of War Project
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.
Paul Diehl - Current Director
University of Illinois
Dept. of Political Science
361 Lincoln Hall
702 S. Wright St. Urbana, IL 61801
The Correlates of War Project was founded in 1963 by J. David
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
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 (see Data
Sets). In addition to the collection of data, the project has conducted
many empirical studies (see Bibliographic Essay) about war and conflict.
An important progeny of the project is the BCOW (Behavioral Correlates
of War) 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.
As of November, 2002, the project continues under the leadership of
Interim Director D. Scott Bennett, and Associate Director Glenn Palmer.
As of January 2005, the project continues under Director Paul
Diehl, and Associate Director D. Scott Bennett.
Participating Institutions: International Alliances: Doug
Gibler, University of Kentucky - Intergovernmental Organizations:
Timothy Nordstrom, University of Mississippi; John Pevehouse, University
of Wisconsin - Territorial Change: Paul Diehl, University of Illinois -
Direct and Colonial Contiguity: Paul Hensel, Florida State University -
Interstate and Extrastate War: Meredith Sarkees, Saint Mary's
University; Frank Wayman, Wayne State University - Intrastate War: Jeff
Dixon, Wright State University; Meredith Sarkees, Saint Mary's
University. - Culture: Errol Henderson, Penn State University -
Militarized Disputes: Glenn Palmer, Penn State University
Advisory Board / Host Liaisons: International
Alliances: James Ray, Vanderbilt University - Intergovernmental
Organizations: Brian Pollins, The Ohio State University - System
Membership: Paul Diehl, University of Illinois - Geopolitical Units:
Paul Diehl, University of Illinois - Interstate, Intrastate, and
Extrastate War: Paul Hensel, Florida State University - Culture: James
Ray, Vanderbilt University - Militarized Disputes: Brian Pollins, The
Ohio State University
Objectives: The Correlates
of War project seeks to facilitate the collection, dissemination, and
use of accurate and reliable quantitative data in international
Key principles of the project include a commitment to standard
scientific principles of replication, data reliability, documentation,
review, and the transparency of data collection procedures.
More specifically, we are committed to the free public release of
data sets to the research community, to release data in a timely manner
after data collection is completed, to provide version numbers for data
set and replication tracking, to provide appropriate dataset
documentation, and to attempt to update, document, and distribute
follow-on versions of datasets where possible. We intend to use our
website as the center of our data distribution efforts, to serve as
central site for collection of possible error information and questions,
to provide a forum for interaction with users of Correlates of War data,
and as a way for the international relations community to contribute to
the continuing development of the project.
Ongoing Research: The Correlates of War project seeks to
expand available data for IR research in two ways. First, we have a
number of projects ongoing "in house." Second, we are
encouraging scholars within the Correlates of War community to engage in
guided research through the Data Hosting Program.
This page lists projects and activities ongoing under the COW rubric.
Highest Priority: Dyadic
War Data: We are currently working to identify, in each multilateral
interstate war, which states actually engaged each other militarily, and
at what level of violence (e.g. did not interact, declared war, had
air/ground combat only, engaged each other extensively). Work proceeding
in conjunction with Resat Bayer, Koc University and College of Wooster.
Lower Priority: Diplomatic Relations: Patterns of diplomatic representation tell us a
lot about the status ordering and lines of communication in the
interstate system. Beginning in 1817, information about diplomatic bonds
between states at 5-year intervals is contained in this data set.
Geopolitical Units: While a key element of the international system
since 1816, formal and recognized states have not always covered the
globe in the manner they largely do today. This data set traces the
status of non-state territorial units in the system, including colonies,
mandates, autonomous territories, and so on, their relationship, and
their eventual incorporation in/transformation to states.
Ongoing hosted projects: Cultural Attributes of States: Cultural differences between and
within states are thought by some to contribute to conflict. In
order to test these speculations a data set delineating the
linguistic, religious, and ethnic composition of states was created.
It records this information for all states at 10-year intervals from
1820 to 1990. Hosted by Errol Henderson, Penn State University.
Interstate/Extrastate War Data: We are currently working to
update the interstate war data through 2003, through the auspices of
data set hosts Meredith Sarkees, Saint Mary's University, and Frank
Wayman, Wayne State University.
Intrastate War Data: We are currently considering updates,
extensions, and some possible redefinitions in the intrastate war data,
through the auspices of data set hosts Jeff Dixon, Wright State, and
Meredith Sarkees, Saint Mary's University.