From the start of the war, a British blockade on shipments to Germany affected its economy. Germany was particularly dependent on foreign supplies of oil, coal, and grain. Thanks to trade embargoes and the blockade, imports into Germany declined by 80 per cent. To safeguard Swedish iron ore shipments to Germany, Hitler ordered the invasion of Denmark and Norway, which began on 9 April. Denmark fell after less than a day, while most of Norway followed by the end of the month. By early June, Germany occupied all of Norway.
The Nazi regime promoted a liberal code of conduct regarding sexual matters and was sympathetic to women who bore children out of wedlock. Promiscuity increased as the war progressed, with unmarried soldiers often intimately involved with several women simultaneously. Soldier's wives were frequently involved in extramarital relationships. Sex was sometimes used as a commodity to obtain better work from a foreign labourer. Pamphlets enjoined German women to avoid sexual relations with foreign workers as a danger to their blood.
Use of the word "concentration" came from the idea of confining people in one place because they belong to a group that is considered undesirable in some way. The term itself originated in 1897 when the "reconcentration camps" were set up in Cuba by General Valeriano Weyler. In the past, the U.S. government had used concentration camps against Native Americans and the British had also used them during the Second Boer War. Between 1904 and 1908, the Schutztruppe of the Imperial German Army operated concentration camps in German South-West Africa (now Namibia) as part of its genocide of the Herero and Namaqua peoples. The Shark Island Concentration Camp in Lüderitz was the largest camp and the one with the harshest conditions.