Eastward settlement (Ostsiedlung) by Germans gathered momentum in medieval times, and was often through invitation of local rulers who valued the settlers’ industry, skills and martial prowess. The Teutonic Knights controlled East Prussia for centuries, promoting German settlement, while the commercial empire of the Hanseatic League dispersed German merchants throughout the Baltic.
Poland and Prussia
During the three Polish partitions from 1772–95 the Kingdom of Prussia acquired the territories of Polish Prussia and the province of Posen, amounting to 20 per cent of the former Commonwealth of Poland, which was effectively eliminated for the next 123 years. After the upheavals of the Napoleonic Wars and the short-lived Duchy of Warsaw (1807–15), the Prussian government was able to pursue a policy of Germanization throughout the first half of the 19th century, dominating administrative and judicial institutions and suppressing the use of the Polish language, spoken by the majority of the population
The Germanization of Poland
From 1886–1918, Bismarck’s Prussian Settlement Commission organized the planned transplantation of Germans to West Prussia. The Commission was a major instrument in the Germanization of these formerly Polish lands. By the end of its operation a total of 21,886 German families had been settled in the east and great efforts had been made to diminish Polish national identity – large estates were bought up by the Commission and distributed to German colonists, who were overwhelmingly Protestant, and who were given many economic inducements to settle in the east. Inevitably, German attempts to diminish Polish power and influence were met with Polish resistance and merely served to reinforce and foster feelings of Polish nationalism.
Germany’s eventual defeat in World War I and the territorial provisions made by the Treaty of Versailles were to have a dramatic impact on the region. Most of West Prussia and the province of Posen was ceded to the newly-formed Polish state, which was also given a thin strip of land around the River Vistula, which provided access to the Baltic, and vital economic rights to the free port city of Danzig. The primarily German-speaking city Danzig was effectively separate from both Germany and Poland, under the protection of the League of Nations, but in a customs union with Poland, which had the rights to maintain transportation, communication and port facilities within the city. This resulted in German East Prussia becoming an exclave and meant that large numbers of German-speaking peoples in the newly formed corridor fell under Polish rule.
Many Germans were forcibly evicted from the Danzig corridor post-1919, or chose to leave voluntarily, unable to submit to government by a race that had formerly been despised and marginalized. Transport between East Prussia and Germany through the corridor also became very restricted – trains passing through the Corridor had sealed carriages (Korridorzug), so that transiting passengers did not have to possess Polish visas, but thorough searches by the Polish authorities were feared and resented. Successive Weimar governments refused to recognize the eastern borders agreed at Versailles. These issues provided the pretext for much of the tension that sparked World War II, as Hitler capitalized on resentment over Poland’s refusal to cede the territory back to Germany and called for the unification of all German peoples.