From 1943 Switzerland stopped American and British aircraft, mainly bombers, overflying Switzerland during the Second World War. On numerous occasions during the war, Allied aircraft trespassed on Swiss airspace; mostly damaged Allied bombers returning from raids over Italy and Germany whose crews preferred internment by the Swiss to becoming prisoners of war. Over a hundred Allied aircraft crews were interned and placed in ski resorts which were left abandoned due to the lack of tourists after the outbreak of war. They were to be held in there until the war had ended.[20] At least 940 American airmen attempted to escape into France after the invasion of Normandy, 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.