As a result of a commission of Edwin Oostmeijer Development to investigate the background of a German shelter near the Servaasbulwark at Utrecht, Bosma carried out an international research of the air raid protection of citizens in the period since 1933 in England, Germany and the Netherlands. The research led to the book Schuilstad. Bescherming van de bevolking tegen Luchtaanvallen (SUN, 2006). In the book the measures that were taken in Europe and above all in the Netherlands to protect citizens against air raids on the eve of World War II, during the occupation, in the Cold War and after are dealt with. The foundations of present day emergency planning and spreading of risks mainly descend from the thirties and forties. In recent times they are, aside from technical innovations, relatively new threads (like international terrorism and different military strategies), changed substantially.
Ideas about air raid protection, the developing of emergency plans, the education of air raid staff and even ideas to build complete parallel cities to shelter citizens – the efficiency of all these efforts are tested at the supreme moment: how much security offers the air raid protection shield when the thread switches over to an actual air attack? But, although cities and their inhabitants are vulnerable to technically advanced attacks, they always prove to be tough and do not let themselves wipe off the map.