With 75,000 casualties and 550,000 tonnes of bombs dropped, France was, after Germany, the country, on the Western Front the Allies bombed the most heavily between 1940 and 1945. The bombing was particularly intense at the time of the 1944 landings. In order to protect the population as far as possible from the bombing, passive defence included such protective measures as the imposition of a curfew.
In other measures inhabitants were furnished with navy blue material to black out windows if homes had no shutters and in the trains, light bulbs were painted blue. All this was to make it difficult for Allied bombers to find their targets easily once night had fallen. The curfew was also used to limit clandestine activity linked, in particular to Resistance activities such as sabotage and parachute landings which often took place at night. Nobody was allowed out at night without a pass and risked arrest if caught. Sirens alerted the population to the approach of squadrons of bombers, and these gave time for the civilian population to find refuge in underground shelters such as cellars.
In the United Kingdom many civilians built their own air-craft shelters in their gardens for example, made from steel panels. Public shelters were constructed of brick and cement but they were not very solid. During the Blitz, a German massive bombing campaign over England, from September 1940 to May 1941, 150,000 thousand people slept every night in London Underground stations.