Isolationism, Turbulence, and Continuity: An Episode-Based Analysis of Interwar and Post-Cold War U.S. Administrations

The longstanding disputes over U.S. isolationism and global leadership have intensified amid Trump’s recent choices and the continuing U.S. response to both partners and rivals. Yet these debates often infer isolationism from rhetoric, institutional withdrawal, or a few prominent episodes rather than from a comparable long-run behavioral baseline. This article addresses that problem by applying a fully operationalized definition of isolationism – voluntary non-intervention and/or political disengagement where the United States could act, with only reluctant unilateral action under imminent threat to narrowly defined vital interests – together with an original isolationism index based on observed foreign-policy episode responses. Using the International Crisis Behavior dataset and archival sources, it generates comparable isolationism scores across U.S. administrations in the interwar and post-Cold War eras. The findings revise both accounts that interpret America First in isolationist terms and those that reject such readings, while also adding nuance to debates over inertia versus abrupt change in U.S. foreign policy. Interwar isolationism was generally lower, and post-Cold War isolationism higher, than commonly assumed. While interwar levels remain higher overall, this gap is driven almost entirely by Roosevelt’s first two terms. Other administrations from both eras fall into a similar range. Furthermore, many interwar non-responses concerned low-salience episodes, explaining this convergence once we account for episode relevance. In historical perspective, the results are more consistent with a recurring tension between attempted foreign-policy redirection and durable continuity than with exceptional rupture under any one presidency. Variation in isolationism recurs where presidential intent, advisory alignment, and external pressure diverge – a mismatch between stated direction and implemented behavior that the episode-level record makes visible. The article does not claim causality, but it provides a historical behavioral baseline for current debates on U.S. foreign-policy turmoil, inertia, and change.