to learn the opinions of the nationalist, economic, and military elites of the German ruling class who financed and facilitated geopolitics. Nationally, the annexation and ethnic cleansing of Poland for German was an official and a popular subject of "nationalism-as-national-security" endorsed by German society, including the Social Democratic Party of Germany (SDP). In The Origins of the Second World War, the British historian A. J. P. Taylor wrote: Interwar propaganda In the national politics of the Weimar Republic (1919–33), the German eugenicists took up the nationalist political slogan of , and matched it with the racial slogan (a People without Youth), a cultural proposition that ignored the declining German birth rate (since the 1880s) and contradicted the popular belief that the "German race" was a vigorous and growing people. Despite each slogan (political and racial) being contradicted by the reality of such demographic facts, the nationalists' demands for proved to be ideologically valid politics in Weimar Germany. In the lead-up to (1938) and the invasion of Poland (1939), the propaganda of the Nazi Party in Germany used popular feelings of wounded national identity aroused in the aftermath of the First World War to promote policies of . Studies of the homeland focused on the lost colonies after the establishment of the Second Polish Republic, which was ratified by the Treaty of Versailles (), as well as the "eternal Jewish threat" (, 1937). Emphasis was put on the need for rearmament and the pseudoscience of superior races in the pursuit of "blood and soil" (). During the twenty-one-year inter-war period between the First (1914–18) and the Second (1939–45) World War, for Germany was the principal tenet of the extremist nationalism that characterised German party politics. The Nazis, led by Adolf Hitler, demanded not only the geographic reversion of Germany's post-war borders (to recuperate territory lost by the Treaty of Versailles), but also the German conquest and colonisation of Eastern Europe (whether or not those lands were German before 1918). To that end, Hitler said that flouting the Treaty of Versailles was required for Germany to obtain needed in Eastern Europe. During the 1920s, Heinrich Himmler—as a member of the Artaman League, an anti-Slav, anti-urban, and anti-Semitic organisation of "blood and soil" ideology—developed the ideas that advocated , for the realisation of which he said that the: as theory in Hitlerism In (1925), Hitler dedicated a full chapter—titled "Eastern Orientation or Eastern