The article reveals the assumptions under which Polish claims to Warmia and Masuria Regions were legitimated in the 20th c. and the impact made on the starting points of the policies applied after WWII to the integration of Warmia and Masuria into Poland by the ideological political situation and the ratio of powers formed in the years of the war. The author pays great attention to the disclosure of the policy of “de-Germanization” and its practices by demonstrating the ways of instrumentalization of anti-German attitudes by the postwar Polish authorities, thus promoting the symbolical integration of former German territories (the Recovered Lands) into the minds of Polish settlers in them.