Since at least Cicero, we have known that “money is the sinew of war.” Is it possible for a political economy of security (PES) subfield to contribute knowledge beyond Cicero's claim? This article aims to delineate the boundaries of a PES subfield by using the classic “guns versus butter” trade-off to define the existing literature within the subfield. Thinking seriously about this trade-off, including conditions under which a trade-off may not exist, raises a host of questions. The two most direct questions are: How does consuming “guns” influence the consumption of “butter”? And how does using “guns” influence the consumption of “butter”?