Lebensraum was a German term made popular by Adolf Hitler and the Nazis, which literally means "living room" or "living space". Lebensraum was a policy of expanding the territory of Germany, particularly to the east in what is modern Poland, Belarus, and Western Ukraine where many atrocities were committed and whole villages wiped out to create "living space" for urbanized Germans. Under Hitler's rule, lebensraum became the political rationale behind the Nazi conquest of territories lost by the German and Austro-Hungarian Empires by the Treaty of Versailles, which ended World War I.
Lebensraum has some roots in Malthusianism. Hitler wrote extensively about "living space" in his unpublished Zweites Buch (second book). In Hitler's Table Talk, minutes of Hitler's wartime dinner conversations, Hitler claimed Russia could be conquered up to the Urals, with a small contingent SS force as landowners guarding the new Reich beyond the Urals. Hitler also spoke of claiming the Crimea as a "German Riviera" resort.