resulting fighting brought total US losses to approximately 68,000. In addition, the First Army incurred over 50,000 non-battle casualties and the Ninth Army over 20,000. This brings the overall cost of the Siegfried Line Campaign, in US personnel, close to 140,000. Postwar period During the postwar period, many sections of the Siegfried Line were removed using explosives. Preservation and destruction In North Rhine Westphalia, about thirty bunkers still remain; most of the rest were either destroyed with explosives or covered with earth. Tank traps still exist in many areas; in the Eifel, they run over several kilometres. Zweibrücken Air Base was built on top of the Siegfried Line. When the base was still open, the remnants of several old bunkers could be seen in the tree line near the base's main gate. Another bunker was outside the base perimeter fence near the base hospital. Once the base was closed, workers, digging up the base's fuel tanks, discovered lost bunkers buried below the tanks. Since 1997, with the motto "The value of the unpleasant as a memorial" (Der Denkmalswert des Unerfreulichen), an effort has been made to preserve the remains of the Siegfried Line as a historical monument. This was intended to stop reactionary fascist groups from using the Siegfried Line for propaganda purposes. At the same time, state funding was still being provided to destroy the remains of the Siegfried Line. For this reason, emergency archaeological digs took place whenever any part of the line was removed, for example for road building. Archaeological activity was not able to stop the destruction of these sections but furthered scientific knowledge and revealed details of the line's construction. Environmental conservation Nature conservationists consider the remains of the Siegfried Line valuable as a chain of biotopes where, thanks to its size, rare animals and plants can take refuge and reproduce. This effect is magnified because the concrete ruins cannot be used for agricultural or forestry purposes. Westwall construction programmes Border Watch Small bunkers with thick walls were set up with three embrasures towards the front. Sleeping accommodations were hammocks. In exposed positions, similar small bunkers were erected with small round armoured "lookout" sections on the roofs. The programme was carried out by the Border Watch (Grenzwacht), a small military troop activated in the Rhineland immediately after the region was re-militarised by Germany after having been de-militarised following the First World War. Limes The Limes