in Berlin for longer than two days and were housed in camps near the city before being moved on westwards; it is estimated less than 50,000 managed to remain in Berlin. By January 1945 the population was around 2.9 million, although the demands of the German military were such that only 100,000 of these were males aged 18–30. Another 100,000 or so were forced labor, mainly French Fremdarbeiter, "foreign workers", and Russian Ostarbeiter ("eastern workers"). The key to the Flak area were three huge Flak towers (Flaktürme), which provided enormously tough platforms for both searchlights and 128 mm anti-aircraft guns as well as shelters (Hochbunker) for civilians. These towers were at the Berlin Zoo in the Tiergarten, Humboldthain and Friedrichshain. The Flak guns were increasingly manned by the teenagers of the Hitler Youth as older men were drafted to the front. By 1945 the girls of the League of German Girls (BDM) were also operating Flak guns. After 1944 there was little fighter protection from the Luftwaffe, and the Flak defences were increasingly overwhelmed by the scale of the attacks. Timeline Notes References Quester, George H. (1986). Deterrence before Hiroshima: the airpower background of modern strategy'', Transaction Publishers; Strategic operations of the Red Army in World War II Berlin Berlin Firebombings 1940s in Berlin Articles containing video clips