This essay, a chapter in the international relations textbook Understanding War and Peace (see the textbook webpage), is one of the first essays ever published that explains the economics of war to undergraduates. It focuses on how governments pay for their armies, in war and peace. It begins with the canonical guns vs. butter tradeoff. The chapter then moves through a number of choices governments face when deciding how to mobilize for war, including: taxation or borrowing; using private military contractors or citizen-soldiers; building conscript or volunteer militaries; producing weapons domestically or purchasing them from foreign sources. The chapter also explains how economic factors like trade interdependence can bolster peace. The chapter includes a case study on taxation in the US during the World Wars, and a summary of a quantitative study exploring whether availability of international credit helps a state win a war.Most appropriate for classes on war and politics, and political economy.What makes this chapter different:●First ever undergraduate-appropriate essay on the economics of war●Comprehensive coverage of relevant topics accounts for contemporary scholarship●Approachable coverage, no economics background necessary.Dr. Paul Poast is assistant professor of political science at the University of Chicago. He is the author of several leading articles on economics and war, as well as The Economics of War (McGraw-Hill, 2006).