Principles of Protection sets forth the definitive design standards for underground shelter engineering. This is the book the U.S. government should have written for the protection of its citizens. Walton McCarthy's research started in 1978 when he was privately funded for the educational research that formed the basis of his first book, The Nuclear Shelterist. He thereafter wrote Principles of Protection: The U.S. Handbook of NBC Weapon Fundamentals and Shelter Engineering Design Standards, known in the industry as POP. This book is now in its sixth edition for 2013. McCarthy has designed and built over 1,400 shelters using steel, concrete, wood, fiberglass, and plastic composites.