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The Sejny Uprising or Seinai Revolt ( pl, Powstanie sejneńskie, lt, Seinų sukilimas) refers to a Polish uprising against the Lithuanian authorities in August 1919 in the ethnically mixed area surrounding the town of
Sejny Sejny ( lt, Seinai) is a town in north-eastern Poland and the capital of Sejny County, in Podlaskie Voivodeship, close to the northern border with Lithuania and Belarus. It is located in the eastern part of the Suwałki Lake Area ( pl, Pojezier ...
( lt, Seinai). When German forces, which occupied the territory during
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, ...
, retreated from the area in May 1919, they turned over administration to the Lithuanians. Trying to prevent an armed conflict between Poland and Lithuania, the
Entente Entente, meaning a diplomatic "understanding", may refer to a number of agreements: History * Entente (alliance), a type of treaty or military alliance where the signatories promise to consult each other or to cooperate with each other in case o ...
drew a demarcation line, known as the Foch Line. The line assigned much of the disputed Suwałki (Suvalkai) Region to Poland and required the
Lithuanian Army The Lithuanian Armed Forces () are the military of Lithuania. The Lithuanian Armed Forces consist of the Lithuanian Land Forces, the Lithuanian Naval Force and the Lithuanian Air Force. In wartime, the Lithuanian State Border Guard Service ( ...
to retreat. While the Lithuanians retreated from some areas, they refused to leave Sejny (Seinai), because of its major Lithuanian population. Polish irregular forces began the uprising on August 23, 1919, and soon received support from the regular
Polish Army The Land Forces () are the land forces of the Polish Armed Forces. They currently contain some 62,000 active personnel and form many components of the European Union and NATO deployments around the world. Poland's recorded military history str ...
. After several military skirmishes, Polish forces secured Sejny and the Lithuanians retreated behind the Foch Line. The uprising did not solve the larger border conflict between Poland and Lithuania over the ethnically mixed
Suwałki Region Suwałki Region ( pl, Suwalszczyzna ; lt, Suvalkų kraštas, Suvalkija, russian: cувалкщина, german: Sudauen) is a small region around the city of Suwałki (known in Lithuanian as ''Suvalkai'') in northeastern Poland near the border wit ...
. Both sides complained about each other's repressive measures. The conflict intensified in 1920, causing military skirmishes of the
Polish–Lithuanian War The Polish–Lithuanian War (in Polish historiography, Polish–Lithuanian Conflict) was an undeclared war between newly-independent Lithuania and Poland following World War I, which happened mainly, but not only, in the Vilnius and Suwałki reg ...
. Sejny changed hands frequently until the
Suwałki Agreement The Suwałki Agreement, Treaty of Suvalkai, or Suwalki Treaty ( pl, Umowa suwalska, lt, Suvalkų sutartis) was an agreement signed in the town of Suwałki between Poland and Lithuania on October 7, 1920. It was registered in the '' League of ...
of October 1920, which left Sejny on the Polish side. The uprising undermined the plans of Polish leader
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 ...
who was planning a coup d'état in Lithuania to replace the Lithuanian government with a pro-Polish cabinet which would agree to a union with Poland (the proposed
Międzymorze Intermarium ( pl, Międzymorze, ) was a post-World War I geopolitical plan conceived by Józef Piłsudski to unite former Polish–Lithuanian Commonwealth lands within a single polity. The plan went through several iterations, some of which antic ...
federation). Because the Sejny Uprising had prompted the Lithuanian intelligence to intensify its investigations of Polish activities in Lithuania, they discovered plans for the coup and prevented it, arresting Polish sympathizers. These hostilities in Sejny further strained the
Polish–Lithuanian relations Polish–Lithuanian can refer to: * Polish–Lithuanian union (1385–1569) * Polish–Lithuanian Commonwealth (1569–1795) * Polish-Lithuanian identity as used to describe groups, families, or individuals with histories in the Polish–Lithuanian ...
. Eventually, Poland and Lithuania reached an agreement on a new border that left Sejny on the Polish side of the border. The Polish–Lithuanian border in the Suwałki Region has remained the same since then (with the exception of the
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 ...
period).


Background

During the ages, the lands surrounding the town of
Suwałki Suwałki ( lt, Suvalkai; yi, סואוואַלק) is a city in northeastern Poland with a population of 69,206 (2021). It is the capital of Suwałki County and one of the most important centers of commerce in the Podlaskie Voivodeship. Suwałki ...
were part of the
Grand Duchy of Lithuania The Grand Duchy of Lithuania was a European state that existed from the 13th century to 1795, when the territory was partitioned among the Russian Empire, the Kingdom of Prussia, and the Habsburg Empire of Austria. The state was founded by Lit ...
until 1795. Sejny itself was property of
Vilnius Vilnius ( , ; see also other names) is the capital and largest city of Lithuania, with a population of 592,389 (according to the state register) or 625,107 (according to the municipality of Vilnius). The population of Vilnius's functional u ...
' Dominican friars from 1603 until 1805. During the
Third Partition of the Polish-Lithuanian Commonwealth The Third Partition of Poland (1795) was the last in a series of the Partitions of Poland–Lithuania and the land of the Polish–Lithuanian Commonwealth among Prussia, the Habsburg monarchy, and the Russian Empire which effectively ended Polis ...
in 1795, the region became part of the
Kingdom of Prussia The Kingdom of Prussia (german: Königreich Preußen, ) constituted the German state of Prussia between 1701 and 1918. Marriott, J. A. R., and Charles Grant Robertson. ''The Evolution of Prussia, the Making of an Empire''. Rev. ed. Oxford: ...
as
New East Prussia New East Prussia (german: Neuostpreußen; pl, Prusy Nowowschodnie; lt, Naujieji Rytprūsiai) was a province of the Kingdom of Prussia from 1795 to 1807. It was created out of territory annexed in the Third Partition of the Polish–Lithuanian C ...
until 1807, from then until 1815, it was part of the
Duchy of Warsaw The Duchy of Warsaw ( pl, Księstwo Warszawskie, french: Duché de Varsovie, german: Herzogtum Warschau), also known as the Grand Duchy of Warsaw and Napoleonic Poland, was a French client state established by Napoleon Bonaparte in 1807, during ...
which Napoleon had created. For a century after the conclusion of the
Napoleonic Wars The Napoleonic Wars (1803–1815) were a series of major global conflicts pitting the French Empire and its allies, led by Napoleon I, against a fluctuating array of European states formed into various coalitions. It produced a period of Fren ...
, the town was in
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. It ...
, a part of the
Russian Empire The Russian Empire was an empire and the final period of the List of Russian monarchs, 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 th ...
. During
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, ...
, the region was captured by the German Empire, which intended to incorporate the area into its province of
East Prussia East Prussia ; german: Ostpreißen, label= Low Prussian; pl, Prusy Wschodnie; lt, Rytų Prūsija was a province of the Kingdom of Prussia from 1773 to 1829 and again from 1878 (with the Kingdom itself being part of the German Empire from 1 ...
. After the German defeat, the victorious
Entente Entente, meaning a diplomatic "understanding", may refer to a number of agreements: History * Entente (alliance), a type of treaty or military alliance where the signatories promise to consult each other or to cooperate with each other in case o ...
was willing to assign the territory to either the newly independent Poland or Lithuania. The future of the region was discussed at the
Paris Peace Conference Agreements and declarations resulting from meetings in Paris include: Listed by name Paris Accords may refer to: * Paris Accords, the agreements reached at the end of the London and Paris Conferences in 1954 concerning the post-war status of Germ ...
in January 1919. The Germans, whose former
Ober-Ost , short for ( "Supreme Commander of All German Forces in the East"), was both a high-ranking position in the armed forces of the German Empire as well as the name given to the occupied territories on the German section of the Eastern Front of ...
administration was preparing to evacuate, initially supported leaving the area to a Polish administration. However, as Poland was becoming an ally of
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan ar ...
, German support gradually shifted towards Lithuania. In July 1919, when the German troops began their slow retreat from the area, they delegated the administration to local Lithuanian authorities. Lithuanian officers and troops, who first arrived in the region in May, began to organize military units in the pre-war
Sejny county __NOTOC__ Sejny County ( pl, powiat sejneński) a unit of territorial administration and local government (powiat) in Podlaskie Voivodeship, in the extreme north-east of Poland, on the border with Lithuania and Belarus. It came into being on Janua ...
. According to Russian statistics from 1889, there were 57.8% Lithuanians, 19.1% Poles, and 3.5% Belarusians in the
Suwałki Governorate Suwałki Governorate (russian: Сувалкская губерния, pl, gubernia suwalska, lt, Suvalkų gubernija) was a governorate (administrative area) of Congress Poland ("Russian Poland") which had its seat in the city of Suwałki. It cove ...
. It is generally agreed that Lithuanians formed the majority of the population in the northern Suwałki Governorate, while Poles were concentrated in the south. But Lithuanian and Polish historians and political scientists continued to disagree over the location of the line that separated the areas of Lithuanian and Polish majorities. Lithuanians claimed that Sejny and the surrounding area were inhabited primarily by the Lithuanians, while the Poles claimed exactly the opposite. The German census of 1916 showed that 51% of Sejny population was Lithuanian.


Demarcation lines

In the
aftermath of World War I The aftermath of World War I saw drastic political, cultural, economic, and social change across Eurasia, Africa, and even in areas outside those that were directly involved. Four empires collapsed due to the war, old countries were abolished, ne ...
, the
Conference of Ambassadors The Conference of Ambassadors of the Principal Allied and Associated Powers was an inter-allied organization of the Entente in the period following the end of World War I. Formed in Paris in January 1920 it became a successor of the Supreme War C ...
drew the first
demarcation line {{Refimprove, date=January 2008 A political demarcation line is a geopolitical border, often agreed upon as part of an armistice or ceasefire. Africa * Moroccan Wall, delimiting the Moroccan-controlled part of Western Sahara from the Sahrawi ...
between Poland and Lithuania on June 18, 1919. The line satisfied no one, and Polish troops continued to advance deeper into the Lithuanian-controlled territory. These attacks coincided with the signing of 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 ...
on June 28, which eliminated any danger from Germany. Attempting to halt further hostilities,
Marshal of France Marshal of France (french: Maréchal de France, plural ') is a French military distinction, rather than a military rank, that is awarded to generals for exceptional achievements. The title has been awarded since 1185, though briefly abolished ( ...
Ferdinand Foch Ferdinand Foch ( , ; 2 October 1851 – 20 March 1929) was a French general and military theorist who served as the Supreme Allied Commander during the First World War. An aggressive, even reckless commander at the First Marne, Flanders and A ...
proposed a new line, known as the Foch Line, on July 18, 1919. The Foch Line was negotiated with the Polish war mission, led by General
Tadeusz Jordan-Rozwadowski Count Tadeusz Jordan-Rozwadowski (19 May 1866 – 18 October 1928) was a Polish military commander, diplomat, and politician, a general of the Austro-Hungarian Army and then the Polish Army. Biography Youth Jordan-Rozwadowski was born i ...
in Paris, while Lithuanian representatives were not invited. The Foch Line had two major modifications compared to the June 18 line: first, the entire line was moved west to give extra protection to the strategic
Warsaw – Saint Petersburg Railway Warsaw ( pl, Warszawa, ), officially the Capital City of Warsaw,, abbreviation: ''m.st. Warszawa'' is the capital and largest city of Poland. The metropolis stands on the River Vistula in east-central Poland, and its population is official ...
and second, the
Suwałki Region Suwałki Region ( pl, Suwalszczyzna ; lt, Suvalkų kraštas, Suvalkija, russian: cувалкщина, german: Sudauen) is a small region around the city of Suwałki (known in Lithuanian as ''Suvalkai'') in northeastern Poland near the border wit ...
, including the towns of Sejny,
Suwałki Suwałki ( lt, Suvalkai; yi, סואוואַלק) is a city in northeastern Poland with a population of 69,206 (2021). It is the capital of Suwałki County and one of the most important centers of commerce in the Podlaskie Voivodeship. Suwałki ...
,
Puńsk Puńsk ( lt, Punskas) is a village in the Podlaskie Voivodeship in northeastern Poland, seat of the Gmina Puńsk in the Sejny County. It is located only from the border with Lithuania. History Early history The oldest traces of humans in ...
, was assigned to Poland. Despite assurances at the time that the line was just a temporary measure to normalize the situation before full negotiations could take place, the southern Foch Line is the present-day
Lithuania–Poland border The Lithuania–Poland border is the state border between the Republic of Lithuania and the Republic of Poland. The length of the border is .. Page gives Polish PWN Encyklopedia as reference. It runs from the Lithuania–Poland–Russia tripo ...
. On July 26, the Foch Line was accepted by the
Conference of Ambassadors The Conference of Ambassadors of the Principal Allied and Associated Powers was an inter-allied organization of the Entente in the period following the end of World War I. Formed in Paris in January 1920 it became a successor of the Supreme War C ...
as the provisional border between the two states. Lithuanians were not informed about this decision until August 3. Neither country was satisfied: both Lithuanian and Polish forces would have to retreat from the Suwałki and Vilnius regions, respectively. Those Germans still present in the region also objected to the boundary of the line. The Lithuanian forces (about 350 strong) left the town of Suwałki by August 7, but stopped in Sejny and formed a line at the
Czarna Hańcza The Czarna Hańcza, Chornaya Hancha (, ) is the largest river of the Suwałki Region of north-eastern Poland and the Sapockin region of north-western Belarus. It is known for having large postglacial boulders. Originating near Lake Hańcza (the ...
river –
Wigry Lake Wigry ( lt, Vygriai, Vingriai) is a lake located in north-eastern part of Poland, in Podlaskie Voivodeship. Wigry lake is situated in the forests of the Augustów Wilderness – trees grow on about 80% of its shoreline. There are 19 smaller ...
, thus effectively violating the demarcation line. Lithuanians believed that the Foch Line was not the final decision, and that they had the duty to protect Lithuanian outposts in the region.


Uprising preparations

On August 12, 1919, two days after the Germans retreated from Sejny, a Polish meeting in the town attracted over 100 delegates from neighboring Polish communities; the meeting passed a resolution that "only securing the area by Polish Army can solve the problem." The Sejny branch of the
Polish Military Organization The Polish Military Organisation, PMO ( pl, Polska Organizacja Wojskowa, POW) was a secret military organization which formed during World War I (1914-1918). Józef Piłsudski founded the group in August 1914; it adopted the name ''POW'' in Novem ...
(PMO), led by Polish regular army officers Adam Rudnicki and Wacław Zawadzki, began preparing for the uprising on August 16. PMO members and local militia volunteers numbered some 900 or 1,200 men (sources vary). The uprising was scheduled for the night of August 22 to 23, 1919. The date was chosen to coincide with the withdrawal of German troops from the town of Suwałki. The Poles hoped to capture the territory up to the Foch Line and advance further to take control of the towns of
Seirijai Seirijai is a small town in Alytus County in southern Lithuania. In 2011 it had a population of 788. Etymology Seirijai toponym came from the lake ''Seirijis'', which got its name from the creek ''Seira'' name of which is of Dainavian dielect o ...
,
Lazdijai Lazdijai () is a small town in Lithuania located about east of the border with Poland. History It was established by Sigismund II Augustus Sigismund II Augustus ( pl, Zygmunt II August, lt, Žygimantas Augustas; 1 August 1520 – 7 July 15 ...
,
Kapčiamiestis Kapčiamiestis is a town in Lithuania located near the confluence of Baltoji Ančia and Nieda Rivers. History Kapčiamiestis traces its history dating back in the early 16th century, then a manor was built. In 1777 a parish-school was opened ...
as far as
Simnas Simnas is small town on the river Dovinė between Simnas and Giluitis lakes, in Alytus district, Alytus county, in the south of Lithuania. It lies on the 131 a national primary road from Alytus to Kalvarija. Simnas located within the ethnogr ...
. According to the Polish historian
Tadeusz Mańczuk ''Tadeusz'' is a Polish first name, derived from Thaddaeus. Tadeusz may refer to: * Tadeusz Bór-Komorowski (1895–1966), Polish military leader * Tadeusz Borowski (1922–1951), Polish writer and The Holocaust survivor * Tadeusz Boy-Żeleńsk ...
, Piłsudski – who was planning a coup d'état in
Kaunas Kaunas (; ; also see other names) is the second-largest city in Lithuania after Vilnius and an important centre of Lithuanian economic, academic, and cultural life. Kaunas was the largest city and the centre of a county in the Duchy of Tra ...
– discouraged the local PMO activists from carrying out the Sejny Uprising. Piłsudski reasoned that any hostilities could leave Lithuanians even more opposed to the proposed union with Poland (see
Międzymorze Intermarium ( pl, Międzymorze, ) was a post-World War I geopolitical plan conceived by Józef Piłsudski to unite former Polish–Lithuanian Commonwealth lands within a single polity. The plan went through several iterations, some of which antic ...
). The local PMO disregarded his recommendations and launched the uprising. While locally successful, it led to the failure of the nationwide coup. On August 17, a Lithuanian counter-demonstration was staged. Its participants read aloud a recently issued recruiting proclamation of the Lithuanian volunteer army: "Citizens! Our nation is in danger! To arms! We shall leave not a single occupant on our lands!" On August 20,
Prime Minister of Lithuania The prime minister of Lithuania ( lt, Ministras Pirmininkas; "Minister-Chairman") is the head of the government of Lithuania. The prime minister is Lithuania's head of government and is appointed by the president with the assent of the Lithuan ...
Mykolas Sleževičius Mykolas Sleževičius (21 February 1882 – 11 November 1939) was a Lithuanian lawyer, political and cultural figure, and journalist. One of the most influential figures in inter-war Lithuania, he served as the prime minister of Lithuania on thr ...
visited Sejny and called on Lithuanians to defend their lands "to the end, however they can, with axes, pitchforks and scythes". According to Lesčius, at the time the Lithuanian command in Sejny had only 260 infantry and 70 cavalry personnel, stretched along the long line of defense. There were only 10 Lithuanian guards and 20 clerical staff in the town itself. Mańczuk and Buchowski note that the Polish insurgents estimated the Lithuanian forces at 1,200 infantry (Mańczuk also adds an estimate of 120 cavalry), including a 400-strong garrison in Sejny.


Military skirmishes

According to the Lithuanian historian Lesčius, the first Polish assault of about 300 PMO members on August 22 was repelled, but the next day Lithuanians were forced to retreat towards
Lazdijai Lazdijai () is a small town in Lithuania located about east of the border with Poland. History It was established by Sigismund II Augustus Sigismund II Augustus ( pl, Zygmunt II August, lt, Žygimantas Augustas; 1 August 1520 – 7 July 15 ...
. Over 100 Lithuanians were imprisoned in Sejny when their commander Bardauskas sided with the Poles. The Polish insurgents also attacked Lazdijai and Kapčiamiestis, towns on the Lithuanian side of the Foch Line. In early morning of August 25, Lithuanians counterattacked and recaptured Sejny. Polish sources claim that Lithuanians there were aided by a company of Germans volunteers, but Lithuanian sources assert that it was an excuse used by Rudnicki to explain his defeat. The Lithuanian forces recovered some important documents and property, freed Lithuanian prisoners and, according to Mańczuk, executed several of the PMO fighters they found wounded. On the evening of August 25, the first regular unit (41st Infantry Regiment) of the Polish Army received an order to advance towards Sejny. The Lithuanian forces retreated on the same day when they learned about the approaching Polish reinforcements. According to Mańczuk, they based their retreat on an erroneous report about a "large Polish cavalry unit" operating to their rear; only small groups of Polish partisans operated there. Later the next day, during the afternoon of August 26, the PMO forces in Sejny were joined by the 41st Infantry Regiment. On August 26, a large anti-Polish protest took place in
Lazdijai Lazdijai () is a small town in Lithuania located about east of the border with Poland. History It was established by Sigismund II Augustus Sigismund II Augustus ( pl, Zygmunt II August, lt, Žygimantas Augustas; 1 August 1520 – 7 July 15 ...
, with cries to march on Sejny. The last Lithuanian attempt to retake the town was made on August 28. The Lithuanians (about 650 men) were defeated by the combined forces of the Polish Army (800 men) and PMO volunteers (500 men). On August 27, the Poles officially demanded that Lithuanians retreat behind the Foch Line. On September 1, Rudnicki announced incorporation of PMO volunteers into the 41st Infantry Regiment. During the negotiations on September 5, representatives of the two groups agreed to settle on a detailed demarcation line; Lithuanians agreed to retreat by September 7. The Polish regular army units did not cross the Foch Line, and refused to aid the PMO insurgents still operating on the Lithuanian side. Polish sources give total Polish casualties for the Sejny Uprising as 37 killed in action and 70 wounded.


Aftermath

After the uprising, Poland repressed Lithuanian cultural life in Sejny. Lithuanian schools in Sejny (which had some 300 pupils) and surrounding villages were closed. The local Lithuanian clergy were evicted, and the
Sejny Priest Seminary The Sejny Priest Seminary or Sejny Theological Seminary (Lithuanian: ''Seinų kunigų seminarija'') was a Catholic priest seminary established in Sejny (now Poland) in 1826. The courses lasted five years. Up until its dissolution in 1926, the semi ...
relocated. According to the Lithuanians, the repressions were even more far-reaching, including a ban on public use of the
Lithuanian language Lithuanian ( ) is an Eastern Baltic language belonging to the Baltic branch of the Indo-European language family. It is the official language of Lithuania and one of the official languages of the European Union. There are about 2.8 milli ...
and the closing of Lithuanian organizations, which had a total of 1,300 members. ''
The New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid ...
'', reporting on renewed hostilities a year later, described the 1919 Sejny events as a violent occupation by the Poles, in which the Lithuanian inhabitants, teachers, and religious ministers were maltreated and expelled. Polish historian Łossowski notes that both sides mistreated the civilian population and exaggerated reports to gain internal and foreign support. The uprising contributed to the deterioration of the
Polish–Lithuanian relations Polish–Lithuanian can refer to: * Polish–Lithuanian union (1385–1569) * Polish–Lithuanian Commonwealth (1569–1795) * Polish-Lithuanian identity as used to describe groups, families, or individuals with histories in the Polish–Lithuanian ...
and further discouraged the Lithuanians from joining the proposed
Międzymorze Intermarium ( pl, Międzymorze, ) was a post-World War I geopolitical plan conceived by Józef Piłsudski to unite former Polish–Lithuanian Commonwealth lands within a single polity. The plan went through several iterations, some of which antic ...
federation. The Sejny Uprising doomed the Polish plan to overthrow the Lithuanian government in a coup d'état. After the uprising, the Lithuanian police and intelligence intensified their investigation of Polish sympathizers and soon uncovered the planned coup. They made mass arrests of Polish activists from August 27 to the end of September 1919. During the investigations, lists of PMO supporters were found; law enforcement completely suppressed the organisation in Lithuania. Hostilities over the Suwałki Region resumed in summer 1920. When the Polish Army began to retreat during the course of 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 Lithuanians moved to secure what they claimed to be their new borders, set by the
Soviet–Lithuanian Peace Treaty The Soviet–Lithuanian Peace Treaty, also known as the Moscow Peace Treaty, was signed between Lithuania and Soviet Russia on July 12, 1920. In exchange for Lithuania's neutrality and permission to move its troops in the territory that was rec ...
of July 1920. The Peace Treaty granted Sejny and surrounding area to Lithuania. Poland did not recognize this bilateral treaty. Ensuing tensions heightened until the outbreak of the
Polish–Lithuanian War The Polish–Lithuanian War (in Polish historiography, Polish–Lithuanian Conflict) was an undeclared war between newly-independent Lithuania and Poland following World War I, which happened mainly, but not only, in the Vilnius and Suwałki reg ...
. Sejny changed hands frequently until it was controlled by Polish forces on September 22, 1920. The situation was legalized by the
Suwałki Agreement The Suwałki Agreement, Treaty of Suvalkai, or Suwalki Treaty ( pl, Umowa suwalska, lt, Suvalkų sutartis) was an agreement signed in the town of Suwałki between Poland and Lithuania on October 7, 1920. It was registered in the '' League of ...
of October 7, 1920, which effectively returned the town to the Polish side of the border.


Notes


References

* * * {{Polish wars and conflicts Conflicts in 1919 Lithuania–Poland relations Rebellions in Poland 1919 in Lithuania 1919 in Poland 20th-century rebellions Revolutions of 1917–1923