This manual provides guidance for the organization, planning, and conduct of the full range of military operations on urbanized terrain. This publication was prepared primarily for commanders, staffs, and subordinate leaders down to the squad and fire team level. It is written from a Marine air-ground task force perspective, with emphasis on the ground combat element as the most likely supported element in that environment. It provides the level of detailed information that supports the complexities of planning, preparing for, and executing small-unit combat operations on urbanized terrain. It also provides historical and environmental information that supports planning and training for combat in built-up areas

Doctrine provides a military organization with a common philosophy, a language, a purpose, and unity of effort. Rather than establishing a set of hard and fast rules, the objective of doctrine is to foster initiative and creative thinking. To this end, FM 3-06 discusses major Army operations in an urban environment. This environment, consisting of complex terrain, a concentrated population, and an infrastructure of systems, is an operational environment in which Army forces will operate. In the future, it may be the predominant operational environment. Each urban operation is unique and will differ because of the multitude of combinations presented by the threat, the urban area itself, the major operation of which it may be part (or the focus), and the fluidity of societal and geopolitical considerations. Therefore, there will always exist an innate tension between Army doctrine, the actual context of the urban operation, and future realities. Commanders must strike the proper balance between maintaining the capability to respond to current threats and preparing for future challenges.

From the Foreword: "The story of the Marine Corps U.S. Special Operations Command Detachment, which became known as Det One, is an extraordinary tale. On its face, the story would not rate a minute's glance. One small group of Marines, about a hundred in number, formed, trained, and went to war. This all happened as the nation was 18 months into the Global War on Terrorism and as the Marine Corps was deploying I Marine Expeditionary Force in Operation Iraqi Freedom. Yet the story behind the basic facts is not only far more intricate and fascinating, with dramatic episodes and intrepid characters from the Pentagon to Camp Pendleton, it portended great significance for the Marine Corps. What makes the Det One story extraordinary is the shift in Marine Corps policy that brought it about, the maturation of the special operations capabilities of forward-deployed Marine expeditionary units that made it possible, and the patriotism, valor, fidelity, and abilities of the Marines and Navy Corpsmen who manned it. Although Det One has passed now into the history books, its legacy survives in the formation of Marine Corps Special Operations Command and in the lessons learned and experiences of its members, who now continue to serve in dozens of units. Lieutenant Colonel John P. Piedmont Marine Field Historian in Iraq in April 2004, saw the historical significance of Det One and decided to pursue its history as a project. Under the director of the History and Museums Division at the time, Colonel John W. Ripley, he was given permission to proceed with his collections with a view toward turning them into a monograph. What follows here is the culmination of his efforts, the product of two years' work, more than 60 interviews done in Iraq, Washington, D.C., Virginia, and California, and the collection of hundreds of documents."--Dr. Charles P. Neimeyer.