the
Curzon Line The Curzon Line was a proposed demarcation line between the Second Polish Republic and the Soviet Union, two new states emerging after World War I. It was first proposed by The 1st Earl Curzon of Kedleston, the British Foreign Secretary, ...
as the Polish-Russian border, and Poland's territorial gains in the treaty lay about 250 km east of that line. French support led to its recognition in March 1923 by France, the United Kingdom, Italy and Japan, followed by the United States in April. In Poland, the Peace of Riga was met with criticism from the very beginning. Some characterised the treaty as short-sighted and argued that much of what Poland had gained during the Polish-Soviet war was lost during the peace negotiations.
Józef Piłsudski Józef Klemens Piłsudski (; 5 December 1867 – 12 May 1935) was a Polish statesman who served as the Naczelnik państwa, Chief of State (1918–1922) and Marshal of Poland, First Marshal of Second Polish Republic, Poland (from 1920). He was ...
had participated in the Riga negotiations only as an observer and called the resulting treaty "an act of cowardice". (First edition: New York, St. Martin's Press, inc., 1972.) Piłsudski felt the agreement was a shameless and short-sighted political calculation, with Poland abandoning its Ukrainian allies. On 15 May 1921, he apologised to Ukrainian soldiers during his visit to the internment camp at
Kalisz (The oldest city of Poland) , image_skyline = , image_caption = ''Top:'' Town Hall, Former "Calisia" Piano Factory''Middle:'' Courthouse, "Gołębnik" tenement''Bottom:'' Aerial view of the Kalisz Old Town , image_flag = POL Kalisz flag.svg ...
. The treaty substantially contributed to the failure of his plan to create a Polish-led Intermarium federation of
Eastern Europe Eastern Europe is a subregion of the European continent. As a largely ambiguous term, it has a wide range of geopolitical, geographical, ethnic, cultural, and socio-economic connotations. The vast majority of the region is covered by Russia, whi ...
, as portions of the territory that had been proposed for the federation were ceded to the Soviets. Lenin also considered the treaty unsatisfactory, as it forced him to put aside his plans for exporting the Soviet revolution to the West. The Belarusian and Ukrainian independence movements saw the treaty as a setback. Four million Ukrainians and over a million Belarusians lived within areas ceded to Poland. In one estimate, only 15% of the population was ethnically Polish. The
Ukrainian People's Republic The Ukrainian People's Republic (UPR), or Ukrainian National Republic (UNR), was a country in Eastern Europe that existed between 1917 and 1920. It was declared following the February Revolution in Russia by the First Universal. In March 1 ...
, led by
Symon Petliura Symon Vasylyovych Petliura ( uk, Си́мон Васи́льович Петлю́ра; – May 25, 1926) was a Ukrainian politician and journalist. He became the Supreme Commander of the Ukrainian Army and the President of the Ukrainian Peop ...
, had been allied with Poland under the Treaty of Warsaw, which was abrogated by the Peace of Riga. The new treaty violated Poland's military alliance with the UPR, which had explicitly prohibited a separate peace. Doing so worsened relations between Poland and the Ukrainians who had supported Petliura. The supporters felt that Ukraine had been betrayed by its Polish ally, which would be exploited by the Organization of Ukrainian Nationalists and contribute to the growing tensions and eventual anti-Polish massacres in the 1930s and the 1940s. By the end of 1921, most Poland-allied Ukrainian, Belarusian and White Russian forces had been annihilated by Soviet forces or had crossed the border into Poland and laid down their arms. According to the Belarusian historian Andrew Savchenko, Poland's new eastern border was "military indefensible and economically unviable" and a source of growing ethnic tensions, as the resulting minorities in Poland were too large to be ignored or assimilated and too small to win their desired autonomy.


Further consequences

While the Peace of Riga led to a two-decade stabilisation of Soviet-Polish relations, conflict was renewed with the
Soviet invasion of Poland The Soviet invasion of Poland was a military operation by the Soviet Union without a formal declaration of war. On 17 September 1939, the Soviet Union invaded Poland from the east, 16 days after Nazi Germany invaded Poland from the west. Subs ...
during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
. The treaty was subsequently overridden after a decision by war's Allied powers to change Poland's borders once again and transfer the populations. In the view of some foreign observers, the treaty's incorporation of significant minority populations into Poland led to seemingly insurmountable challenges, because the newly formed organizations such as OUN engaged in terror and sabotage actions across ethnically mixed areas to inflame conflict in the region. Nevertheless, many groups representing national minorities welcomed Piłsudski's return to power in 1926 providing opportunities to play a role in the Polish government. The populations separated from Poland by the new Polish-Soviet border experienced a different fate from their fellow citizens. Ethnic Poles left within Soviet borders were subjected to discrimination and property confiscation.J. M. Kupczak "Stosunek władz bolszewickich do polskiej ludności na Ukrainie (1921–1939)Wrocławskie Studia Wschodnie 1 (1997) Wydawnictwo Uniwersytetu Wrocławskiego , 1997 page 47–62" IPN Bulletin 11(34) 2003 At least 111,000 were summarily executed in the NKVD operation in 1937/38, preceding other ethnic repression campaigns perpetrated during World War II, while others were exiled to different regions of the Soviet Union. Belarusians and Ukrainians, having failed to create their own states, were subjects of repression in the Soviet Union, and even extermination e.g. during the
Holodomor The Holodomor ( uk, Голодомо́р, Holodomor, ; derived from uk, морити голодом, lit=to kill by starvation, translit=moryty holodom, label=none), also known as the Terror-Famine or the Great Famine, was a man-made famin ...
.Jones, Adam (2010). Genocide: A Comprehensive Introduction. Taylor & Francis. p. 194. . Belarusians and Ukrainians living on the Polish side of the border were subjected to
Polonization Polonization (or Polonisation; pl, polonizacja)In Polish historiography, particularly pre-WWII (e.g., L. Wasilewski. As noted in Смалянчук А. Ф. (Smalyanchuk 2001) Паміж краёвасцю і нацыянальнай ідэя ...
; which contributed to the rise of Ukrainian nationalist organisations and the adoption of
terrorist Terrorism, in its broadest sense, is the use of criminal violence to provoke a state of terror or fear, mostly with the intention to achieve political or religious aims. The term is used in this regard primarily to refer to intentional violen ...
tactics by Ukrainian extremists. The Soviet Union, although thwarted in 1921, would see its sphere of influence expand as a result of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
. After the Soviet Union established its control over the
People's Republic of Poland The Polish People's Republic ( pl, Polska Rzeczpospolita Ludowa, PRL) was a country in Central Europe that existed from 1947 to 1989 as the predecessor of the modern Republic of Poland. With a population of approximately 37.9 million ne ...
, the Polish-Soviet border was moved westwards in 1945 to roughly coincide with the
Curzon Line The Curzon Line was a proposed demarcation line between the Second Polish Republic and the Soviet Union, two new states emerging after World War I. It was first proposed by The 1st Earl Curzon of Kedleston, the British Foreign Secretary, ...
. This shift was accompanied by large population transfers which led to the expulsion of the Poles living east of the new border, and also moved most of the Ukrainian minority remaining in Poland to the former German territories that were ceded to Poland in compensation. The unified Belarusian and Ukrainian territories were fully incorporated into the USSR. However, in 1989, Poland would regain its full sovereignty, and soon afterwards, with the
fall of the Soviet Union The dissolution of the Soviet Union, also negatively connoted as rus, Разва́л Сове́тского Сою́за, r=Razvál Sovétskogo Soyúza, ''Ruining of the Soviet Union''. was the process of internal disintegration within the Sov ...
,
Belarus Belarus,, , ; alternatively and formerly known as Byelorussia (from Russian ). officially the Republic of Belarus,; rus, Республика Беларусь, Respublika Belarus. is a landlocked country in Eastern Europe. It is bordered by ...
and
Ukraine Ukraine ( uk, Україна, Ukraïna, ) is a country in Eastern Europe. It is the second-largest European country after Russia, which it borders to the east and northeast. Ukraine covers approximately . Prior to the ongoing Russian inva ...
would go on to become independent nations.


See also

* Polish minority in the Soviet Union * Belarusian minority in Poland *
Ukrainian minority in Poland Ukrainians in Poland have various legal statuses: ethnic minority, temporary and permanent residents, and refugees. According to the Polish census of 2011, the Ukrainian minority in Poland was composed of approximately 51,000 people (including ...
*
Byelorussian Soviet Socialist Republic The Byelorussian Soviet Socialist Republic (BSSR, or Byelorussian SSR; be, Беларуская Савецкая Сацыялістычная Рэспубліка, Bielaruskaja Savieckaja Sacyjalistyčnaja Respublika; russian: Белор ...
*
Ukrainian Soviet Socialist Republic The Ukrainian Soviet Socialist Republic ( uk, Украї́нська Радя́нська Соціалісти́чна Респу́бліка, ; russian: Украи́нская Сове́тская Социалисти́ческая Респ ...
* Aftermath of the Polish-Soviet War * Polish Operation of the NKVD (1937–38) * Latvian–Soviet Peace Treaty * Soviet–Lithuanian Peace Treaty *
Treaty of Tartu (Estonia–Russia) The Treaty of Tartu ( et, Tartu rahu, lit=Tartu peace) is a peace treaty that was signed in Tartu on 2 February 1920 between the Republic of Estonia and Soviet Russia, ending the 1918–1920 Estonian War of Independence. In the treaty, Bolshevik ...
*
Treaty of Tartu (Finland–Russia) , image = Treaty-of-Tartu.png , image_width = 150px , caption = The Finland–Russia border as decided in the Treaty of Tartu. Petsamo (red) became part of Finland, while Repola and Porajärvi (green) were hand ...


Notes


Further reading

* Dąbrowski, Stanisław. "The Peace Treaty of Riga." ''The Polish Review'' (1960) 5#1: 3-34
Online
*
Davies, Norman Ivor Norman Richard Davies (born 8 June 1939) is a Welsh-Polish historian, known for his publications on the history of Europe, Poland and the United Kingdom. He has a special interest in Central and Eastern Europe and is UNESCO Professo ...
, ''White Eagle, Red Star: the Polish-Soviet War, 1919–20'', Pimlico, 2003, . (First edition: New York, St. Martin's Press, inc., 1972.) * Materski, Wojciech. "The Second Polish Republic in Soviet Foreign Policy (1918-1939)." ''Polish Review'' 45.3 (2000): 331-345
online
* ''Traktat ryski 1921 roku po 75 latach'', Wydawnictwo Uniwersytetu Mikołaja Kopernika, Toruń 1998, (Chapter summaries in English)

Dziedzictwo.polska.pl {{Authority control Riga, Peace of Polish–Soviet War 1921 in Ukraine 1921 in Belarus 1921 in Latvia Treaties concluded in 1921 Treaties entered into force in 1921 Treaties of the Second Polish Republic Treaties of the Russian Soviet Federative Socialist Republic Treaties of the Ukrainian Soviet Socialist Republic Poland–Russia relations Poland–Ukraine military relations 20th century in Riga Peace treaties of the Soviet Union March 1921 events