Andrzej Chwalba. By 1921 the proportion of Germans had dropped to 18.8% (175,771). Over the next decade, the German population decreased by another 70,000 to a share of 9.6%. German political scientist Stefan Wolff, Professor at the University of Birmingham, says that the actions of Polish state officials after the corridor's establishment followed "a course of assimilation and oppression". As a result, a large number of Germans left Poland after 1918: according to Wolff, 800,000 Germans had left Poland by 1923, according to Gotthold Rhode, 575,000 left the former province of Posen and the corridor after the war, according to Herrmann Rauschning, 800,000 Germans had left between 1918 and 1926, contemporary author Alfons Krysinski estimated 800,000 plus 100,000 from East Upper Silesia, the contemporary German statistics say 592,000 Germans had left by 1921, other Polish scholars say that up to a million Germans left. Polish author Władysław Kulski says that a number of them were civil servants with no roots in the province and around 378,000, and this is to a lesser degree is confirmed by some German sources such as Hermann Rauschning. Lewis Bernstein Namier raised the question as to whether many of the Germans who left were actually settlers without roots in the area - Namier remarked in 1933 "a question must be raised how many of those Germans had originally been planted artificially in that country by the Prussian Government." The above-mentioned Richard Blanke, in his book Orphans of Versailles, gives several reasons for the exodus of the German population: A number of former settlers from the Prussian Settlement Commission who settled in the area after 1886 in order to germanise it were in some cases given a month to leave, in other cases they were told to leave at once. Poland found itself under threat during the Polish-Bolshevik war of 1919-1921, and the German population feared that Bolshevik forces would control Poland. Migration to Germany was a way to avoid conscription and participation in the war. State-employed Germans such as judges, prosecutors, teachers and officials left as Poland did not renew their employment contracts. German industrial workers also left due to fear of lower-wage competition. Many Germans had become economically dependent on Prussian state aid as Prussia had fought the "Polish problem" in its provinces. Germans refused to accept living in a Polish state. As Lewis Bernstein Namier said: "Some Germans undoubtedly left because they would