This monograph addresses the perplexing issue of ensuring US security strategy is coherently mated with emerging defense doctrines. America's current security strategy, "engagement," is inherently dynamic in nature. Consequently, it has surfaced four defense related issues: mission profiles beyond the design of US armed forces, debate over the role of US armed forces within an "engagement" construct, debate over the future nature of US Security Policy and doctrinal changes by the Armed forces to meet the demands generated by "engagement." This monograph investigates the challenges facing the US Armed Services to develop relevant doctrine adaptable to dynamic changes in national security strategies. To meet the challenges of "Engagement" the services have adopted new doctrines affecting the way they organize, train, and equip: USAF, "Global Engagement;" USN, "Forward From the Sea;" and USA, "Army Vision 2010." Simultaneously, "engagement" itself has been debated with three schools of thought emerging: the "dynamic," "selective," and "disengagement" schools. Consequently, a programmatic dilemma is emerging; while the services are actively develop new doctrines to satisfy national security needs, the more cardinal issue of long-term national security policy is unsettled. The monograph assesses the emerging service doctrines ability to meet the demands of possible future national security strategies by contrasting focus of each emerging service doctrine against the argument of each security strategy "school." It employs complexity theory, the historic dynamics of "great nation" foreign policy development, historic and contemporary view of US security policy and theories of international security to develop perspectives on the nature of security policy. It surveys components of US power and review the National Security Strategy (NSS) to evaluate the ability of the armed forces to support the NSS. Finally, it investigates the US security strategy debate and contrasts the emerging service doctrines against the three schools of security doctrine. It then considers the plausibility of each school with consideration to complexity theory, historical perspectives and realistic military capabilities. The study concludes that future national security strategy will continue to emphasize security an economic prosperity founded on a stable international economic system. To ensure stability the US will remain internationally engaged in economic, diplomatic, and military dimensions. The Armed Services have developed coherent doctrines that while challenged by current demands, provide the flexibility to address the fundamental demands of either the "dynamic" or "selective" schools of engagement.