Preponderance in U.S. Foreign Policy: Monster in the Closet identifies and explains the factors contributing to the presence and severity of blunders, or gross errors in strategic judgment resulting in significant harm to the national interest, in U.S. foreign policy since 1945. It contends that when U.S. policymakers overestimate the capacity of American power to transform the politics of other states, the likelihood of a foreign policy resulting in a blunder increases. It concomitantly contends that the prevailing grand strategy of American preponderance since the Second World War precipitates the frequency and severity of foreign-policy blunders. The dissertation pursues four original lines of research: (1) the presentation of a sui generis framework for foreign-policy evaluation; (2) the new delineation of the concept and classification of the foreign-policy blunder; (3) the gathering of empirical data with regard to the decision-making of policymakers and the results of two corresponding foreign-policy blunders, the Vietnam War and the Iraq War; and (4) the demonstration of the two contentions within the overarching research question of what factors contribute to the presence and severity of blunders in modern U.S. foreign policy. The book presents a theoretical model examining and explaining the cultural and ideational connections between the pursuit of the grand strategy of American preponderance, decision-making in U.S. foreign policy, and blunders in modern U.S. foreign policy.