Estimating Alliance Costs: An Exchange

Abstract

In their ambitious article, Joshua Alley and Matthew Fuhrmann ask how “alliance commitments affect US military spending.” Their answer: each alliance, on average, adds $11–$22 billion to the annual defense budget. Given the number of US defense pacts, that would mean formal alliances accounted for over $735 billion of the 2019 defense budget. This finding, if true, suggests that Donald Trump was right to claim that alliances are “much too costly for the US.” In this reply, we show that supporters of contemporary US grand strategy can rest easy. Given the actual size of US defense budgets, Alley and Fuhrmann’s estimates cannot be correct. Even if their statistical models produced plausible numbers, the article remains deeply flawed. First, the article conflates its spending estimates with fixed costs. How much the United States spends, either directly or indirectly, on its formal alliances is almost entirely a matter of policy decisions and political processes; the United States can reduce the “average cost” of its formal alliances any time it wants to—by cutting the defense budget. Nothing about defense pacts forces Congress to appropriate funds for, say, another aircraft carrier or new generation of strike aircraft. For the same reason, we see no particular reason to think that if the United States shed an alliance (or ten) tomorrow then Congress would reduce military spending. Second, the key grand-strategy debate between “restrainers” and “engagers” concerns whether the United States should dramatically reduce its security commitments or military presence in some combination of Europe, the Middle East, and East Asia. Knowing the average “price tag” per defense pact does not help us decide which, if any, of those regions the