not live under the dominion of a race which they had previously oppressed and despised." Germans feared that the Poles would seek reprisals after over a century of harassment and discrimination by the Prussian and German state against the Polish population. Social and linguistic isolation: While the population was mixed, only Poles were required to be bilingual. The Germans usually did not learn Polish. When Polish became the only official language in Polish-majority provinces, their situation became difficult. The Poles shunned Germans, which contributed to their isolation. Lower standards of living. Poland was a much poorer country than Germany. Former Nazi politician and later opponent Hermann Rauschning wrote that 10% of Germans were unwilling to remain in Poland regardless of their treatment, and another 10% were workers from other parts of the German Empire with no roots in the region. Blanke says that official encouragement by the Polish state played a secondary role in the German exodus. Christian Raitz von Frentz notes "that many of the repressive measures were taken by local and regional Polish authorities in defiance of Acts of Parliament and government decrees, which more often than not conformed with the minorities treaty, the Geneva Convention and their interpretation by the League council - though it is also true that some of the central authorities tacitly tolerated local initiatives against the German population." While there were demonstrations and protests and occasional violence against Germans, they were at a local level, and officials were quick to point out that they were a backlash against former discrimination against Poles. There were other demonstrations when Germans showed disloyalty during the Polish–Soviet War as the Red Army announced the return to the pre-war borders of 1914. Despite popular pressure and occasional local actions, perhaps as many as 80% of Germans emigrated more or less voluntarily. Helmut Lippelt writes that Germany used the existence of German minority in Poland for political ends and as part of its revisionist demands, which resulted in Polish countermeasures. Polish Prime Minister Władysław Sikorski stated in 1923 that the de-Germanization of these territories had to be ended by vigorous and quick liquidation of property and eviction of German "Optanten" (Germans who refused to accept Polish citizenship and per the Versailles Treaty were to leave Poland) so that German nationalists would realise that their view of the temporary state of Polish western border was wrong. To Lippelt this was