East Prussian plebiscite

The East Prussia(n) plebiscite (German: Abstimmung in Ostpreußen), also known as the Allenstein and Marienwerder plebiscite or Warmia, Masuria and Powiśle plebiscite (Polish: Plebiscyt na Warmii, Mazurach i Powiślu), was a plebiscite for self-determination of the regions southern Warmia (Ermland), Masuria (Mazury, Masuren) and Powiśle, which had been in parts of the East Prussian Government Region of Allenstein and of West Prussian Government Region of Marienwerder, in accordance with Articles 94 to 97 of the Treaty of Versailles.

Prepared during early 1920, it took place on 11 July 1920. The plebiscite was conducted by German authorities. According to Richard K. Debo, both German and Polish governments believed that the outcome of the plebiscite was decided by the ongoing Polish-Bolshevik War which threatened the existence of the newly formed Polish state itself and, as a result, even many German citizens of Polish ethnicity of the region voted for Germany out of fear that if the area was allocated to Poland it would soon fall under Soviet rule.

According to several Polish sources the German side engaged in mass persecution of Polish activists, their Masurian supporters, going as far as engaging in regular hunts and murder against them to influence the vote. Additionally the organisation of the plebiscite was influenced by Great Britain, which at the time supported Germany, fearing the increased power of France in post-war Europe.

According to Jerzy Minakowski due to terror and unequal status of German and Polish side, Poles boycotted the preparations for the plebiscite which allowed Germans to engage in falsifications. The German conducted plebiscite reported that majority of voters selected East Prussia over Poland (over 97% in the Allenstein Plebiscite Area () and 92% in the Marienwerder Plebiscite Area ()); most of the territories in question remained in the Free State of Prussia, and therefore, in Germany.

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