10. United States and Japan
From enemy combatants in World War II to strategic allies, the U.S.-Japan relationship has evolved into a cornerstone of Asia-Pacific security. The 1960 Treaty of Mutual Cooperation and Security established a framework for defense collaboration, while the 1997 Guidelines for U.S.-Japan Defense Cooperation expanded bilateral military coordination. In 2015, Japan reinterpreted its pacifist constitution, allowing for collective security measures. The alliance has been further strengthened through joint military exercises, intelligence sharing, and cooperation on regional security challenges, underscoring a shared commitment to peace and stability (cfr.org).
