He studies international relations, with a focus on international security. He is the author of two books, The Economics of War (McGraw Hill-Irwin, 2006), which was translated into French, Japanese, and Chinese, and Organizing Democracy (University of Chicago Press, forthcoming), which will be published as part of the Chicago Series on International and Domestic Institutions. He has authored or co-authored academic papers in journals such as International Organization, World Politics, Political Analysis, the American Journal of Political Science, and the Journal of Conflict Resolution. His research has been funded by the National Science Foundation and featured in various news outlets, including The New York Times, Bloomberg, and Washington Post.