This book, in Italian and English, collects the papers presented at the Second International Congress on Conoscenza e valorizzazione delle opere militari moderne - Knowledge and development of modern military structures, held at the Politecnico di Milano, Campus Bovisa, on 27 and 28 November 2012. The Congress was devoted to two types of military structures made between 1919 and 1939 in Italy and in some European countries: Theatres of war and Air-raid shelters in urban areas. Papers illustrate the structural characteristics and recent experiences of reuse and exploitation, even by cultural Association. It is an important contribution to the development and dissemination of studies on European defensive systems and on air defense of the city between 1919and 1939, a period still poorly understood with regard to the military architecture and the protection of civilians and cities by air raids. The book gathers updated data and documents in many cases unpublished.