Most of the demographic and cultural outcome of the was terminated after World War II . The expulsion of Germans after World War II east of the line in 1945 – 48 on the basis of decisions of the Potsdam Conference were later justified by their beneficiaries as a rollback of the . " Historical Eastern Germany " , which historically was the land of the Baltic people called Old Prussians who had been colonised and assimilated by German , was split between Poland , Russia , and Lithuania ( a Baltic country ) and repopulated with settlers of the respective ethnicities . The line has been accepted to be the eastern German boundary by all post-war German states ( East and West Germany , as well as reunited Germany ) , reneging on all plans to ( re - ) expand into or ( re - ) settle territories beyond this line . The Old Prussians were conquered by the Teutonic Knights in the 13th century , and gradually assimilated over the following centuries ; the Old Prussian language was extinct by the 17th or early 18th century . Henry Cord Meyer , in his book " : Fortunes of a Slogan-Concept in German – Slavic Relations , 1849 – 1990 " claims that the slogan originated in the Slavic world , and it also was more widely used than in Germany
Potsdam Conference
Potsdam Conference
Drang nach Osten