This book was originally conceived to provide a comprehensive survey of the numerous underground nuclear Monitoring Posts in and around South Yorkshire during the period known as the "Cold War" (1946 to 1991). These sites were operated by the voluntary body of men and women of the Royal Observer Corps; whose origins date prior to World War 2 (WW2), and who occupied these Posts to provide a secretive warning and monitoring role in the event of a nuclear attack on the United Kingdom during the "Cold War". As the initial research to this book progressed; other protected sites were identified and were considered to be just as significant to the "Cold War" period and ultimately required inclusion.