The Polish–Lithuanian War was an armed conflict between newly independent Lithuania and Poland in the aftermath of World War I. The conflict primarily concerned territorial control of the Vilnius Region, including Vilnius, and the Suwałki Region, including the towns of Suwałki, Augustów, and Sejny. The conflict was largely shaped by the progress in the Polish–Soviet War and international efforts to mediate at the Conference of Ambassadors and later the League of Nations. There are major differences in Polish and Lithuanian historiography regarding treatment of the war. According to Lithuanian historians, the war was part of the Lithuanian Wars of Independence and spanned from spring 1919 to November 1920. According to Poland, the war included only fighting over the Suwałki Region in September–October 1920 and was part of the Polish–Soviet War.
In April 1919, Poland captured Vilnius and came in contact with the Lithuanian Army fighting in the Lithuanian–Soviet War. Faced with a common enemy, the Polish–Lithuanian relations were not immediately hostile. Poland hoped to persuade Lithuania to join some kind of Polish–Lithuanian union (see the Międzymorze federation), which Lithuania saw as loss of independence to Polish federalism. As bilateral relations worsened, the Entente drew two demarcation lines in hopes to stall further open hostilities. The lines did not please anyone and were ignored. When a Polish coup against the Lithuanian government failed in August 1919, the front stabilized until summer 1920.
In July 1920, Poland was losing the Polish–Soviet War and was in full retreat. The Lithuanians followed retreating Polish troops to secure the territory, assigned to Lithuania by the Soviet–Lithuanian Peace Treaty. The Soviets were the first to enter Vilnius. When Poland achieved a major victory in the Battle of Warsaw and forced the Soviets to retreat in August 1920, Lithuanians defended their new borders. Poland did not recognize the Peace Treaty and claimed that Lithuania had become a Soviet ally. Fighting broke out in the Suwałki Region. During the Battle of the Niemen River, Poland attacked Lithuania on a wide front. The battle drastically altered the military situation and left Vilnius open to an attack. Under pressure from the League of Nations, Poland signed the Suwałki Agreement on October 7, 1920. The agreement drew a new demarcation line, which was incomplete and did not provide protection to Vilnius.
On October 8, 1920, Polish general Lucjan Żeligowski staged a mutiny among Polish troops and marched on Vilnius to "defend the right of self-determination of local Poles." The mutiny was planned and authorized by Polish chief of state Józef Piłsudski. Żeligowski's forces captured Vilnius, but further advances were stopped by the Lithuanian troops. Żeligowski proclaimed creation of the Republic of Central Lithuania with capital in Vilnius. On November 29, a ceasefire was signed. The prolonged mediation by the League of Nations did not change the situation and status quo was accepted in 1923. The Republic of Central Lithuania was incorporated into Poland as the Wilno Voivodeship in 1922. Lithuania did not recognize these developments and continued to claim Vilnius as its constitutional capital. There were no diplomatic relations between Poland and Lithuania until the Polish ultimatum of 1938.
World War I ended on November 11, 1918 when Germany signed the Compiègne Armistice. On November 13, Soviet Russia renounced the Treaty of Brest-Litovsk and began the Soviet westward offensive of 1918–1919. The Bolsheviks followed retreating German troops and attacked Lithuania and Poland from the east trying to prevent their independence. They attempted to spread the global proletarian revolution, establish Soviet republics in the region, and join the German and the Hungarian Revolutions. The Soviet offensive sparked a series of local wars, including the Polish–Soviet War and the Lithuanian–Soviet War. At first, the Soviets were successful, but came to a halt in February 1919. In March–April both Lithuanians and Poles began their offensives against the Soviets. The three armies met in the Vilnius Region. Polish–Lithuanian relations at the time were not immediately hostile, but grew worse as each side refused to compromise. On April 19, 1919, the Polish Army captured Vilnius.
At first, both Poles and Lithuanians cooperated against the Soviets, but soon the cooperation gave way to increasing hostility. Lithuania claimed neutrality in the Polish–Soviet War. As the Polish Army forced its way further into Lithuania, the first clashes between Polish and Lithuanian soldiers occurred on April 26 and May 8, 1919, near Vievis. Though there was no formal state of war and few casualties, by July newspapers reported increasing clashes between Poles and Lithuanians, primarily around the towns of Merkinė and Širvintos. Direct negotiations in Kaunas between May 28 and June 11, 1919, collapsed as neither side agreed to compromise. Lithuania tried to avoid direct military conflict and submitted its case for mediation to the Conference of Ambassadors.
Due to Polish-Lithuanian tensions, the allied powers withheld diplomatic recognition of Lithuania until 1922. Poland did not recognize independence of Lithuania as Polish leader Józef Piłsudski hoped to revive the old Polish–Lithuanian Commonwealth (see the Międzymorze federation) and campaigned for some kind of Polish–Lithuanian union in the Paris Peace Conference. Poland also did not intend to make any territorial concessions, justifying its actions not only as part of a military campaign against the Soviets but also as the right of self-determination of local Poles. According to the 1897 Russian census, the disputed city of Vilnius had an ethnic breakdown of 30% Poles, 40% Jews, and 2% Lithuanians; however the percentage of Lithuanians was higher in the surrounding countryside. According to the 1916 German census, Poles were the most numerous among all local nationalities and constituted 53% or 53,67% of the city's population, 50% in the entire Vilnius census region and the vast majority in the Vilnius census district. The Lithuanians claimed Vilnius as their historical capital and refused any federation with Poland, desiring an independent Lithuanian state. They regarded Polish federalism as recreation of Polish cultural and political dominance. The Lithuanian government in Kaunas, designated as the temporary capital, saw the Polish presence in Vilnius as occupation. In addition to the Vilnius Region, the Suwałki Region was also disputed. It had mixed Polish and Lithuanian population.
At the time international situations of newly independent Poland and Lithuania were unequal. Poland, much larger in territory and population, was dedicated point #13 in Woodrow Wilson's Fourteen Points. It was recognized by all nations of the Entente, officially invited to the Paris Peace Conference, and became one of the founding members of the League of Nations. Poland also enjoyed a close alliance with France. Lithuania did not receive international recognition (it was first recognized de jure in July 1920 by Soviet Russia) as the Entente hoped to revive the Russian Empire within its former territory, which included Lithuania. Not invited to any post-war diplomatic conferences, it also had to battle negative propaganda that the Council of Lithuania was a German puppet, that Lithuanians harbored pro-Bolshevik attitudes, or that Lithuania was too small and weak to survive without a union with Poland.
The Conference of Ambassadors drew the first demarcation line on June 18. The line, drawn about 5 km (3.1 mi) west of the Warsaw – Saint Petersburg Railway, was based on the military situation on the ground rather than ethnic composition. Neither Poles nor Lithuanians were content with the line. The Polish Ministry of Foreign Affairs rejected the line as it would require the Polish forces to retreat up to 35 km (22 mi). The Lithuanians protested leaving Vilnius and Hrodna under Polish control. As German volunteers were departing from Lithuania and Lithuanian forces were preoccupied with battles against the Soviets in northern Lithuania, Poland mounted an offensive on 100 km (62 mi) wide front moving 20–30 km (12–19 mi) deeper into the Lithuanian territory.
On July 18, Ferdinand Foch proposed the second demarcation line, known as the Foch Line. It was approved by the Entente on July 26. The Lithuanians were informed about the new line only on August 3. Two major modifications favorable to the Poles were made: the Suwałki Region was assigned to Poland and the entire line was moved about 7 km (4.3 mi) west. Again, both Poles and Lithuanians protested the line as it would require them to withdraw their armies from the Vilnius and Suwałki Regions respectively. German administration, which had not yet retreated from the Suwałki Region, also opposed the Foch Line. The new line did not immediately halt the hostilities. After a couple of Polish attacks on July 29 and August 2, the front stabilized.
The Lithuanians obeyed the Foch Line and retreated from Suwałki on August 7, 1919. However, they stopped in ethnically mixed Sejny and formed a line on the Czarna Hańcza river – Wigry Lake. They showed their intention to stay there permanently, which caused concern among the local Poles. On August 12, they organized a rally of about 100 people demanding incorporation into Poland. The Sejny branch of Polish Military Organization (PMO) began preparing for an uprising, scheduled for the night of August 22 to 23, 1919. Between 900 and 1,200 partisans joined PMO forces. On August 23, the Poles captured Sejny and attacked Lazdijai and Kapčiamiestis, towns on the Lithuanian side of the Foch Line. The insurgents planned to march as far as Simnas. Lithuanians recaptured Sejny on August 25 for a few hours. On August 26, Polish regular forces – the 41st Infantry Regiment – joined the PMO volunteers. On September 5, the Lithuanians agreed to withdraw behind the Foch Line by September 7. Poland secured Sejny and repressed Lithuanian cultural life: the Sejny Priest Seminary was expelled, Lithuanian schools and cultural organizations closed. After the uprising, the mistrust of Poles prompted Lithuanian intelligence to intensify its investigations of Polish activities in Lithuania. This helped to detect and prevent a planned coup d'état in Kaunas to overthrow the government of Lithuania.
Sometime in mid-July 1919, PMO forces in Vilnius began planning a coup to replace the Lithuanian government with a pro-Polish cabinet, which would agree to a union with Poland (the proposed Międzymorze federation). Polish leader Józef Piłsudski believed there were enough Polish sympathizers in Lithuania to carry out the coup. On August 3, a Polish diplomatic mission, led by Leon Wasilewski, in Kaunas had a double purpose: propose a plebiscite in the contested territories and assess preparedness for the coup. On August 6, the Lithuanian government rejected the plebiscite proposal, stating that the disputed territories constitute ethnographic Lithuania. PMO planned to capture and hold Kaunas for a few hours until arrival of the regular Polish troops, situated only some 40–50 km (25–31 mi) east from the city. The coup would be portrayed as an initiative of local population to "free Lithuania from German influence" while denouncing any involvement of the Polish government. Polish newspapers ran a propaganda campaign claiming that the Council of Lithuania was simply a German puppet. The coup was initially scheduled for the night of August 27 to 28, but was postponed to September 1. Lithuanian intelligence discovered the coup, but did not have a list of PMO members. Lithuanian authorities began mass arrests of some 200 Polish activists, including some officers of the Lithuanian Army. Kaunas was declared under the state of siege. Polish press saw mass arrests of Polish activists "to whom no charge can be ascribed other than being Poles" as proof of systematic anti-Polish policies of the German-ridden Lithuanian government. PMO was little affected by the arrests and scheduled another coup attempt for the end of September. However, Lithuanians obtained a full PMO membership list and liquidated the organization in Lithuania.
After the failure of the coup in Kaunas, there were numerous small border incidents. On September 19, 1919, Polish troops attacked Gelvonai and encroached towards Ukmergė. On several occasions fights broke out regarding strategically important bridge over the Šventoji River near Vepriai. In October, when main Lithuanian forces were deployed against the Bermontians in northwestern Lithuania, the attacks intensified. Poles captured Salakas on October 5 and attacked Kapčiamiestis on October 12. The front stabilized, but harassment of border guards and local villagers continued throughout late 1919 and early 1920. In March 1920, the Poles attacked along the railroad stations in Kalkūni and Turmantas. The situation was investigated by British and French observers and reported to the Entente. The situation somewhat improved only in late spring 1920 when most Polish troops were deployed in Ukraine during the Polish–Soviet War.
At the time Lithuania faced a severe budget crisis – in 1919 its revenue was 72 million while expenses reached 190 million German marks. While the government was struggling to obtain financial assistance and loans, deep cuts affected the army. Instead of increasing its armed forces to 40,000 men, Lithuania was forced to cut them to about 25,000.
In April 1920 Poland launched the large-scale Kiev Offensive in hopes to capture Ukraine. Initially successful, the Polish Army started retreating after Russian counterattacks in early June 1920. Soon the Soviet forces began to threaten Poland's independence as they reached and crossed the Polish borders. On July 9, Polish Prime Minister Władysław Grabski asked the Allied Powers in the Spa Conference for military assistance in the war with the Soviets. The conference proposed that the Polish forces would withdraw behind the Curzon Line, the Soviet forces would stop 50 km (31 mi) to the east of the line, the Lithuanian forces would take control of Vilnius, and all other disputes would be settled via negotiations in London. Grabski opposed the transfer of Vilnius, but under pressure of British Prime Minister Lloyd George, agreed to the resolution on July 10.
At the same time Soviets and Lithuanians negotiated the Soviet–Lithuanian Peace Treaty, which was signed on July 12, 1920. Russia recognized Lithuanian independence and withdrew any territorial claims. The treaty drew the eastern border of Lithuania, which the Lithuanians continued to claim as their de jure state border until World War II. Vilnius Region, including Brasłaŭ, Hrodna, Lida, and Vilnius, was recognized to Lithuania. On August 6, after long and heated negotiations, Lithuania and Soviet Russia signed a convention regarding withdrawal of Russian troops from the recognized Lithuanian territory. However, the troops began to retreat only after the Red Army suffered a heavy defeat in Poland.
The Bolshevik forces reached the Lithuanian territory on July 7, 1920, and continued to push the Polish troops. The Lithuanian Army moved to secure territories abandoned by the retreating Polish forces. They took Turmantas on July 7, Tauragnai and Alanta on July 9, Širvintos and Musninkai on July 10, Kernavė, Molėtai, and Giedraičiai on July 11, Maišiagala and Pabradė on July 13. On July 13 the Polish command decided to transfer Vilnius to the Lithuanians in accordance with the resolution of the Spa Conference. Lithuanians moved in, but their trains were stopped by Polish soldiers near Kazimieriškės. This delay meant that the Bolsheviks were the first to enter Vilnius on July 14. By the time first Lithuanian troops entered the city on July 15, it was already secured by the Soviets. Poland sought to have Russians in the city as it would create much less complications when Polish Army counterattacked. Despite the Peace Treaty, the Soviets did not intend to transfer the city to the Lithuanians. Indeed, there were indications that the Soviets planned a coup against the Lithuanian government in hopes to re-establish the Lithuanian SSR.
Despite the setback in Vilnius, the Lithuanians continued to secure territories in the Suwałki Region. They took Druskininkai on July 17, Vištytis, Punsk, Giby, and Sejny on July 19, Suwałki on July 29, Augustów on August 8. The Polish units, afraid of being surrounded and cut off from the main Polish forces, retreated towards Łomża. The Lithuanian authorities started to organize themselves in the regained areas.
Poland claimed that Lithuania violated its claim to neutrality in the Polish–Soviet War and in effect became a Soviet ally. A secret clause of the Soviet–Lithuanian Peace Treaty allowed Soviet forces unrestricted movement within the Soviet-recognized Lithuanian territory for the duration of Soviet hostilities with Poland. This clause was of a practical matter: Soviet troops already occupied much of the assigned territory and could not withdraw while hostilities with Poland continued. Lithuanians were also simply unable to resist Soviet troops. For example, when Lithuanians refused a permission to use a road, the Soviets ignored Lithuanian protests and transported their troops and equipment regardless. At the same time Polish soldiers were disarmed and interned. The largest group, a brigade under colonel Pasławski, was interned on July 18, 1920, near Kruonis. On August 10, Lithuanians held 103 Polish officers and 3,520 private soldiers. Poland also claimed that the Lithuanian troops actively participated in military operations of the Red Army. This charge, based on memoirs of Soviet officials, lacks evidence. Further military clashes between Polish and Lithuanian troops in the Suwałki Region were interpreted by Poland to show that "the Lithuanian government has become an instrument of the Soviet government." Lithuania responded that it was defending its borders.
The Russians suffered a great defeat in the Battle of Warsaw in mid-August 1920 and started withdrawing. They handed over Vilnius to the Lithuanians on August 26. The Lithuanians hastily made preparations to secure the border, as determined by the Soviet–Lithuanian Peace Treaty. The soldiers were ordered to maintain neutrality: avoid hostilities and intern any Soviet or Polish troops that would cross the border. On August 26, a Polish delegation, led by colonel Mieczysław Mackiewicz, arrived in Kaunas to negotiate the situation. The Poles, lacking authority to discuss political issues, were concerned with military aspects. They sought permission to transport Polish troops through the territory of Lithuania, wanted access to a portion of the Warsaw – Saint Petersburg Railway, and demanded that the Lithuanian troops would withdraw from the Suwałki Region behind the Curzon Line. The Lithuanians refused to discuss military matters without a clear political Polish–Lithuanian border, that would be respected after the war. Due to these fundamental disagreements and Polish attacks, the negotiations broke down on August 30.
The Suwałki Region had strategic importance in the Polish–Soviet War. Following orders of Edward Rydz-Śmigły, Polish forces took Augustów from Lithuanians in a surprise attack on August 28. Confused and disoriented, Lithuanians retreated from Suwałki and Sejny on August 30 and 31. The Lithuanians reorganized, gathered their forces (11 battalions with 7,000 soldiers), and organized a counterattack to "defend their border" on September 2. The goal was to take and secure the Augustów–Lipsk–Hrodna line. The Lithuanians succeeded in taking Sejny and Lipsk and by September 4 reached the outskirts of Augustów. On September 5, the Poles counterattacked and forced the Lithuanians to retreat. On September 9, the Polish forces recaptured Sejny, but the Lithuanians pushed back and regained Sejny and Giby on September 13 and 14. Pending direct negotiations, hostilities were ceased on both sides.
On September 6, Lithuanian Foreign Minister Juozas Purickis proposed direct negotiations in Marijampolė. On September 8, during a planning meeting of the Battle of the Niemen River, the Poles decided to maneuver through the Lithuanian-held territory to the rear of the Soviet Army, stationed in Hrodna. 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.
On September 5, 1920, Polish Foreign Minister Eustachy Sapieha delivered a diplomatic note to the League of Nations alleging the Lithuania violated its neutrality and asking to intervene in the Polish–Lithuanian War. The League agreed to mediate and began its session on September 16. The resolution, adopted on September 20, 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. Also a special Control Commission was to be dispatched into the conflict zone to oversee implementation of the resolution. It was clear that the League had only a narrow goal to prevent armed hostilities and not to resolve the underlying territorial dispute. The Lithuanian government accepted the resolution, while Poland reserved full freedom of action in preparation for the attack on the Soviets.
On September 22, 1920, Poland attacked Lithuanian units in the Suwałki Region on a wide front. Overwhelmed by 4–5 times larger Polish forces, some 1,700–2,000 Lithuanian troops surrendered and were taken prisoner. Polish forces then marched, as planned on September 8, across the Neman River near Druskininkai and Merkinė to the rear of the Soviet forces near Hrodna and Lida. The Red Army hastily retreated. The Lithuanians had had limited intelligence warning that such an attack might occur, but chose an inadequate defensive strategy and spread their forces too thinly along the entire Polish–Lithuanian front without sufficient forces to protect the bridges across the Neman. This attack, just two days after the resolution by the League of Nations to cease hostilities, put more pressure on Poland to settle the dispute peacefully. On September 26, the Poles captured Hrodna and the Polish foreign minister proposed new negotiations in Suwałki. The Battle of the Niemen River drastically altered the balance of power: Vilnius, in Lithuanian hands since August 26, was now exposed to a Polish attack. Indeed, the Poles had already decided to capture the city and used the negotiations in Suwałki to stall and buy the time necessary to make preparations. The Lithuanian side was ready to give up the Suwałki Region in exchange for Poland's recognition of the Lithuanian claims to Vilnius.
The negotiations between Poles, led by colonel Mieczysław Mackiewicz, and Lithuanians, led by general Maksimas Katche, began in the evening of September 29, 1920. Both sides agreed to an armistice, but only to the east of the Neman River (the Suwałki Region). Fighting to the west on the river continued around Marcinkonys, Zervynos, Perloja, Eišiškės. The major point of contention, both diplomatic and military, was the train station in Varėna (Orany) on the Warsaw – Saint Petersburg Railway. Major Lithuanian forces were still concentrated in the Suwałki Region and moving them to protect Vilnius without the railway would be extremely difficult. Fighting west of the Neman River ceased only on October 6, when Polish troops had already captured the train station in Varėna.
Negotiations regarding the demarcation line were difficult. In essence, the Lithuanians wanted a longer demarcation line to provide better protection for Vilnius. The Poles agreed only to a short line in order to provide the planned attack on Vilnius with space for operation. The Polish delegation was also stalling to buy time for necessary preparations for an attack on Vilnius. While Vilnius was not a topic of debate, it was on everybody's mind. On October 4, the Control Commission, sent by the League according to its resolution of September 20, arrived to Suwałki. The Commission, led by French colonel Pierre Chardigny, re-energized the negotiations. On October 7, at midnight, the final agreement was signed. The treaty made not a single reference to Vilnius or the Vilnius Region. The ceasefire was effective only along the demarcation line, which ran through the Suwałki Region to the train station in Bastuny. Thus the line was incomplete, did not provide protection to the Vilnius Region, but indicated it would be left on the Lithuanian side.
Polish chief of state Józef Piłsudski ordered his subordinate, General Lucjan Żeligowski, to stage a mutiny with his 1st Lithuanian–Belarusian Division (16 battalions with 14,000 soldiers) in Lida and capture Vilnius in fait accompli. The rebellion had two main goals: capture Vilnius and preserve Polish international reputation. The League of Nations was mediating other Polish disputes, notably over the Free City of Danzig and Upper Silesia, and direct aggression against Lithuania could have hampered Polish bargaining positions. While the Polish side officially held Żeligowski to be a deserter and did not support him, Poland provided logistic support, including munitions and food rations, to his units. Żeligowski also received reinforcements, when, according to the official version, the mutiny spread further among the Polish troops. His initial attack was secured on both sides by two Polish Armies.
The Żeligowski's Mutiny, in planning since mid-September, began in the early morning on October 8, 1920, – just few hours after the signing of the Suwałki Agreement. A provisional agreement was made in the Polish–Soviet War, which freed up Polish units for the attack on Lithuania. As part of the ruse, Żeligowski wrote a note to Polish command announcing his mutiny and expressing his disappointment with the Suwałki Agreement. He claimed that his troops marched to defend the right of self-determination of local Polish population.
The Lithuanians were not prepared for the assault. They had only two battalions, stationed near Jašiūnai and Rūdninkai along the Merkys River, shielding the city from Poland. Their main forces were still in the Suwałki Region and to the west from Druskininkai and Varėna. Without the railway, Lithuanian units could not be easily redeployed to protect Vilnius. After it became clear that Żeligowski would not stop in Vilnius, Commander of the Lithuanian Army Silvestras Žukauskas, who had recently taken the position on October 6, ordered the city evacuated on the afternoon on October 8. They left the city's administration to Entente official Constantin Reboul. Żeligowski entered Vilnius the following evening. He did not recognize Reboul's authority and Entente officials left the city in protest. On October 12, Żeligowski proclaimed the independence of the Republic of Central Lithuania, with Vilnius as its capital. The name aligned with Piłsudski's vision of historical Lithuania, divided into three cantons: Lithuanian-inhabited Western Lithuania with its capital in Kaunas, Polish-inhabited Central Lithuania with its capital in Vilnius, and Belarusian-inhabited Eastern Lithuania with its capital in Minsk. Further developments of other cantons was prevented by Polish National Democracy, a party opposed to Piłsudski's federalist ideas.
Żeligowski's units continued to advance: territories east of the city were taken without resistance while Lithuanians defended in the west. Żeligowski took Švenčionys and Rūdiškės on October 10, Nemenčinė on October 11, Lentvaris on October 13, Rykantai on October 15. The front somewhat stabilized on the southern (left) side of the Neris River, but fighting continued on the northern (right) side of Neris. When Polish cavalry maneuvered towards Riešė, it learned from local population the location of the command of the 1st Riflemen Division. On October 21, the cavalry raided the village and took the entire command prisoner. Left without their commanders, the Lithuanians retreated and Poles took Maišiagala and Paberžė. On October 26, another cavalry raid captured Dubingiai, Giedraičiai and Želva and threatened Ukmergė. However, Lithuanians counterattacked and took back Želva on October 30 and Giedraičiai on November 1. For a while, the front stabilized.
On November 17, the mutineers began a major attack. They planned to capture Kaunas, thus threatening Lithuanian independence, by encircling the city from north through Širvintos–Ukmergė–Jonava and Giedraičiai–Kavarskas–Kėdainiai. Żeligowski's forces were about three times larger: 15 Polish battalions against 5 Lithuanian battalions. One cavalry brigade managed to break through the Lithuanian defense lines near Dubingiai, reached Kavarskas, and continued towards Kėdainiai. However, Lithuanians were successful in stopping an attack towards Ukmergė near Širvintos on November 19. About 200 Lithuanians maneuvered through swamps to the rear of three Polish battalions. Attacked from the front and rear, some 200 Poles were taken prisoner while others retreated. The Lithuanians continued to attack and captured Giedraičiai on November 21. On the same day, a ceasefire was signed under pressure from the League of Nations. The Polish cavalry brigade, pushed from Kėdainiai and cut off from its main forces, retreated through Ramygala–Troškūnai–Andrioniškis–Lėliūnai and rejoined Żeligowski's other units only on November 24.
On October 11, 1920, Lithuanian envoy in Paris Oscar Milosz asked the League of Nations to intervene in the renewed conflict with Poland. On October 14, Chairman of the League Léon Bourgeois issued a note condemning the aggression and asking Polish units to retreat. Politicians in London even considered expelling Poland from the League. When the League heard both arguments on October 26–28, Polish envoy Szymon Askenazy claimed that there was no conflict between Poland and Lithuania to mediate. He maintained that the old conflict ended with signing ceasefires with Lithuania on October 7 and with Soviet Russia on October 12 and the new conflict was caused by Żeligowski, who acted without approval from the Polish command, but with moral support of the entire Polish nation. Lithuanian envoy Augustinas Voldemaras argued that Poland orchestrated the mutiny and demanded strict sanctions against Poland. The League refused to validate Żeligowski's action. It suggested to hold a plebiscite in the contested areas. On November 6 and 7, both sides agreed and Lithuanians began preparatory work.
On November 19, Żeligowski proposed the Control Commission, led by Chardigny, to cease hostilities. Lithuanians agreed and a ceasefire was signed on November 21. Later this episode was criticized by Lithuanian commentators as at the time the Lithuanian Army had initiative in the front and had a chance of marching on Vilnius. However, the Lithuanians trusted the League of Nations would resolve the dispute in their favor and were afraid that in case of an attack on Vilnius regular Polish forces would arrive to reinforce Żeligowski's units.
Negotiations for a more permanent armistice, under mediation of the Control Commission, began on November 27 in Kaunas. Lithuania did not agree to negotiate directly with Żeligowski and thus legitimizing his actions. Therefore, Poland stepped in as a mediator. Lithuania agreed as it hoped to put the talks back into the context of the Suwałki Agreement. Poles rejected any withdrawal of Żeligowski's forces. No agreement could be reached regarding a demarcation line. On November 29, 1920, it was agreed only to cease hostilities on November 30, to entrust the Control Commission with establishment of a 6 km (3.7 mi) wide neutral zone, and to exchange prisoners. This neutral zone existed until February 1923.
In March 1921, the plans for a plebiscite were abandoned. Neither Lithuania, which was afraid of a negative result, nor Poland, which saw no reason to change status quo, wanted the plebiscite. The parties could not agree in which territory to carry out the vote and how Żeligowski's forces should be replaced by League's forces. The League of Nations then moved on from trying to solve the narrow territorial dispute in the Vilnius Region to shaping the fundamental relationship between Poland and Lithuania. During 1921, Belgian Paul Hymans suggested several Polish–Lithuanian federation models, all rejected by both sides. In January 1922, parliamentary election to the Wilno Diet (Sejm wileński) resulted in a landslide Polish victory. In its first session on February 20, 1922, the Diet voted for incorporation into Poland as the Wilno Voivodeship. Polish Sejm accepted the resolution of the Diet. The League of Nations ended its efforts to mediate the dispute. After Lithuanians seized the Klaipėda Region in January 1923, the League saw recognition of Lithuanian interest in Klaipėda as adequate compensation for the loss of Vilnius. The League accepted the status quo in February 1923 by dividing the neutral zone and setting a demarcation line, which was recognized in March 1923 as the official Polish–Lithuanian border. Lithuania did not recognize this border.
Historians have asserted that if Poland had not prevailed in the Polish–Soviet War, Lithuania would have been invaded by the Soviets, and would never have experienced two decades of independence. Despite the Soviet–Lithuanian Treaty of 1920, Lithuania was very close to being invaded by the Soviets in summer 1920 and being forcibly incorporated into that state, and only the Polish victory derailed this plan.
The dispute over Vilnius remained one of the biggest foreign policy issues in Lithuania and Poland. Lithuania broke off all diplomatic relations with Poland and refused any actions that would recognize Poland's control of Vilnius even de facto. For example, Lithuania broke off diplomatic relations with the Holy See after the Concordat of 1925 established an ecclesiastical province in Wilno thereby acknowledging Poland's claims to the city. Poland refused to formally recognize the existence of any dispute regarding the region, since that would have lent legitimacy to the Lithuanian claims. Railroad traffic and telegraph lines could not cross the border, and mail service was complicated. For example, a letter from Poland to Lithuania needed to be sent to a neutral country, repackaged in a new envelope to remove any Polish signs, and only then delivered to Lithuania. Despite several attempts to normalize the relations, the situation of "no war, no peace" lasted until Poland demanded to reestablish diplomatic relations by issuing the ultimatum of 1938. These tensions were one of the reasons why Józef Piłsudski's Międzymorze federation was never formed. The Soviet Union gave Vilnius to Lithuania after the Soviet invasion of Eastern Poland in September 1939.