The costs and consequences of the United States’s twenty-first-century wars have by now been well-documented — a staggering $8 trillion in expenditures and more than 380,000 civilian deaths, as calculated by Brown University’s Costs of War project. The question of who has benefited most from such an orgy of military spending has, unfortunately, received far less attention.

Corporations large and small have left the financial feast of that post-9/11 surge in military spending with genuinely staggering sums in hand. After all, Pentagon spending has totaled an almost unimaginable $14 trillion plus since the start...