The Generalplan Ost (GPO) () was a secret Nazi German plan for the colonization of Central and Eastern Europe. Implementing it would have necessitated genocide and ethnic cleansing on a vast scale to be undertaken in these European territories, occupied by Germany during World War II. It would have included the enslavement, expulsion and extermination of most Slavic peoples in Europe. The plan, prepared in the years 1939–1942, was part of Adolf Hitler's and the Nazi movement's Lebensraum policy and a fulfillment of the Drang nach Osten () ideology of German expansion to the east, both of them part of the larger plan to establish the New Order.