There was resistance among the Masurians towards Germanization efforts , the so-called Gromadki movement was formed which supported use of Polish language and came into conflict with German authorities ; while most of its members viewed themselves as loyal to the Prussian state , some of them joined the Pro-Polish faction of Masurians . In general , popular resistance against linguistic Germanisation can not be easily equated with anti-German sentiment or a strong attachment to the Polish national movement . Most of Masuria 's small Polish-speaking intelligentsia remained decisively pro-Prussian , often adhering to an older , multi-ethnic model of Prussian identity , centred on loyalty to their king , not so much on the German language . This ethnically , but not nationally Polish identity was a repeated source of consternation for Polish national activists , and decidedly pro-Polish political parties and press never gained widespread influence among the general populace . Richard Blanke summarised this long-standing attachment , going back to the late Middle Ages , as " Masurians became Prussian , in other words , before the Bretons ( not to mention the Alsatians ) became French . " The Masurians evinced strong support for Germany during World War I . In 1920 the League of Nations supervised the East Prussian plebiscite - with British , French and Italian troops stationed in Masuria - to determine the new border between the Second Polish Republic and German East Prussia . The plebiscite was organized by the local German authorities . Polish ethnographer Adam Chętnik stated that the German authorities performed abuses and falsifications during the plebiscite , and Stefan Berger writes that the Masurians were subjected to huge psychological pressure and physical violence by German side to vote for Germany . Kossert admits irregularities during the referendum , but asserts that in general , its results truthfully reflected the overwhelmingly pro-German sentiment in southern East Prussia . In Masuria proper the vast majority ( 99.32 % ) opted to remain in Prussia . Attempts to create schools teaching Polish in interwar Germany were met with terror and violence Support for the Nazi Party was high in Masuria , especially in elections in 1932 and 1933 . Nazis used the Masurian dialect for their political rallies during the campaigning . The government of Nazi Germany changed the names of several Masurian towns and villages from their original Slavic or Baltic Prussian names to new German names in 1938 . During World War II the Nazis persecuted and killed Polish speakers in Masuria and imprisoned Polish teachers as well as children who learned Polish . The Nazis believed that in future the Masurians as separate non-German entity , would disappear , while those who would cling to their " foreignness " as one Nazi report mentioned , would be deported . Poles and Jews were considered by Nazis to be " untermenschen " , subject to slavery and extermination , and Nazi authorities murdered Polish activists in Masuria , those who were n't killed were arrested and sent to concentration camps , In 1943 " Związek Mazurski " was reactivated secretly by Masurian activists of the Polish Underground State in Warsaw and led by Karol Małłek . Związek Mazurski opposed Nazi Germany and asked Polish authorities during the war to liquidate German property after victory over Nazi Germany to help in agricultural reform and settlement of Masurian population , Masurians opposed to Nazi Germany requested to remove German heritage sites " regardless of their cultural value " . Additionally a Masurian Institute was founded by Masurian activists in Radość near Warsaw in 1943 . Andreas Kossert regards these claims as a presumption completely disregarding the actual conditions of the Masurian people . Along with the majority of ethnic German East Prussians , many Masurians fled to western Germany as the Soviet Red Army approached East Prussia in 1945 in the final European campaigns of World War II . The post-war Potsdam Conference placed Masuria - and the rest of southern East Prussia - under Polish administration . Many Masurians who were classified as Germans were expelled with military force . After 1956 many who had remained in Poland emigrated to West Germany , approximately 5,000 Masurians still lived in the area , many of them as members of the German minority . Speculations about the reasons of this emigration vary from the economic situation and the undemocratic - communist - system in Poland to the shrinking prospect of a return of Masuria to Germany
Potsdam Conference
Potsdam Conference
Masurians