The Correlates of War Project was founded in 1963 by J. David Singer, a political scientist at the University of Michigan. The original and continuing goal of the project has been the systematic accumulation of scientific knowledge about war. Joined by historian Melvin Small, the project began its work by assembling a more accurate data set on the incidence and extent of inter-state and extra-systemic war in the post-Napoleonic period. To do this scientifically Singer and Small found they needed to operationally resolve a number of difficult issues such as what is a “state” and what precisely is a “war.” Building upon the work of other pioneers such as Pitirim Sorokin, Lewis Frye Richardson, and Quincy Wright, Singer and Small published The Wages of War in 1972, a work that established a standard definition of war that has guided the research of hundreds of scholars since its publication.

This publication was only the beginning of the project, for the fundamental goal of the project was not just to measure the temporal and spatial variation in war but rather to identify factors that would systematically explain this variation. Accordingly, early efforts were undertaken to measure many of those factors that purportedly accounted for war such as national capability, alliances, geography, polarity, and status in the post-Napoleonic period, and the list of data sets assembled by the project has continued to grow over the years. In addition to the collection of data, the project has conducted many empirical studies about war and conflict. An important progeny of the project is the Behavioral Correlates of War project headed by Russell Leng. Through the years, the project has served as a major training ground for young scholars, and many of today’s best known and widely respected international relations scholars are “products” of the project. More generally, the correlates of war project promoted cumulative science in the field of international relations when the scientific study of politics was in its infancy. By helping to establish a clear temporal and spatial domain for research, promoting the use of clearly defined concepts and common variable operationalizations, and allowing replication of research, the project has been a mainstay of rigorous international relations scholarship.

In the late 1990s scholars became concerned about how the work of the project could be continued given the pending retirement of J. David Singer, and arrangements were made to transfer the project to Penn State under the leadership of Stuart A. Bremer. This transfer was marked by a March, 2001, conference discussing the future study of war, held at Penn State. Penn State has archived all available original material from the Correlates of War project, and is extending and enlarging the data collection efforts it began.

In 2002-2005, the project was led by Interim Director D. Scott Bennett and Associate Director Glenn Palmer. Paul Diehl served as the project’s Director from 2005 through 2012 and Zeev Maov served as Director from January 2013 until April 2022. In April 2022, Jeff Carter and Scott Wolford were named Co-Directors of the Correlates of War project. D. Scott Bennett serves as the project’s Associate Director, a position he has held since 2005.