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Just as the history of the world was written in Europe during the 19th and 20th centuries, the history of the 21st century will surely be written in the Asia-Pacific. Four decades of almost uninterrupted economic growth and the expansion of democratic governance has created a region of peace, prosperity, and integration that rivals almost any in history. The United States has been one of the greatest benefactors of Asia's success – we have gained access to new markets, formed deeper alliances to ensure stability, and seen the winds of democratic change sweep away ruthless autocrats.

But unnoticed by many is the fact that US military power and its alliances have underwritten the region's security for the last seven decades, creating a stable environment that continues to enable...