by the Swiss to becoming prisoners of war. Over a hundred Allied aircraft and their crews were interned in this manner. They were subsequently put up in various ski resorts that had been emptied from lack of tourists due to the war and held until hostilities ended. At least 940 American airmen attempted to escape into France after the Allied invasion of Normandy in June 1944 but Swiss authorities intercepted 183 internees. Over 160 of these airmen were incarcerated in a Swiss prison camp known as Wauwilermoos, which was located near Lucerne and commanded by André Béguin, a pro-Nazi Swiss officer. The American internees remained in Wauwilermoos until November 1944 when the U.S. State Department lodged protests against the Swiss government and eventually secured their release. The American military attaché in Bern warned Marcel Pilet-Golaz, Swiss foreign minister in 1944, that "the mistreatment inflicted on US aviators could lead to 'navigation errors' during bombing raids over Germany". Switzerland, surrounded by Axis-controlled territory, also suffered from Allied bombings during the war; most notably from the accidental bombing of Schaffhausen by American aircraft on 1 April 1944. It was mistaken for Ludwigshafen am Rhein, a German town away; forty people were killed and over fifty buildings destroyed, among them a group of small factories producing anti-aircraft shells, ball-bearings, and Bf 109 parts for Germany. The bombing limited much of the leniency the Swiss had shown toward Allied airspace violations. Eventually, the problem became so bad that they declared a zero-tolerance policy for violation by either Axis or Allied aircraft and authorized attacks on American aircraft. Victims of these mistaken bombings were not limited to Swiss civilians but included the often confused American aircrews, shot down by the Swiss fighters as well as several Swiss fighters shot down by American airmen. In February 1945, 18 civilians were killed by Allied bombs dropped over Stein am Rhein, Vals, and Rafz. Arguably the most notorious incident came on 4 March 1945, when Basel and Zurich were accidentally bombed by American aircraft. The attack on Basel's railway station led to the destruction of a passenger train, but no casualties were reported; a B-24 Liberator dropped its bomb load over Zürich, destroying two buildings and killing five civilians. The crew believed that they were attacking Freiburg in Germany. As John Helmreich points out, the pilot and navigator, in choosing a target of opportunity, "missed the marshalling yard