1919 Polish coup d ' état attempt in Lithuania The Polish coup d ' état attempt in Lithuania refers to a failed attempt by Polish statesman Józef Piłsudski to overthrow the existing Lithuanian government of Prime Minister Mykolas Sleževičius , and install a pro - Polish cabinet that would agree to a union with Poland . The Polish intelligence agency , the Polish Military Organization ( PMO ) was to carry out the coup d ' état , planned to be implemented in August 1919 . The coup was designed to seem to be an initiative by local Lithuanians aiming to free their government of German influence . The PMO hoped to rely on the assistance of sympathetic Lithuanian activists . They were thwarted by the lack of cooperation and the unwillingness of sufficient number of Lithuanians to support the Polish cause . After the Sejny Uprising , a Polish revolt against the Lithuanian authorities in one of the disputed border regions , Lithuanian intelligence intensified its investigation of the Polish minority and sympathizers in Lithuania , and uncovered the planned coup . The Lithuanians , not knowing the membership of the PMO , arrested numerous Polish activists and destabilized the PMO network enough to prevent the coup attempt . Later the full membership list was obtained and the PMO in Lithuania was dissolved . The coup further strained Polish – Lithuanian relations . Background . Poland and Lithuania formed one state , the Polish – Lithuanian Commonwealth , from the Union of Lublin in 1569 to the Third Partition in 1795 . Both Poland and Lithuania regained their independence in the aftermath of World War I , but both soon became engaged in territorial disputes over the Suwałki and Vilnius Region s . During the Polish – Soviet War , Poland launched an offensive against the Soviet Union and captured Vilnius ( Wilno ) during the Vilna offensive in April 1919 . Lithuanians described Vilnius as their historical capital and an integral part of the ethnographic Lithuania , while to the Poles , because of its large Polish population , it was a Polish city . Poland ' s Chief of State Józef Piłsudski sought a union with Lithuania in hopes of reviving the old Polish – Lithuanian Commonwealth ( see Międzymorze federation ) . The Lithuanians believed they would lose their sovereignty under the proposed federation and wanted their own national state . Although Polish – Lithuanian relations were not immediately hostile , they grew worse as each side refused to compromise . As tensions rose , Lithuania asked the Allied Supreme Council to intervene , and it proposed two demarcation lines to prevent open hostilities , drawn in June and July 1919 ( the second one was known as the Foch Line ) . However , Poland ignored both lines and advanced deeper into the Lithuanian - controlled territory . Faced with pressure from the Entente , Polish Chief of State Józef Piłsudski , who was significantly involved in planning of the coup , did not want open Polish – Lithuanian hostilities , which could led to much bloodshed and even greater tensions between Poland and Lithuania . Instead , since he thought there were enough Polish sympathizers in Lithuania to stage a coup d ' état , he decided to plan one to topple the Lithuanian government . Preparations . The planning began mid - July , 1919 . At the time Poland signed a ceasefire in the Polish – Ukrainian War ; Lithuania was invaded by the Bermontians from the north and the Saxon Volunteers were leaving the Lithuanian Army . Piłsudski was planning to use a network of the Polish Military Organization ( PMO ) , an underground organization he created during World War I for diversionary and intelligence operations - like purposes . On July 31 , Piłsudski and Polish diplomat Leon Wasilewski arrived at Vilnius , then controlled by Poland . Piłsudski ' s visit had no clear explanation . He later said that he arrived to negotiate with Lithuanians , led by Augustinas Voldemaras , while Lithuanian historian Vytautas Lesčius suggests he was holding talks with pro - Polish estate owners from the Vilnius Region . On August 3 , Wasilewski arrived at Kaunas , the temporary capital of Lithuania , to negotiate with Prime Minister Mykolas Sleževičius . The Polish mission declared that Poland had no plans to annex Lithuania and proposed a plebiscite in the contested territories , allowing local inhabitants to determine their future . The Lithuanians replied that the disputed territories were an integral part of Lithuania and rejected the idea of a plebiscite . Negotiations broke down and Wasilewski left Kaunas on August 7 . The negotiations were then used to evaluate viability of the coup , the preparedness of the PMO , and the attitude of Lithuanian diplomats towards a union with Poland . After the failure Wasilewski ' s diplomatic mission , Polish newspapers increased their anti - Lithuanian propaganda . They said that the Council of Lithuania was a pro - German puppet , ignoring popular wishes for a union with Poland as such union would break German influence in the state . The Polish media further reported on growing anti - government sentiment among the Lithuanians . This information was in line with the Polish plans to present the coup as an initiative by the local population to free Lithuania from German domination . While the plotters counted on military intervention by regular Polish troops , the Polish government maintained it had not inspired the coup . The official goal of the Polish plan was to " 1 ) create an independent Lithuania , powerful , truly democratic , connected voluntarily with Poland in a union , with as much internal autonomy as possible and 2 ) acceptance of the Polish minority in Lithuania as a partner in the Lithuanian government and recognition of the Polish language as equal to the Lithuanian language in Lithuania . " The PMO recruited Lithuanian activists Stanisław Narutowicz , Juozas Gabrys , Jurgis Aukštuolaitis , and Klemensas Vaitiekūnas . On August 20 – 22 , 1919 , Wasilewski and Tadeusz Kasprzycki together with Narutowicz and Aukštuolaitis planned out the coup details . During the coup , scheduled for the night from August 28 to 29 , the rebels were to capture Kaunas and hold it until the arrival of the Polish regular units invited to protect the city . The Council of Lithuania and the Lithuanian government was to be deposed and replaced by a pro - Polish cabinet . General Silvestras Žukauskas was to be installed as a military dictator of the new Lithuanian government , with Aukštuolaitis as his second - in - command and Narutowicz as the head of the civilian government . General Žukauskas , then chief commander of the Lithuanian forces , was not aware of the coup , but was known for his generally friendly attitude towards Poland and was expected to support the aftermath . Other posts were reserved for Mykolas Biržiška , Jonas Vileišis , Steponas Kairys , Juozas Tūbelis and others , similarly unaware of the coup . Aukštuolaitis was given 800 , 000 and promised another 300 , 000 German mark s to finance the coup . Coup discovered . Eventually , the uprising was doomed by poor communication and the overeagerness of some of the PMO activists . Piłsudski failed to discourage local PMO activists from carrying out the Sejny Uprising in the Suwałki Region . The local PMO disregarded his recommendations and launched the uprising , which while locally successful , led to the failure of the nationwide coup . PMO members in Lithuania stated that the Sejny uprising had damaged their reputation , and many of its former supporters rejected calls by PMO recruiters . The initial coup was postponed to September 1 , 1919 . However , some PMO units began their actions ( cutting telegraph wires , damaging railways , etc . ) as scheduled previously – on the night of August 27 to 28 . The Lithuanian intelligence intercepted and decoded the order to delay the coup . They had known before that Poles were plotting , but did not know who and when . The Lithuanian government was informed about the cut telegraph wires and intercepted order in the morning of August 28 . However , the government did not consider the threat real and did not take appropriate action . A group of 18 Lithuanian Army officers , with tacit approval from Sleževičius , took the initiative . Afraid that PMO members infiltrated the military , they secretly decided to begin mass arrests of Polish supporters on the night from August 28 to 29 . Since they did not know who exactly was behind the conspiracy , the Lithuanians arrested more prominent Polish activists in Kaunas . Several dozen Poles were arrested the first night , including Aukštuolaitis and 23 Polish officers serving in the Lithuanian Army . By the second night the number of arrested Poles grew to 200 . Kaunas was declared under a state of siege . The Polish press noted mass arrests of Polish activists " to whom no charge can be ascribed other than being Poles " and concluded that this was proof of the systematic anti - Polish policies of the German - ridden Lithuanian government . Because the Lithuanians did not have a list of PMO members , they did not arrest the main leaders . Also , provincial PMO branches remained intact . Therefore , on September 17 , 1919 , new orders were issued scheduling the second coup attempt for the end of September . This attempt was also discovered . A Lithuanian woman succeeded in convincing Petras Vrubliauskas , PMO deputy commander in Vilnius , to transfer the PMO document archive to the Lithuanians . On September 21 , the Lithuanians obtained a full list of PMO members and supporters and arrested them in the following days . The PMO branch in Lithuania ceased to function and was liquidated . Aftermath and evaluation . The Lithuanians charged 117 persons during a military trial on December 11 – 24 , 1920 . Six leaders received life sentences . Other sentences ranged from 15 years to 8 months in prison . At least 15 individuals were acquitted . By 1928 there were no PMO members in Lithuanian prisons : some were exchanged for Lithuanian prisoners or released early . General Žukauskas was removed from his post as the commander of the Lithuanian Army and had to battle the perceived friendliness to Poland for much of his further career . The Polish government initially denied that there was any coup ; later it admitted that locals planned an uprising , but claimed it had no part in it . The coup further strained the Polish – Lithuanian relations , making Lithuanians even more uncompromising and afraid of Polish annexation . The planned coup was criticized by historians as unrealistic for the following reasons . Piłsudski ' s plan was based on false assumptions and faulty intelligence , which incorrectly indicated that the Sleževičius government was deeply unpopular , and that the general Lithuanian population was relatively friendly to Poland . No notable ethnic Lithuanian politicians declared support for the plan ; the plan relied on support from General Žukauskas , but his support was never confirmed ; Narutowicz , who was to head the civilian government , was a Pole ; the PMO was weak and incapable of taking control if the coup met any significant resistance ; and intervention of the Polish army would have led to bloodshed and undermined the idea of a voluntary union or alliance with Poland . The only group that supported the coup was the Polish minority in Lithuania , increasingly alienated by Lithuanian government policies . However , according to the Lithuanian census of 1923 , the minority constituted 3 . 2 % of the population outside the Vilnius Region . On the ground , the uprising was doomed by poor communication and the overeagerness of some of the PMO activists .