Thesis advisor: Robert Ross / Military balance of power and geographical proximity are two key factors that shape thelikelihood of war and peace in the realist paradigm. However, the empirical cases associated with the leading sea power and a naval challenger sometimes are not congruent to systemic anticipations of both the balance of power theory and hegemonic shift theories. Why do the leading sea power and a challenger fight a war despite naval power disparity and geographical distance? Conversely, how do these powers arrive at a strategic settlement even with naval power parity and geographical proximity? More practically, under what conditions are the U.S. and China more likely to avoid or end up in a war as China’s naval overtake looms large in the Asia-Pacific? To address these questions, I construct a mid-range theory, An Interactive Theory of Power Projection, that incorporates the geographical dimension of power projection in determining the outcome of naval power shifts. Specifically, I conduct comparative historical case studies of the two Anglo-French dyads (1856-1870/1882-1904) and the U.S.-Japan dyad (1921-1941) with a goal of developing a theory to apply to U.S.-China relations. At root, I argue that the outcome of a naval power transition is contingent upon two conditions: (1) the interactive dynamics of a challenger’s expansion and the leading sea power’s expectation about its contagion effect on the first line of maritime defense; and (2) whether alignment opportunity, shaped by third common threats and available allies in the theaters of the power transition, is open or closed. The contagion effect refers to three kinds of possibilities in the event of a challenger’s occupation: (1) an occupation will become a stepping stone on which a challenger further expands into the adjacent first line of maritime defense; (2) an occupation will produce a negative second-order effect on the other, possibly distant, first line of maritime defense; (3) an occupation will undermine or remove local allies on the first line of maritime defense. I argue that while bilateral resource-extraction capacities initiate or end a naval arms race, it is the interactive dynamics of geographical power projection as well as alignment opportunity in the theater of the naval challenge that bring a conflict to the fore and determine its outcome. These findings carry policy implications for U.S.-China relations and U.S. foreign policy. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Political Science.