The US-Japan alliance: historical foundations, strategic interests, and geopolitical challenges in the 21st century

This thesis analyzes the evolution of the U.S.–Japan alliance from its postwar foundations to the complex strategic environment of the twenty-first century. It examines how historical asymmetries, shifting strategic interests, and geopolitical pressures have shaped the alliance’s transformation. Through a combination of historical analysis, policy review, and case-based evaluation of regional security challenges, the study explores three core dynamics: the expansion of economic and technological cooperation, the deepening of defense integration, and the management of China, Taiwan, and North Korea as central security concerns. The findings demonstrate that the alliance has moved beyond a traditional defense framework toward a multidimensional partnership grounded in economic security, advanced technology, and emerging domains such as cyberspace and space. Despite persistent asymmetry, Japan’s reliance on U.S. extended deterrence and the U.S. reliance on Japan’s geography and technological capabilities, the relationship has evolved into a form of strategic interdependence. Geopolitical developments, particularly China’s rise and the increasing salience of a Taiwan contingency, further accelerate this trend. The thesis argues that the alliance will continue to strengthen as regional competition intensifies, but its long-term sustainability will depend on domestic political support, fiscal capacity, and the ability of both states to manage structural imbalances. Ultimately, the U.S.–Japan alliance has become a central pillar of Indo-Pacific security and a key instrument for shaping regional order amid growing geopolitical uncertainty.