This book asserts that an interrelationship exists between U.S. military power, economic strength, its international standing, and the development and use of diplomacy. Given the United States' currently vacillating hegemony and stringent fiscal circumstances, this book further posits that U.S. diplomacy must adapt as it enters a new post-conflict period. This work presents and assesses three historical moments that illustrate the interplay developed over the last 120 years. It then forecasts a change in that relationship and recommends ways for diplomacy to evolve in order to continue achieving U.S. national security goals.