An extension of the correlates of war formal alliance data set, 1648--1815

Arguing that most empirical studies of war arbitrarily limit themselves to analyses of the state system after 1815, this paper develops extensions of the Correlates of War formal alliance and system membership data sets from 1648 to 1815. An initial comparison of summary statistics indicates that alliance patterns in the post‐Westphalian period were similar, in most respects, to the alliance patterns of the nineteenth and twentieth centuries. However, inclusion of the new alliance data in re‐analyses of alliance war‐proneness (Levy, 1983) and alliance polarization (Wayman, 1984) show that the often noted inter‐century difference between the nineteenth and twentieth centuries may be exaggerated. Nineteenth century alliances were not less likely to be followed by war than alliances formed in other centuries.