If patriotism, as the blowhard Samuel Johnson once said, “is the last refuge of the scoundrel,” then “the national interest” must be the first. It is the most protean of justifications: by invoking it, states can just as easily legitimize military interventions as excuse unpardonable passivity. Who hasn’t at some point heard a government official voice their sympathy with the plight of such-and-such people, only to add that it isn’t in the US national interest to do anything about it? Ubiquitous in imperialist rhetoric, the phrase “national interest” is thus no less common in speeches by louche isolationists — it means, in other words, whatever the government wants it to mean.

Tracing the United States’ rise to regional hegemony, Sean Mirski’s We May Dominate the World is a compendium of how Washington, by equating the Monroe Doctrine with the national interest, sanctified scores of military interventions in its hemisphere. The United States’ foreign policy, Mirski says, “was consistently shaped by one central, overarching challenge” — the so-called problem of order. To ensure the integrity of the Monroe Doctrine, US policymakers felt compelled to intervene “whenever one of their neighbors met three conditions: it was strategically important, it was threatened by foreign powers, and it was too unstable or otherwise weak to defend itself.” By proclaiming the entire continent strategically important, the United States prepared the way for interventions wherever European empires might land their forces.

Mirski sketches three phases of American interventionism before World War II. From 1860 to 1896, the United States responded to European incursions by seeking to strengthen neighboring countries through commerce. Prosperous neighbors, Washington hoped, could themselves guarantee their own sovereignty, though the United States was of course prepared to use force if necessary. The second — most expansionist — phase began with the Spanish-American War and lasted until the end of World War I, when US regional hegemony had been secured. The third phase saw the return of the “Good Neighbor” policy; however, that brief imperialist hiatus famously came to a close with the Cold War. That, put very simply, is the evolution of American interventionism — but what of its consequences? Theoretically, interventions were supposed to stabilize restless countries, but in practice they resulted in ever more strife: