This book provides important recommendations for how the Department of Defense can better face the rapidly changing security environment of the 21st century by increasing its adaptability. The study used business and government case studies to derive its definition of adaptability which identified the key elements as the ability and willingness to anticipate the need for change, to prepare for that change, and to implement changes in a timely and effective manner in response to the surrounding environment. Strategies were identified to promote the elements of adaptability in the Department of Defense (DoD), with an ultimate goal of improving mission effectiveness, including aligning enterprise functions to support mission outcomes; reduce uncertainty through better global awareness; prepare for degraded operations; enhance the adaptability of the workforce and changing the culture.