Versailles Plebiscite
The Treaty of Versailles had ordered a plebiscite in Upper Silesia to determine whether the territory should be a part of Germany or Poland. The plebiscite was to be held within two years of the Treaty (signed in 1919) in the whole of Silesia, although the Polish government only wanted it to be held in the part of Silesia east of the Oder river where there were significant numbers of Polish speakers. It was however decided to hold the plebiscite in all of Upper Silesia, including both the predominantly Polish-speaking areas in the east and the predominantly German-speaking Upper Silesian areas west of the river.
It was decided by the Allies that the Upper Silesian plebiscite was to be conducted on March 20, 1921. In the meantime, German administration and police were left in place.
In the background, propaganda and strongarm tactics on both sides led to increasing unrest. The German authorities warned that those voting for Poland would lose their jobs and pensions. Former German Army veterans joined "Freikorps" (Free Corps), an organization whose troops terrorized pro-Polish activists. At the same time, Poles argued that under the new Polish regime, Silesian Poles would no longer be discriminated against; the Poles also promised to honor the German state social benefits such as the old age pensions. The Polish sides also employed the Polish Military Organisation - a secret military organization and predecessor of Polish intelligence - to further their cause.
Eventually the deteriorating situation resulted in the first two Silesian Uprisings in 1919 and 1920.
The plebiscite took place as arranged on March 20, two days after the signing of the Treaty of Riga, on March 18, 1921, which ended the Polish-Soviet war of 1919–1920.
In the plebiscite, around 707,605 votes were cast for Germany, while 479,359 for Poland. The Germans thus had 228,246 votes of majority.
A right to vote was granted to those aged 20 and older who had been born in or lived within the plebiscite area. A result was mass migration. The German outvoters numbering 179,910; the Polish numbering over 10,000. Without the outvoters, the Germans would have a majority of 58,336 instead of 228,246. However, the inclusion of outvoters had been done by explicit request of the Polish delegation in Versailles who counted on the support of pro-Polish organizations in the Ruhr area.
The Third Silesian Uprising broke out in 1921. The League of Nations was asked to settle the matter before it led to even more bloodshed. In 1922, a six-week investigation determined that the land should be divided between the two nations. This decision was accepted by both countries, and the majority of Upper Silesians (whereby the Germans having lost World War I had no power to oppose such a decision). Approximately 736,000 Poles and 260,000 Germans lived in Polish (Upper) Silesia and 532,000 Poles and 637,000 Germans in German (Upper) Silesia.
Read more about this topic: Silesian Uprisings