International trade in strategic materials was critical to Allied victory in the Second World War, yet little is known about how that trade functioned in practice. This paper studies wartime imports of Chilean nitrate, which enabled the United States to increase food production without sacrificing munitions output. The US imported nitrate and other resources through a public purchase program that depended on the coordination and cooperation of a vast bureaucracy. Government agencies weighed the benefits and costs of Chilean nitrate differently and intervened at key junctures. For their part, Chilean corporate and diplomatic staff worked meeting rooms in Washington, negotiating the purchase contracts and managing day-to-day business with the US government. Chilean actors meanwhile pursued their own interests while contributing to the Allied victory. The business history of the US–Chilean nitrate trade demonstrates how Chile, sometimes mischaracterized as a disinterested neutral on the fringes of the conflict, played an important role during the Second World War.