An unstable Europe

The period immediately after the end of the First World War saw a series of wars break out across Europe, some of which were intertwined with other conflicts. The Polish-Lithuanian war is one such example, being viewed differently depending on the perspective or viewpoint of the commentator. Lithuanian historians consider this conflict part of the Lithuanian Wars of Independence whereas Polish historians consider it part of the wider Polish-Soviet War. Regardless of the view, it warrants examination in its own right as it helps illustrate ongoing struggles many new countries faced upon their creation at the end of the Great War.

Simply put, the Polish-Lithuanian War was a conflict between the newly independent Lithuania and the Second Polish Republic and mainly occurred in the regions of Vilnius and Suwalki, which are located in modern day Lithuania/Belarus and Poland.

Timeline of Polish conflicts after the First World War.


On November 13, Soviet Russia renounced the Treaty of Brest-Litovsk – the separate peace treaty between Bolshevik Russia and the losing Central Powers at the end of the First World War.

The Soviets then began to advance westwards, moving into areas being vacated by the defeated German armies and with plans to establish Soviet influenced republics in these areas. This sparked off the Polish-Soviet War and the Soviet-Lithuanian War, as these fledgling countries were in no hurry to come under the Soviet influence.

After initial successes, the Soviet progress slowly ground to a halt and then they found themselves under attack from separate Polish and Lithuanian offensives. It is worth noting at this point that the relations between Poland and Lithuania were not hostile, helped no doubt by them sharing a common enemy.

The advance of Polish (blue arrows), Lithuanian/German (dark purple arrows) against the Soviet forces in early 1919. The blue line shows the Polish front in May 1920.


On April 19, 1919, the Polish Army captured Vilnius, the capital of Lithuania from the Soviets, forcing the Russian forces to retreat. The Poles hoped that Lithuania would join the ‘Intermarium’ – an idea championed by Polish Chief of State Józef Piłsudski, for a multinational federation consisting of Poland, Lithuania, Belarus, Ukraine, and Latvia.

However, this idea clashed with the Lithuanians own wishes to remain an independent republic, seeing the Intermarium as a threat to their existence. Relations started to sour between the two countries at this point and in an attempt to head off another conflict breaking out, the Entente created demarcation lines in an effort to rein in both countries.

Foch Line

The first demarcation line was created on June 18th and was based on the current military situation rather than any ethnic or political considerations. Neither side were happy with it though as it would require the Poles to withdraw their forces a considerable distance and the Lithuanians were unhappy as it left their capital city, Vilnius, under Polish control. Subsequently, both sides ignored this line.

A second line – named the ‘Foch Line’ – after its creator Ferdinand Foch, was set up on July 18th but this line favoured the Poles more, leaving more land, including the ethnically mixed Suwalki region (According to Russian statistics from 1889, there were 57.8% Lithuanians, 19.1% Poles, and 3.5% Belarusians in the Suwałki Governorate), under their control.

However, it still required both sides to withdraw their troops so once again, neither side was happy. The attempts to resolve tension with demarcation lines had failed.

Ferdinand Foch

Various proposals for the Polish-Lithuanian border after World War I. Foch Line in dark green, modern borders in pink.

Clash at Sejny and the attempted coup.

The Poles and Lithuanians then clashed at Sejny after the Lithuanians refused to pull back all the way to their side of the new border, as determined by the Foch Line. This resulted in an uprising by the local Polish community and a short but violent series of skirmishes between the two forces, before a ceasefire was arranged and the Lithuanians agreed to withdraw to their side of the new border.

Meanwhile, the Poles – led by Józef Piłsudski - had been planning a coup d'état since July of the same year, plotting to overthrow the Lithuanian government which would result in Lithuania agreeing to becoming part of the Intermarium. However, the coup attempt failed before it could properly be launched, as Lithuanian intelligence services had got wind of the plan and intervened to prevent it occurring which in turn, further soured relations between the two countries.

Entrenched Lithuanian infantry during the Polish-Lithuanian war.

Border skirmishes

From September 1919 – June 1920, there were a series of minor skirmishes border skirmishes as both countries sought to assert their dominance in the area. Polish troops attacked Gelvonai on 19 September. Several small but violent battles flared up around the strategically important bridge over the Šventoji River.

In October, while the main Lithuanian forces were diverted to face the advancing Bermontian forces in north-western Lithuania, the Poles took the opportunity to step up their efforts and were rewarded with the capture of Salakas on 5 October. This tit for tat conflict continued even after the front line stabilised, with harassment of border guards or unwelcome incursions into villages now becoming the norm.

In March 1920, the Poles again launched an attack, targeting the area surrounding the railroad stations in Kalkūni and Turmantas. By now, the Entente, presumably growing tired of this incessant and violent bickering between two countries, were sending observers to report on what was happening, although it is unclear what action they may have intended to take. The fighting died down when the majority of Polish troops were diverted to fight in the more significant Polish-Soviet war.

The constant fighting had taken its toll on Lithuania who now faced a series cash flow problem. Its overall, yearly revenue in 1919 was 72 million marks, but it had spent – thanks to the near perpetual fighting with Poland - 190 million marks. Almost three times the amount. Unable to easily access loans or financial assistance, the Lithuanians were forced to reduce their army in size from 40,000 to 25,000 men – just a time when they might need them the most.

Map of the Suwałki Region. Its many forests and lakes complicated the military actions.

Diplomatic developments

With Poland now entwined in the Polish-Soviet war an opportunity arose for the Lithuanians. Being pushed back by the Soviet forces, the Poles asked for international assistance to prevent Poland itself being swallowed up by the Russians. At the Spa Conference in 1920 – it was decided by the Supreme War Council (set up in the First World War and consisting of Britain, France, Italy, the US and Japan) that the Polish forces would pull back behind the Curzon Line (the demarcation line between Poland and Russia) and the Russian forces would stop 50km east of it. The Lithuanians would then take back control of their capital city, Vilnius, despite protests from the Poles.

The Soviets and Lithuanians – who had also been fighting up until this point – negotiated a separate peace treaty which was signed on 12 July 1920 and in which Russia recognised Lithuanian independence and withdrew any territorial claims.

Lithuanian Army troops enter Cathedral SquareVilnius

Territorial changes

With Polish forces being slowly pushed out of Lithuanian territories by the advancing Russians, the Lithuanians took the opportunity to reclaim what they felt was rightfully theirs. In quick succession, between 7 – 13 July, they retook Turmantas, Tauragnai, Alanta, Širvintos, Musninkai, Kernavė, Molėtai, Giedraičiai, Maišiagala and Pabradė. Additionally, the Poles elected to obey the terms of the Spa Conference and transferred control of the Lithuanian capital, Vilnius, back to the Lithuanians, although by the time the Lithuanians arrived on the 15 July, the Russians had already beaten them to it, and for a while it looked as if they might try to launch their own coup against the Lithuanian government and re-establish the Lithuanian Soviet Socialist Republic (LSSR), a short-lived Soviet backed puppet state, instead.

The Lithuanians continued to reclaim lost territories in the Suwalki region over the next few days and between 17 July to 8 August, regained control of Druskininkai, Vištytis, Punsk, Giby, Seiny, Suwalki and Augustów. The Poles, conscious of being caught and trapped by the pursuing Russian forces were quick to vacate these areas and withdrew towards Łomża. With a significant amount of territory back in Lithuanian hands, they now started to organise themselves in these areas.

Polish soldiers, 1920.

Lithuanian neutrality

Tensions between Lithuania and Poland intensified again when Poland claimed that Lithuania – officially neutral in the Polish-Soviet war – was actually an ally of the Russians.

This accusation was understandable given a secret clause in the Soviet-Lithuanian peace treaty allowed the Russians free and unrestricted movement of military forces in Lithuania – something which would be of a major concern to Poland.

To be fair to Lithuania, there was little else they could do as they lacked the military might to prevent the Soviets from doing this and while the Soviets and Poles were fighting, the Russians would not want to withdraw troops from the area.

Lithuanian military enters Vilnius 

Lithuanian Special Archives

This did lead to uneven treatment towards Russian and Polish troops in Lithuania, with the Lithuanians imprisoning over a hundred Polish officers and several thousand soldiers, while Russian troops could move around the country unmolested. More seriously though was the accusation that Lithuanians had actively taken part in military operations with the Russians against the Poles, although this was never proven.

Inevitably, this breakdown in relations between Poland and Lithuania sparked off more clashes in the Suwalki region. The Poles claiming that it demonstrated how the Lithuanian government was under the control of the Russians while the Lithuanians themselves responded that they were just defending their borders.

Russian setbacks

The ongoing Polish-Soviet war saw a dramatic defeat for the Russians in August 1920 at the Battle of Warsaw. This led to the Russians returning control of Vilnius to the Lithuanians as they withdrew from the region. With their capital now fully back in their hands, the Lithuanians planned to secure their borders. Keen to avoid further conflict (and aware of the previous accusations levelled at them by the Poles), the Lithuanians attempted to maintain a strict neutrality and intern any Russian or Polish solider who encroached on their territory.

However, the Poles wanted to transport troops through Lithuanian territory and demanded that Lithuanian troops were withdrawn from the Suwalki region behind the Curzon line. For their part, the Lithuanians refused to discuss military matters without a clearly defined and agreed upon Polish-Lithuanian border. Once again, tensions rose, and the negotiations broke down.

Battle of Sejny

Once again, the strategically important Suwalki region was the scene of more conflict as brigadier general Edward Rydz-Śmigły ordered the Poles to launch a surprise attack on 28 August. The Lithuanians were caught off guard and retreated in disarray as the Poles quickly captured Augustów. By 31 August, the Lithuanians had been forced out of the Suwalki and Sejny regions completely but advancing Polish forces.

The Lithuanians reorganised and counterattacked on 2 September, with 7000 soldiers organised into 11 battalions, the goal being to capture the Augustów–Lipsk–Hrodna line and secure their border. The Lithuanian forces managed to push the Poles back, capturing Sejny and Lipsk and two days later, found themselves on the outskirts of Augustów itself.

Edward Rydz-Śmigły

In response, the Poles attacked again on 5 September and forced the Lithuanians to retreat once more and on the 9 September, they recaptured Sejny, but the Lithuanians fought back and regained Sejny and Giby. As before, fighting between Poles and Lithuanians had degenerated into tit-for-tat, relatively small-scale yet violent conflicts with neither side being able to achieve dominance and control of towns frequently changing hands.


Negotiations between the Poles and Lithuanians on 16 September, although prior to this, the Poles had been secretly planning an attack on the Russians at Niemen River which would take them through Lithuanian territory – something which they attempted to keep secret from the Lithuanians. The negotiations themselves lasted just two days before falling apart with neither side in agreement.

The League of Nations attempted to intervene and urged both sides to cease hostilities and respect the Curzon Line in a resolution issued on 20 September. Poland was urged to respect Lithuanian neutrality (and stop trying to move its troops through its territory) if the Soviets agreed to do the same. The Lithuanians agreed but the Poles reserved the right to respond militarily if deemed necessary (i.e., in response to a Russian threat) – which would include troop movement through Lithuanian territory.  

Polish forces manoeuvred through the Lithuanian front line (in pink) to the rear of Soviet troops.

Battle of Niemen River

Although a major battle in the Polish-Soviet war, the Lithuanians found themselves dragged into it when Polish forces once again travelled through Lithuanian territory in order to outflank the Russians near Hrodna and Lina. On 22 September, a large Polish force attacked a smaller Lithuanian one, once in the Suwalki region, and overwhelmed the defenders, taking around 1,700-2000 prisoners. The Poles captured important bridges over the Neman and captured the town of Sejny after a six-hour battle.

The Poles then continued their advance as the Russians retreated and leaving the Lithuanians in disarray. The attack had drastically changed the strategic situation and the Lithuanians now found their capital, Vilnius, once again vulnerable to attack – and the Poles were indeed planning on capturing the capital and using it as a bargaining tool in negotiations. For their part, the Lithuanians, desperate to retain control of their capital, were ready to give up their claims to the hotly contested Suwalki region, in return for guarantees that they would retain Vilnius.

Troops  dug in during the battle of Nieman River.

The Suwałki Agreement

Negotiations began on the evening of 29 September 1920. The Polish delegation was led by colonel Mieczysław Mackiewicz. The Lithuanian delegation was led by general Maksimas Katche. A partial ceasefire had been agreed but fighting still continued to the east of the Neman river in the Suwalki region.

One of the sticking points to the negotiations was the railway stations at Varėna. Lithuania needed access to be able to move its forces quickly – especially in regard to being able to defend Vilnius. The Poles actually captured Varėna on 6 October, which resulted fighting in the east coming to a halt.

The other main point of contention was the location of the demarcation line. The Lithuanians wanted a longer one to help shield Vilnius, the Poles wanted a shorter one to help with their planned attack on the same city. Vilnius itself was not an official subject for debate and was never directly mentioned in negotiations – but it was clearly a factor in both sides thinking.

With help from a neutral party, a French colonel Pierre Chardigny, both sides were finally able to come to an agreement. The treaty itself made no reference to Vilnius and the ceasefire was effective only along the actual demarcation line which stretched from the Suwalki region to Bastuny railway station. So, the line was incomplete, did not protect Vilnius but just indicated that it would remain on the Lithuanian side. So, the possibility that Vilnius could be captured by Polish forces remained.

Polish (left) and Lithuanian (right) delegates at the negotiation table during the Suwałki Conference.

Żeligowski's Mutiny

The day after the Suwalki agreement was finalised and a chance for peace seemed at least possible, everything fell apart. A Polish General, Lucjan Żeligowski staged a mutiny (which had been secretly planned and agreed to by the Polish Government) and invaded and captured Vilnius in what became known as Żeligowski's Mutiny.

Żeligowski then created the Republic of Central Lithuania with Vilnius as its capital and fighting continued in the region as the Lithuanians attempted to respond. Although a ceasefire soon followed, the League of Nations were unable to resolve the situation, with Poland claiming that Żeligowski acted alone. Reluctant to take military action, the League was unable to effectively intervene, even when this new ‘republic’ was then incorporated into Poland in 1923. Lithuania had lost their capital city.  

Unsurprisingly, this almost irreparably destroyed relations between Lithuania and Poland, with the Lithuanians severing all diplomatic ties with Poland and only reclaiming Vilnius in 1939.

General Lucjan Żeligowski


Lithuanian military enters Vilnius / Lithuanian Special Archives

Wulfstan - Own work, using programm InkScape

Nacionalinis M. K. Čiurlionio dailės muziejus via LIMIS (inventory number: ČDM ŽFp 1721)

Lietuvos centrinis valstybės archyvas, Lietuvos žinios, 2010 spalio 29 d.

Lonio17 (Battle of Nieman River map)

Česlovas Laurinavičius

Lithuania marks 80 years since bittersweet victory of regaining Vilnius – photos - LRT