Suwałki Agreement The Suwałki Agreement , Treaty of Suvalkai , or Suwalki Treaty ( , ) was an agreement signed in the town of Suwałki between Poland and Lithuania on October 7 , 1920 . It was registered in the " League of Nations Treaty Series " on January 19 , 1922 . Both countries had re - established their independence in the aftermath of World War I and did not have well - defined borders . They waged the Polish – Lithuanian War over territorial disputes in the Suwałki and Vilnius Region s . At the end of September 1920 , Polish forces defeated the Soviets at the Battle of the Niemen River , thus militarily securing the Suwałki Region and opening the possibility of an assault on the city of Vilnius ( Wilno ) . Polish Chief of State , Józef Piłsudski , had planned to take over the city since mid - September in a false flag operation known as Żeligowski ' s Mutiny . Under pressure from the League of Nations , Poland agreed to negotiate , hoping to buy time and divert attention from the upcoming Żeligowski ' s Mutiny . The Lithuanians sought to achieve as much protection for Vilnius as possible . The agreement resulted in a ceasefire and established a demarcation line running through the disputed Suwałki Region up to the Bastuny railway station . The line was incomplete and did not provide adequate protection to Vilnius . Although neither Vilnius or the surrounding region was explicitly addressed in the agreement , numerous historians have described the agreement as allotting Vilnius to Lithuania . Shortly after the agreement was signed , the clauses calling for territorial negotiation and an end to military actions were broken by Poland . Polish general Lucjan Żeligowski , acting under secret orders from Piłsudski , pretended to disobey stand - down orders from the Polish military command and marched on Vilnius . The city was taken on October 9 . The Suwałki Agreement was to take effect at noon on October 10 . Żeligowski established the Republic of Central Lithuania which , despite intense protests by Lithuania , was incorporated into the Second Polish Republic in 1923 . The Vilnius Region remained under Polish administration until 1939 . Background . In the aftermath of World War I both Poland and Lithuania gained independence , but borders in the region were not established . The most contentious issue was Vilnius ( Wilno ) , historical capital of the Grand Duchy of Lithuania with a population , according to the 1916 German census , divided about evenly between Jews and Poles , but with only a 2 – 3 % Lithuanian minority . The Soviet – Lithuanian Peace Treaty , signed in July 1920 between Lithuania and the Russian SFSR , drew the eastern border of Lithuania . Russia recognized large territories , including the Vilnius and Suwałki Regions , as belonging to Lithuania . That month , during the Polish – Soviet War , the Red Army pushed Polish forces from the contested territories , including Vilnius . In the meantime , Lithuanians secured some other areas abandonened by the Polish army , such as the town of Suwałki . On August 6 , Lithuania and Soviet Russia signed a convention regarding withdrawal of Russian troops from the recognized Lithuanian territory . However there were indications that the Soviets planned a coup against the Lithuanian government in hopes of re - establishing the Lithuanian SSR . The Soviet troops began to retreat only after the Red Army suffered a heavy defeat in Poland at the Battle of Warsaw in mid - August . The Polish Army pushed back and came in contact with the Lithuanians in the contested Suwałki Region . The diplomatic negotiations broke down . The Lithuanians claimed to be defending their borders , while Poland did not recognize the Soviet – Lithuanian Peace Treaty and claimed that the Lithuanians had no rights to these territories . Poland also accused the Lithuanians of collaborating with the Soviets and thus violating the declared neutrality in the Polish – Soviet War . In the ensuing hostilities , the towns of Suwałki , Sejny , and Augustów changed hands frequently . The diplomatic struggle , both directly between the two states and in the League of Nations , intensified . Negotiations . Pressure from the League of Nations . On September 5 , 1920 , Polish Foreign Minister Eustachy Sapieha delivered a diplomatic note to the League of Nations asking it to intervene in the Polish – Lithuanian War . He claimed that Lithuania allowed free passage through its territory for Soviet troops and therefore violated its declared neutrality in the Polish – Soviet War . The next day Lithuania responded with a direct note to Poland in which Lithuanian Foreign Minister Juozas Purickis proposed to negotiate a demarcation line and other issues in Marijampolė . On September 8 , during a planning meeting for what later was the Battle of the Niemen River , the Poles decided to maneuver through the Lithuanian territory to the rear of the Soviet Army . In an attempt to conceal the planned attack , Polish diplomats accepted the proposal to negotiate . The negotiations started on September 16 in Kalvarija , but collapsed just two days later . The League of Nations began its session on September 16 , 1920 . After reports by Lithuanian representative Augustinas Voldemaras and Polish envoy Ignacy Jan Paderewski , the League adopted a resolution on September 20 . It urged both states to cease hostilities and adhere to the Curzon Line . Poland was asked to respect Lithuanian neutrality if Soviet Russia agreed to do the same . A special Control Commission was to be dispatched into the conflict zone to oversee implementation of the resolution . The Lithuanian government accepted the resolution . Sapieha replied that Poland could not honor the Lithuanian neutrality or the demarcation line as Lithuania was actively collaborating with the Soviets . The Poles reserved the right of full freedom of action . The Lithuanian representative in London , Count Alfredas Tiškevičius , informed the secretariat of the League of Nations that Sapieha ' s telegram should be regarded as a declaration of war ; he also asked that the League of Nations take immediate intervention in order to stop new Polish aggressive acts . On September 22 , 1920 , Poland attacked Lithuanian units in the Suwałki Region as part of the Battle of the Niemen River . The Polish army took prisoner 1 , 700 Lithuanian troops who had surrendered . Polish forces then marched , as planned during the September 8 meeting , across the Neman River near Druskininkai and Merkinė to the rear of the Soviet forces near Hrodna and Lida . The Red Army retreated . This attack , just two days after the League ' s resolution , damaged both Poland ' s and the League ' s reputation . Some politicians began to view Poland as an aggressor while the newly formed League realized its own shortcomings in light of such defiance . On September 26 , urged by the League , Sapieha proposed new negotiations in Suwałki . Lithuania accepted the proposal on the following day . Negotiations in Suwałki . At the time of the negotiations , the military situation on the ground was threatening Lithuania not only in the Suwałki Region , but also in Vilnius . The Polish leader , Józef Piłsudski , feared that the Entente and the League might accept the " fait accompli " that had been created by the Soviet transfer of Vilnius to Lithuania on August 26 , 1920 . Already on September 22 , Sapieha asked Paderewski to gauge the possible reaction of the League in case military units in the Kresy decided to attack Vilnius , following the example of the Italian Gabriele D ' Annunzio , who in 1919 staged a mutiny and took over the city of Fiume . By agreeing to the negotiations , the Poles sought to buy time and distract attention from the Vilnius Region . The Lithuanians hoped to avoid new Polish attacks and , with help of the League , to settle the disputes . The conference began in the evening of September 29 , 1920 . The Polish delegation was led by colonel Mieczysław Mackiewicz ( who originated from Lithuania ) , and the Lithuanian delegation by general Maksimas Katche . Lithuania proposed an immediate armistice , but the Polish delegation refused . Only after the Lithuanian delegation threatened to leave the negotiation table did Poland agree to stop fighting , but only to the east of the Neman River ( the Suwałki Region ) . Fighting to the west of the river continued . The Polish delegates demanded that the Lithuanians allow the Polish forces to use a portion of the Warsaw – Saint Petersburg Railway and the train station in Varėna ( Orany ) . The Lithuanians refused : their major forces were concentrated in the Suwałki Region and moving them to protect Vilnius without the railway would be extremely difficult . The Lithuanian side was ready to give up the Suwałki Region in exchange for Poland ' s recognition of the Lithuanian claims to Vilnius . The Lithuanian delegation , after consultations in Kaunas on October 2 , proposed their demarcation line on October 3 . The line would be withdrawn about from the border determined by the Soviet – Lithuanian Peace Treaty . On October 4 , the Polish delegation , after consultations with Piłsudski , presented a counter - offer . In essence , the Lithuanians wanted a longer demarcation line to provide better protection for Vilnius and the Poles pushed for a shorter line . While Vilnius was not a topic of debate , it was on everybody ' s mind . On the same day the Control Commission , sent by the League according to its resolution of September 20 , arrived in Suwałki to mediate the talks . The commission , led by French colonel Pierre Chardigny , included representatives from Italy , Great Britain , Spain , and Japan . On October 5 , 1920 , the Control Commission presented a concrete proposal to draw the demarcation line up to the village of Utieka on the Neman River , about south of Merkinė ( Merecz ) , and to establish a wide neutral zone along the line . On October 6 , negotiations continued regarding an extension of the demarcation line . The Poles refused to move it past the village of Bastuny , claiming that the Polish army needed freedom to maneuver against the Soviet troops , even though a provisional ceasefire agreement had been reached with Soviet Russia on October 5 . The Poles proposed to discuss further demarcation lines in Riga , where Poland and Russia negotiated the Peace of Riga . On the same day fighting west of the Neman River ceased as Polish troops captured the Varėna train station . On October 7 , at midnight , the final Suwałki Agreement was signed . On October 8 , the Control Commission stated that they could not see why the demarcation line could not be extended further than Bastuny and urged another round of negotiations . Provisions of the agreement . The agreement was finally signed on October 7 , 1920 ; the ceasefire was to begin at noon on October 10 . Notably , the treaty made not a single reference to Vilnius or the Vilnius Region . The agreement contained the following articles : Aftermath . The demarcation line drawn through the Suwałki Region for the most part remains the border between Poland and Lithuania in modern times ; notably the towns of Sejny , Suwałki and Augustów remained on the Polish side . In the 21st century , the Suwałki Region ( the present - day Podlaskie Voivodeship ) remains home to the Lithuanian minority in Poland . The most controversial issue – the future of the city of Vilnius – was not explicitly addressed . When the agreement was signed , Vilnius was garrisoned by Lithuanian troops and behind the Lithuanian lines . Yet this changed almost immediately when the staged Żeligowski ' s Mutiny began on October 8 . Soon after the mutiny , Léon Bourgeois , President of the Council of the League of Nations , expressed strong disapproval , asserting that Żeligowski ' s actions were a violation of the engagements entered into with the Council of the League of Nations , and demanding the immediate Polish evacuation of the city . In Piłsudski ' s view , signing even such a limited agreement was not in Poland ' s best interests , and he disapproved of it . In a 1923 speech acknowledging that he had directed Żeligowski ' s coup , Piłsudski stated : " I tore up the Suwałki Treaty , and afterwards I issued a false " communique " by the General Staff . " Żeligowski and his mutineers captured Vilnius , established the Republic of Central Lithuania , and after a disputed election in 1922 , incorporated the republic into Poland . The conflict over the city dragged on until World War II . In the 21st century , the Vilnius Region ( " Wileńszczyzna " ) is the major center of the Polish minority in Lithuania . Evaluations and historiography . While the Lithuanian side considered the agreement to be an enforceable political treaty , the Polish side considered it to be a minor military agreement , later superseded by a ceasefire agreement between Lithuania and Żeligowski reached on November 29 . American historian Alfred Erich Senn has argued that it was not a regular political treaty , as it did not require ratification , but the presence of political representatives of both sides indicated that it was not a mere military agreement . Poland and Lithuania also disagreed about the agreement ' s relation to the Vilnius question , which was not explicitly addressed in the treaty . The Lithuanian side considered that the agreement assigned Vilnius to Lithuania , while the Polish side argued that it did not concern Vilnius or other territorial claims . Senn has described the agreement as tacitly leaving Vilnius to Lithuania . Finally , the Lithuanian side considered the Żeligowski ' s attack on Vilnius a violation of the Suwałki agreement and as a major argument in international mediation . Poland disagreed and protested such interpretation of the document . At first Poland claimed that Żeligowski was a rebel who acted without approval from the Polish government . Later Piłsudski ' s role in the attack was acknowledged , but the Polish side argued that the agreement was not violated , as the attack was held to the east from the demarcation line . The League of Nations considered the Polish attack a violation of the agreement , but placed emphasis on resumption of the hostilities and not subsequent territorial changes . Senn said the view that the agreement has not been violated was " specious " . In his opinion , Piłsudski himself did not seem to share that view , as evidenced by his attempt to pretend that the attacking forces were " rebels " . In most cases historians tend to summarise the issue by saying that the agreement assigned Vilnius to Lithuania and Polish attack violated it . However , Piotr Łossowski argued that such summaries are inadequate and misleading .