Territorial evolution of Poland Poland ( ) is a country in Central Europe bordered by Germany to the west ; the Czech Republic and Slovakia to the south ; Ukraine , Belarus and Lithuania to the east ; and the Baltic Sea and Kaliningrad Oblast , a Russian exclave , to the north . The total area of Poland is , making it the 69th largest country in the world and the ninth largest in Europe . From a nucleus between the Odra and Vistula rivers on the North European Plain , Poland has at its largest extent expanded as far as the Baltic , the Dnieper , the Black Sea and the Carpathians , while in periods of weakness it has shrunk drastically or even ceased to exist . Territorial history . In 1492 , the territory of Poland - Lithuania - not counting the fiefs of Mazovia , Moldavia and East Prussia - covered , making it the largest territory in Europe ; by 1793 it had fallen to , the same size as Great Britain , and in 1795 it disappeared completely . The first 20th century incarnation of Poland , the Second Polish Republic , occupied while since 1945 , a more westerly Poland covered . The Poles are the most numerous of the West Slavs and occupy what some believe to be the original homeland of the Slavic peoples . While other groups migrated , the Polanie remained " in situ " along the Vistula , from the river ' s sources to its estuary at the Baltic Sea . There is no other European nation centred to such an extent on one river . The establishment of a Polish state is often identified with the adoption of Christianity by Mieszko I in 966 CE ( see Baptism of Poland ) , when the state covered territory similar to that of present - day Poland . In 1025 CE , Poland became a kingdom . In 1569 , Poland cemented a long association with the Grand Duchy of Lithuania by signing the Union of Lublin , forming the Polish – Lithuanian Commonwealth . The Polish – Lithuanian Commonwealth was one of the largest and most populous countries in 16th - and 17th - century Europe . The Polish - Lithuanian Commonwealth had many characteristics that made it unique among states of that era . The Commonwealth ' s political system , often called the Noble ' s Democracy or Golden Freedom , was characterized by the sovereign ' s power being reduced by laws and the legislature ( Sejm ) , which was controlled by the nobility ( szlachta ) . This system was a precursor to the modern concepts of broader democracy and constitutional monarchy . The two comprising states of the Commonwealth were formally equal , although in reality Poland was a dominant partner in the union . Its population was hallmarked by a high level of ethnic and confessional diversity , and the state was noted for having religious tolerance unusual for its age , although the degree of tolerance varied over time . In the late 18th century , the Polish - Lithuanian Commonwealth began to collapse . Its neighbouring states were able to slowly dismember the Commonwealth . In 1795 , Poland ' s territory was completely partitioned among the Kingdom of Prussia , the Russian Empire , and Austria . Poland regained its independence as the Second Polish Republic in 1918 after World War I , but lost it in World War II through occupation by Nazi Germany and the Soviet Union . Poland lost over six million citizens in World War II , emerging several years later as the socialist People ' s Republic of Poland within the Eastern Bloc , under strong Soviet influence . During the Revolutions of 1989 , communist rule was overthrown and Poland became what is constitutionally known as the " Third Polish Republic . " Poland is a unitary state made up of sixteen voivodeships ( ) . Poland is a member of the European Union , NATO , and the Organisation for Economic Co - operation and Development ( OECD ) . Poland currently has a population of over 38 million people , which makes it the 34th most populous country in the world and one of the most populous members of the European Union . Territorial timeline . In the period following the emergence of Poland in the 10th century , the Polish nation was led by a series of rulers of the Piast dynasty , who converted the Poles to Christianity , created a sizeable Central Europe an state , and integrated Poland into European culture . Formidable foreign enemies and internal fragmentation eroded this initial structure in the 13th century , but consolidation in the 14th century laid the base for the Polish Kingdom . Beginning with the Lithuanian Grand Duke Jogaila , the Jagiellon dynasty ( 1385 – 1569 ) ruled the Polish - Lithuanian Union . The Lublin Union of 1569 established the Polish - Lithuanian Commonwealth as an influential player in European politics and a vital cultural entity . Duchy of Prussia . In 1525 , during the Protestant Reformation , the Grand Master of the Teutonic Knights , Albert of Hohenzollern , secularized the order ' s Prussian territory , becoming Albert , Duke of Prussia . His duchy , which had its capital in Königsberg , was established as a fief of the Crown of Poland . 992 . Mieszko I of Poland was the first historical ruler of Poland . He was responsible for the introduction and subsequent spread of Christianity in Poland . During his long reign most of the territories inhabited by Polish tribes of West Slavs were united into a single Polish state . The last of his conquests were Silesia and Lesser Poland that were incorporated some time before 990 . 1025 . During the reign of Bolesław ' s the Brave , relations between Poland and the Holy Roman Empire deteriorated , resulting in a series of wars ( 1002 – 1005 , 1007 – 1013 , 1015 – 1018 ) . From 1003 – 1004 Bolesław intervened militarily in Czech dynastic conflicts . After his forces were removed from Bohemia in 1018 , Bolesław retained Moravia . In 1013 the marriage between Bolesław ' s son Mieszko and Richeza of Lotharingia , the niece of Emperor Otto III and future mother of Casimir I the Restorer , took place . The conflicts with Germany ended in 1018 with the Peace of Bautzen accord , on favorable terms for Bolesław . In the context of the 1018 Kiev expedition , Bolesław took over the western part of Red Ruthenia . In 1025 , shortly before his death , Bolesław I the Brave finally succeeded in obtaining the papal permission to crown himself , and became the first king of Poland . 1050 . The first Piast monarchy collapsed after the death of Boleslaw ' s son - king Mieszko II in 1034 . Deprived of a government , Poland was ravaged by an anti - feudal and pagan rebellion , and in 1039 by the forces of Bretislaus I of Bohemia . The country suffered territorial losses , and the functioning of the Gniezno archdiocese was disrupted . After returning from exile in 1039 , Duke Casimir I ( 1016 – 1058 ) , properly known as the Restorer have rebuilt the Polish monarchy and the country ' s territorial integrity through several military campaigns : in 1047 , Masovia was taken back from Miecław , and in 1050 Silesia from the Czechs . Casimir was aided by the recent adversaries of Poland , the Holy Roman Empire and Kievan Rus ' , both of whom disliked the chaos in Poland . Casimir ' s son Bolesław II the Generous managed to restore most of the countries strength and influence and was able to crown himself king in 1076 . In 1079 there was an anti - Bolesław conspiracy or conflict that involved the Bishop of Kraków . Bolesław had Bishop Stanislaus of Szczepanów executed ; subsequently Bolesław was forced to abdicate the Polish throne because of the pressure from the Catholic Church and the pro - imperial faction of the nobility . The rule over Poland passed into the hands of his younger brother Władysław Herman . 1125 . After a power struggle , Bolesław III the Wry - mouthed ( son of Władysław Herman , ruled 1102 – 1138 ) became the Duke of Poland by defeating his half - brother in 1106 – 1107 . Bolesław ' s major achievement was the reconquest of all of Mieszko I ' s Pomerania , a task begun by his father and completed by Bolesław around 1123 . Szczecin was subdued in a bloody takeover and Western Pomerania up to Rügen , except for the directly incorporated southern part , became Bolesław ' s fief , to be ruled locally by Wartislaw I , the first duke of the Griffin dynasty . At this time , Christianization of the region was initiated in earnest , an effort crowned by the establishment of the Pomeranian Wolin Diocese after Bolesław ' s death in 1140 . 1145 . The Testament of Bolesław III Krzywousty was a political act by the Piast duke Bolesław III Wrymouth of Poland , in which he established rules for governance of the Polish kingdom by his four surviving sons after his death . By issuing it , Bolesław planned to guarantee that his heirs would not fight among themselves , and would preserve the unity of his lands under the House of Piast . However , he failed ; soon after his death his sons fought each other , and Poland entered a period of fragmentation lasting about 200 years . 1238 . In the first half of the 13th century Silesian duke Henry I the Bearded , reunited much of the divided Kingdom of Poland ( " Regnum Poloniae " ) . His expeditions led him as far north as the Duchy of Pomerania , where for a short time he held some of its southern areas . He became the duke of Kraków ( Polonia Minor ) in 1232 , which gave him the title of senior duke of Poland ( see Testament of Bolesław III Krzywousty ) , and came into possession of most of Greater Poland in 1234 . Henry failed in his attempt to achieve the Polish crown . His activity in this field was continued by his son and successor Henry II the Pious , until his sudden death in 1241 ( Battle of Legnica ) . His successors were not able to maintain their holdings outside of Silesia , which were lost to other Piast dukes . Polish historians refer to territories acquired by Silesian dukes in this period as " Monarchia Henryków śląskich " ( " The monarchy of the Silesian Henries " ) . In those days Wrocław was the political center of the divided Kingdom of Poland . 1248 . Few years after the death of Henry II the Pious his son - Bolesław II the Bald - sold the northwest part of his duchy - the Lubusz Land - to the to Magdeburg ' s Archbishop Wilbrand von Käfernburg and the Ascanian margraves of Brandenburg . This had far reaching negative consequences for the integrity of the western border , leading to an expansion of Brandenburg possessions into the east of Odra river . As a result a wide peace of Land was annexed from Poland and Pomerania that together with Lubusz Land formed the newly established Brandenburgian province of Neumark . 1295 . In 1295 , Przemysł II of Greater Poland became the first , since Bolesław II , Piast duke crowned as King of Poland , but he ruled over only a part of the territory of Poland ( including from 1294 Gdańsk Pomerania ) and was assassinated soon after his coronation . 1300 . A more extensive unification of Polish lands was accomplished by a foreign ruler , Wenceslaus II of Bohemia of the Přemyslid dynasty , who married Przemysł ' s daughter and became King of Poland in 1300 . Václav ' s heavy - handed policies soon caused him to lose whatever support he had earlier in his reign ; he died in 1305 . 1333 - 1370 . After the death of Wenceslaus III of Bohemia - son of Wenceslaus II - in 1306 , most of the Polish Lands came under the rule of duke Władysław I the Elbow - high . However at this points , various foreign states were staking their claims on some parts of Poland . Margraviate of Brandenburg invaded Pomerelia in 1308 , leading Władysław I the Elbow - high to request assistance from the Teutonic Knights , who evicted the Brandenburgers but took the area for themselves , annexed and incorporated it into the Teutonic Order state in 1309 ( Teutonic takeover of Danzig ( Gdańsk ) and Treaty of Soldin / Myślibórz ) . This event caused a long - lasting dispute between Poland and the Teutonic Order over the control of Gdańsk Pomerania . It resulted in a series of Polish – Teutonic War s throughout 14th and 15th centuries . During this time , all Silesian dukes accepted Władysław ' s claims for sovereignty over other Piasts . After acquiring papal consent for his coronation , all nine dukes of Silesia declared twice ( in 1319 before and in 1320 after the coronation ) that their realms lay inside the borders of the Polish Kingdom . However , despite formal papal consent for the coronation , Wladyslaw ' s right to the crown was disputed by successors of Wenceslaus III ( a king of both Bohemia and Poland ) on the Bohemian throne . In 1327 John of Bohemia invaded . After the intervention of King Charles I of Hungary he left Polonia Minor , but on his way back he enforced his supremacy over the Upper Silesian Piasts . In 1329 Władysław I the Elbow - high fought with the Teutonic Order . The Order was supported by John of Bohemia who dominated the dukes of Masovia and Lower Silesia . In 1335 John of Bohemia renounced his claim in favour of Casimir the Great , who in return renounced his claims to the Silesia province . This was formalized in the Treaty of Trentschin and Congress of Visegrád ( 1335 ) , ratified in 1339 and later confirmed in the 1348 Treaty of Namslau . King Casimir , being deprived of historically and ethnically Polish lands of Silesia and Pomerelia sought a compensation of this loses in the east . Through a series of military campaigns between 1340 and 1366 Casimir had annexed the Halych – Volodymyr area of Rus ' . The city of Lwów quickly developed to become a main town of this new region . Allied with Denmark and Western Pomerania , Casimir was able to impose some corrections on the western border as well . In 1365 Drezdenko and Santok became Poland ' s fiefs , while Wałcz district was in 1368 taken outright , severing the land connection between Brandenburg and the Teutonic state and connecting Poland with Farther Pomerania . 1635 . Sweden , weakened by involvement in the Thirty Years ' War , agreed to sign the Armistice of Stuhmsdorf ( also known as Treaty of Sztumska Wieś or Treaty of Stuhmsdorf ) in 1635 , favourable to the Polish - Lithuanian Commonwealth in terms of territorial concessions . 1655 . In the history of Poland and Lithuania , the Deluge refers to a series of wars in the mid - to - late 17th century that left the Polish - Lithuanian Commonwealth in ruins . The Deluge refers to the Swedish invasion and occupation of the western half of Poland - Lithuania from 1655 to 1660 and the Khmelnytskyi Uprising in 1648 , which led to Russia ' s invasion during the Russo - Polish War . 1657 . The was a treaty signed on September 19 , 1657 , in the eastern Prussian town of Wehlau ( Welawa , now Znamensk ) between Poland and Brandenburg - Prussia during the Swedish Deluge . The treaty granted independence to Prussia in recognition of its help against the Swedish forces during the Deluge . 1660 . In the , the Polish King , John II Casimir , renounced his claims to the Swedish crown , which his father Sigismund III Vasa had lost in 1599 . Poland formally ceded Swedish Livonia and the city of Riga , which had been under de facto Swedish control since the 1620s . The signing of the treaty ended Swedish involvement in the Deluge . 1667 . The ended with the of January 13 , 1667 . The peace settlement gave Moscow control over the so - called with the Polish Commonwealth retaining Right - bank Ukraine . The signing of the Treaty ended Russian occupation of the Polish confederation and the Deluge war . Since the war started the population of the Polish - Lithuanian Commonwealth had been nearly halved by war and disease . War had destroyed the economic base of the cities and raised a religious fervour that ended Poland ' s policy of religious tolerance . 1672 . As a result of the Polish – Ottoman War the Polish commonwealth ceded Podolia in the 1672 Treaty of Buczacz . 1686 . The Eternal Peace Treaty of 1686 was a treaty between the Tsardom of Russia and the Polish - Lithuanian Commonwealth signed on May 6 , 1686 , in Moscow . It confirmed the earlier Truce of Andrusovo of 1667 . The treaty secured Russia ' s possession of the Left - bank Ukraine , Zaporozh ' ye , Seversk lands , the cities of Chernihiv , Starodub , and Smolensk and its outskirts , while Poland retained Right - bank Ukraine . 1699 . The Treaty of Karlowitz , or Treaty of Karlovci , was signed on January 26 , 1699 , in Sremski Karlovci , a town in modern - day Serbia . The Treaty of Karlowitz was signed following a two - month congress between the Ottoman Empire and the Holy League of 1684 , a coalition of various European powers including the Habsburg Monarchy , the Polish - Lithuanian Commonwealth , the Republic of Venice , and the Russia of Peter I Alekseyevich . The treaty concluded the Austro - Ottoman War of 1683 – 1697 , in which the Ottoman side had finally been defeated at the Battle of Senta . The Ottomans ceded most of Hungary , Transylvania , and Slavonia to Austria while Podolia returned to Poland . Most of Dalmatia passed to Venice , along with the Morea ( the Peloponnesus peninsula ) and Crete . 1772 . In February 1772 , an agreement for the partition of the Polish - Lithuanian Commonwealth was signed in Vienna . Early in August Russian , Prussian and Austrian troops simultaneously entered the Commonwealth and occupied the provinces agreed upon among themselves . By the first partition in 1772 , the Polish - Lithuanian Commonwealth lost about ( 30 % of its territory , amounting at that time to about ) , with a population of over four to five million people ( about a third of its population of 14 million before the partition ) . 1793 . By the 1790s the First Polish Republic had deteriorated into such a helpless condition that it was successfully forced into an unnatural and ultimately deadly alliance with its enemy , Prussia . The alliance was cemented with the Polish - Prussian Pact of 1790 . The conditions of the Pact were such that the succeeding and final two partitions of Poland were inevitable . The May Constitution of 1791 enfranchised the bourgeoisie , established the separation of the three branches of government , and eliminated the abuses of Repnin Sejm . Those reforms prompted aggressive actions on the part of Poland ' s neighbours , wary of a potential renaissance of the Commonwealth . In the second partition , Russia and Prussia took so much territory that only one - third of the 1772 population remained in Poland . 1795 . Kosciuszko ' s ragtag insurgent armies , who fought to regain Polish territory , won some initial successes but they eventually fell before the superior forces of the Russian Empire . The partitioning powers , seeing the increasing unrest in the remaining Commonwealth , decided to solve the problem by erasing any independent Polish state from the map . On 24 October 1795 their representatives signed a treaty dividing the remaining territories of the Commonwealth between their three countries . 1807 . Duchy of Warsaw . Napoleon ' s attempts to build and expand his empire kept Europe at war for almost a decade and brought him into conflict with the same European powers that had beleaguered Poland in the last decades of the previous century . An alliance of convenience was the result of this situation . Volunteer Polish legions attached themselves to Bonaparte ' s armies , hoping that in return the emperor would allow an independent Poland to reappear out of his conquests . The Duchy of Warsaw was a Polish state established by Napoleon in 1807 from the Polish lands ceded by the Kingdom of Prussia under the terms of the Treaties of Tilsit . The duchy was held in personal union by one of Napoleon ' s allies , King Frederick Augustus I of Saxony . Free City of Danzig ( Napoleonic ) . Prussia had acquired the City of Danzig in the course of the Second Partition of Poland in 1793 . After the defeat of King Frederick William III of Prussia at the 1806 Battle of Jena - Auerstedt , according to the Franco - Prussian Treaty of Tilsit of 9 July 1807 , the territory of the free state was carved out from lands that made up part of the West Prussia province . 1809 . In 1809 , a short war with Austria started . Although the Duchy of Warsaw won the Battle of Raszyn , Austrian troops entered Warsaw , but Duchy and French forces then outflanked their enemy and captured Kraków , Lwów and much of the areas annexed by Austria in the Partitions of Poland . After the Battle of Wagram , the ensuing Treaty of Schönbrunn allowed for a significant expansion of the Duchy ' s territory southwards with the regaining of once - Polish and Lithuanian lands . 1815 . Following Napoleon ' s failed invasion of Russia , the duchy was occupied by Prussian and Russian troops until 1815 , when it was formally partitioned between the two countries at the Congress of Vienna . Congress Poland . Congress Poland was created out of the Duchy of Warsaw at the Congress of Vienna in 1815 , when European states reorganized Europe following the Napoleonic wars . Grand Duchy of Posen . The Grand Duchy of Posen was a region in the Kingdom of Prussia in the Polish lands commonly known as " Greater Poland " between the years 1815 – 1848 . According to the Congress of Vienna it was to have autonomy . In practice it was subordinated to Prussia and the proclaimed rights for Poles were not respected . The name was unofficially used afterwards for denoting the territory , especially by Poles , and today is used by modern historians to describe different political entities until 1918 . Its capital was Posen ( Polish : Poznań ) . Free City of Kraków . The Free , Independent , and Strictly Neutral City of Kraków with its Territory , more commonly known as either the Free City of Kraków or Republic of Kraków , was a city - state created by the Congress of Vienna in 1815 . 1831 . After the November Uprising , Congress Poland lost its status as a sovereign state in 1831 and the administrative division of Congress Poland was reorganized . Russia issued an " organic decree " preserving the rights of individuals in Congress Poland but abolished the Sejm . This meant Poland was subject to rule by Russian military decree . 1846 . In the aftermath of the unsuccessful Kraków Uprising , the Free City of Kraków was annexed by the Austrian Empire . 1848 . After the defeat of Congress Poland , many Prussian liberals sympathised with the demand for the restoration of the Polish state . In the spring of 1848 the new liberal Prussian government allowed some autonomy to the Grand Duchy of Posen in the hope of contributing to the cause of a new Polish homeland . Due to a number of factors , including the outrage of the German - speaking minority in Posen , the Prussian government reversed course . By April 1848 , the Prussian army had already suppressed the Polish militias and National Committees that emerged in March . By the end of the year the Duchy had lost the last vestiges of its formal autonomy , and was downgraded to a Province of the Prussian kingdom . 1918 . The West Ukrainian People ' s Republic was proclaimed on November 1 , 1918 , with Lviv as its capital . The Republic claimed sovereignty over Eastern Galicia , including the Carpathians up to the city of Nowy Sącz in the west , as well as Volhynia , Carpathian Ruthenia and Bukovina . Although the majority of the population of the Western - Ukrainian People ' s Republic were Ukrainians , large parts of the claimed territory were considered Polish by the Poles . In Lviv the Ukrainian residents supported the proclamation , the city ' s significant Jewish minority accepted or remained neutral towards the Ukrainian proclamation , and the Polish majority was shocked to find themselves in a proclaimed Ukrainian state . 1919 . Creation of Poland . In the aftermath of World War I the Polish people broke out in the Greater Poland Uprising on December 27 , 1918 , in Poznań after a patriotic speech by Ignacy Paderewski , a famous Polish pianist . The fighting continued until June 28 , 1919 , when the Treaty of Versailles was signed , which recreated the nation of Poland . From the defeated German Empire , Poland received the following : Poland seizes West Ukrainian People ' s Republic . On July 17 , 1919 , a ceasefire was signed in the Polish – Ukrainian War with the West Ukrainian People ' s Republic ( ZUNR ) . As part of the agreement Poland kept ZUNR territory . The West Ukrainian People ' s Republic then merged with the Ukrainian People ' s Republic ( UNR ) . On June 25 , 1919 , Supreme Allies Council transferred East Galicia ( ZUNR territory ) to Poland . Polish - Soviet War . The Polish – Soviet War ( February 1919 – March 1921 ) was an armed conflict between Soviet Russia and Soviet Ukraine on the one hand and the Second Polish Republic and the short - lived Ukrainian People ' s Republic on the other . The war was the result of conflicting expansionist ambitions . Poland , whose statehood had just been re - established by the Treaty of Versailles following the Partitions of Poland in the late 18th century , sought to secure territories it had lost at the time of the partitions . The aim of the Soviet states was to control those same territories , which the Russian Empire had gained in the partitions of Poland . 1920 . Free City of Danzig . The Free City of Danzig ( Gdańsk ) was created on 15 November 1920 in accordance with the terms of Article 100 ( Section XI of Part III ) of the 1919 Treaty of Versailles . As the Treaty stated , the region was to remain separated from Germany and from Poland , but it was not an independent state . The Free City was under League of Nations protection and put into a binding customs union with Poland . Poland was given full rights to develop and maintain transportation , communication , and port facilities in the city . The Free City was created in order to give Poland access to a well - sized seaport . Polish – Lithuanian War . The Polish - Lithuanian War was an armed conflict between Lithuania and the Second Polish Republic , lasting from August 1920 to October 7 , 1920 , in the aftermath of World War I , not long after both countries had regained their independence . It was part of a wider conflict over disputed territorial control of the cities of Vilnius ( ) , Suwałki and Augustów . In the aftermath of the war the Republic of Central Lithuania was created in 1920 following the staged rebellion of soldiers of the 1st Lithuanian - Belarusian Infantry Division of the Polish Army , supported by the Polish air force , cavalry and artillery . Centered on the historical capital of the Grand Duchy of Lithuania , Vilna ( , ) , for eighteen months the entity served as a buffer state between Poland , upon which it depended , and Lithuania , which claimed the area . Negotiations with Russia . Soon after the Battle of Warsaw the Bolsheviks sued for peace . The Poles , exhausted , constantly pressured by the Western governments and the League of Nations , and with its army controlling the majority of the disputed territories , were willing to negotiate . The Soviets made two offers : one on September 21 and the other on September 28 . The Polish delegation made a counteroffer on October 2 . On the October 5 , the Soviets offered amendments to the Polish offer , which Poland accepted . The armistice between Poland on the one side and Soviet Ukraine and Soviet Russia on the other was signed on October 12 and went into effect on October 18 . Long negotiations ensued , with the Treaty of Riga being signed in March 1921 . The assessment of relative advantage is not universally agreed . Russian and Polish historians tend to assign victory to their respective countries . Outside assessments vary , mostly between calling the result a Polish victory and being inconclusive . However , in his secret report to the 9th Conference of the Bolshevik Party on 20 September 1920 , Lenin called the outcome of the war " In a word , a gigantic , unheard - of defeat " Negotiations with Czechoslovakia . During the closing years of World War I Polish and Czechoslovakia n diplomats met to arrange a common border between the two new countries . By the time armistice was declared , most of the border was agreed except for three small politically sensitive areas with both Polish and Czechoslovak residents . The Cieszyn Silesia or the Duchy of Cieszyn ( and ) was a small area that the pre - World War I census showed was predominantly Polish in three districts ( Teschen , Bielsko and Frysztat ) and mainly Czech in the fourth district of Frydek . The economic importance of Cieszyn Silesia lay in the rich coal basin around Karvina and in the valuable Košice – Bohumín Railway , which linked Bohemia with Slovakia . In northern Cieszyn Silesia , the railroad junction of Bohumín ( and ) served as a crossroads for international transport and communications . Claims over these regions turned violent in 1919 with a brief military conflict , the Seven - day war , between Polish and Czechoslovak units . The Allied governments pressed for a ceasefire and on 3 February 1919 a Polish - Czech border agreement was signed on the basis of the 5 November 1918 ethnic division agreement . This was later changed at the Conference of Ambassadors in Spa , Belgium on 28 July 1920 . Cieszyn ( ) was divided along the Olza river between the two newly created states of Poland and Czechoslovakia . The smaller western suburbs of Cieszyn were joined to Czechoslovakia as the new town of Český Těšín along with the railroad and the Karvina coal basin . Poland received the portion of Cieszyn east of the Olza river . The Conference of Ambassadors divided the region just as the Red Army was nearing Warsaw . It was later learned that this award resulted from a secret deal between Edvard Beneš and French and British officials . The county of Orawa ( ) arose before the 15th century . The county ' s territory is situated along the Orava River between Zazriva and the Tatra Mountains . Spisz ( ) is situated between the High Tatras and the Dunajec River in the north , the springs of the Váh River in the west , the Slovak Ore Mountains and the Hnilec River in the south , and a line running from the town of Stara Ľubovňa , via the Branisko Mountains , to the town of Margecany in the east . While the Orawa and Spisz border was in arbitration , many groups fought to be a part of Poland , including a number of Polish authors . They began to write about an alleged three hundred thousand Poles living in the Orawa territory . The Conference of Ambassadors decided that Czechoslovakia would cede to Poland a number of villages from the Orawa and Spisz regions , including the municipalities of Oravy Srnie , Podvlk , Harkabúz , Nižná Zubrica , Vyšná Zubrica , Oravka , Bukovina - Podsklie , Pekelník , Jablonka , Chyžné , Hladovka , Suchá Hora , Vyšná Lipnica , a part of Nižné Lipnice and 4 . 2 % of the rather Belá new communities , with Fridman ( Falštin settlement ) , Krempach , Tribš , Durštín , Čierna Hora , Jurgov , Repiská , Vyšné lapse , Nižné lapse , Nedeca , Kacvín and Lapšanka . 1921 . In late 1921 a border adjustment between the Weimar Republic and Poland took place as a result of the Silesian Uprisings . The uprising were a series of three armed rebellions that took place between 1919 and 1921 by the Polish people in the Upper Silesia region against the Weimar Republic . The Polish people of the region wanted to join the Second Polish Republic , which had been established following World War I . The 1919 Treaty of Versailles had called for a plebiscite in Upper Silesia in 1921 to determine whether the territory should be a part of Germany or Poland . The plebiscite took place on March 20 , 1921 , two days after the signing of the Treaty of Riga , which ended the Polish - Soviet war . In the plebiscite , 707 , 605 votes were cast for Germany , and 479 , 359 for Poland . The Germans had a majority , by 228 , 246 votes . In late April 1921 , rumours flew that Upper Silesia would stay in Germany . This led to the Third Polish Uprising in May – July 1921 . The question of the Upper Silesia problem was turned over to a council of the League of Nations . The commission , consisting of four representatives — one each from Belgium , Brazil , Spain , and China . The commission gathered its own data , interviewing Poles and Germans from the region . On the basis of the reports of this commission and those of its experts , on October 1921 the Council awarded the greater part of the Upper Silesian industrial district to Poland . 1922 . After a variety of delays , a disputed election to join Poland took place on January 8 , 1922 , and the Republic of Central Lithuania became part of Poland . 1924 . The Polish government was not satisfied with the Czechoslovakia - Polish border decided from the Paris Peace Conference or from the Conference of Ambassadors . The conflict was only resolved by the Council of the League of Nations ' Permanent Court of International Justice on March 12 , 1924 , which decided that Czechoslovakia should retain the territory of Javorzyna . and which entailed ( in June of the same year ) an additional exchange of territories in Orava - the territory around Lipnica Wielka ( Nižná Lipnica ) went to Poland , the territory around Suchá Hora ( Sucha Gora ) and Hladovka ( Glodowka ) went to Czechoslovakia . 1938 . As Czechoslovakia was being absorbed into the German Reich , Zaolzie , the Czech half of Cieszyn , was annexed by Poland in 1938 following the Munich Agreement and the First Vienna Award . At noon on September 30 , Poland gave an ultimatum to the Czechoslovak government . It demanded the immediate evacuation of Czech troops and police from Zaolzie and gave Prague until noon the following day . At 11 : 45 a . m . on October 1 the Czech foreign ministry called the Polish ambassador in Prague and told him that Poland could have what it wanted . Poland was accused of being an accomplice of Nazi Germany – a charge that Warsaw was hard put to deny . Poland seized land from northern Spisz and northern Orawa , including territories around Suchá Hora and Hladovka , around Javorina , around Leśnica in the Pieniny Mountains , a small territory around Skalité , and some other very small border regions . They officially received the territories on 1 November 1938 . Polish military groups began to carry out assimilation of the population . Polish was introduced as the only official language and the Slovak Intelligence were displaced from the territories . 1939 . World War II . In 1939 , Germany and the Soviet Union invaded Poland and partitioned it pursuant to the Molotov - Ribbentrop Pact . After the invasion , Germany annexed the lands it lost to reformed Poland in 1919 – 1922 by the Treaty of Versailles : the Polish Corridor , West Prussia , the Province of Posen , and parts of eastern Upper Silesia . The council of the Free City of Danzig voted to become a part of Germany again , although Poles and Jews were deprived of their voting rights and all non - Nazi political parties were banned . Parts of Poland that had not been part of Wilhelmine Germany were also incorporated into the Reich . Two decrees by Adolf Hitler ( October 8 and October 12 , 1939 ) provided for the division of the annexed areas of Poland into the following administrative units : These territories had an area of and a population of 10 , 000 , 000 people . The remaining Polish territory was annexed by the Soviet Union or made into the German - controlled General Government occupation zone . Eastern areas of Poland became part of either Soviet Belarus ( including Białystok , Łomża , Baranowicze and Brest ) or Soviet Ukraine ( including Lwów , Tarnopol , Lutsk , Rowne and Stanisławów ) . The city of Vilnius ( Polish : " Wilno " ) with its adjacent area was annexed and returned to Lithuania . After the German attack on the Soviet Union in June 1941 , the district of Białystok , which included the Białystok , Bielsk Podlaski , Grajewo , Łomża , Sokółka , Volkovysk , and Grodno Counties , was " attached to " ( not incorporated into ) East Prussia . The former Lwow , Stanislawow and Tarnopol Voivoideships were annexed to the General Government , forming its fifth district , Distrikt Galizien . 1945 . On Victory in Europe Day ( V - E Day : May 8 , 1945 ) World War II Allies formally accepted the unconditional surrender of Nazi Germany . After World War II , there were extensive changes to the territorial extent of Poland , following the decision taken at the Teheran Conference of 1943 at the insistence of the Soviet Union . The Polish territories east of the Curzon Line , which the Soviet Union had occupied in 1939 along with the Bialystok region , were permanently annexed . While a large portion of this area was predominately populated by Ukrainians and Belarussians , most of their Polish inhabitants were expelled . Today these territories are part of Belarus , Ukraine and Lithuania . Poland received former German territory east of the Oder - Neisse line , consisting of the southern two thirds of East Prussia and most of Pomerania , Neumark ( East Brandenburg ) , and Silesia . The German population was expelled before these formerly occupied territories were repopulated mainly with Poles from central Poland and those expelled from the eastern regions . Early expulsions in Poland were undertaken by the occupying Soviet and Polish Communist military authorities even before the Potsdam Conference ( " wild expulsions " ) . Poland USSR . On August 16 , 1945 , a border agreement between Poland and the USSR was signed . The western portion of the Byelorussian SSR was granted to Poland . The Belastok Voblast was divided into Soviet Brest Voblast , Hrodna Voblast and Polish Białystok Voivodeship . As a result , Poland lost about 178 , 000 sq km of its pre - war territory in the east , but gained some 101 , 000 sq km in the west and north . Czechoslovakia . After World War II the Czechoslovakian government wanted to return to the 1920 border between the two nations , while Polish inhabitants of Zaolzie were in favour of the boundary of August 31 , 1939 . On May 20 , 1945 , in Trstena an agreement for a return to the 1938 borders of Poland was signed and the following day the Czechoslovak border guards moved to the old Czechoslovakian border . At several places there were fights between Polish and Czechoslovakian militias , but the situation calmed with the arrival of Polish troops on July 17 , 1945 . The Polish government still did not want to give up Zaolzie , and on June 16 , 1945 , Marshall Michał Rola - Żymierski issued directive number 00336 , which ordered the 1st Armoured Corps of the Polish Army to concentrate in the area of Rybnik , and to seize Zaolzie . However , the Soviets decided to hand the region to Czechoslovakia , and the Poles followed the Moscow directive . The Czechs demanded former German areas of Klodzko , Glubczyce , and Racibórz , but after Soviet mediation , all sides signed a treaty on September 21 , 1945 , which accepted the December 31 , 1937 , Polish - Czechoslovak and Czechoslovak - German borderline as the boundary between the two countries . 1948 . The Polish border underwent a minor correction in 1948 , when the village of Medyka near Przemyśl was transferred to Poland . 1951 . On February 15 , 1951 Aleksander Zawadzki , the president of the Polish Republic , and Andrey Vyshinsky , the Presidium of the Supreme Soviet of the Union of Soviet Socialist Republics , signed " Treaty No . 6222 . Agreement between the Polish republic and the Union of Soviet Socialist Republics concerning the exchange of sectors of their state territories " . The treaty was a border adjustment , with Poland and the Soviet Union exchanging . 1955 . In 1955 a small area of land on Usedom Island ( Polish : Uznam ) was ceded from the GDR ( Eastern Germany ) to Poland . The water pump station of Swinemünde lies on that land and was therefore handed over to Poland . 1958 . On June 13 , 1958 , the " Agreement concerning the final demarcation of the state frontier " between Czechoslovakia and Poland was signed in Warsaw . Adam Rapacki signed for Poland and Václav David signed for Czechoslovakia . The treaty confirmed the border at the line of January 1 , 1938 , the situation before the Nazi - imposed Munich Agreement transferred territory from Czechoslovakia to Poland . 1975 . In March 1975 Czechoslovakia and Poland modified their border along the Dunajec to permit Poland to construct a dam in the Czorsztyn region , southeast of Kraków . 2002 . In 2002 , Poland and Slovakia made some further minor border adjustments :