Three contrary theories of great power war are examined. The first is the common balance of power argument that parity preserves peace. The second is Organski's oft-cited alternative, “the power transition.” The third is a conflation of the first and second. Like the first, the inherent inability to measure power precisely is the basis of the conflated balance of power theory. Like the second, the conclusion is that parity encourages war. Unlike either the first or second theory, the third provides an explanation of the incidence and extent of warfare between great powers. The basic proposition tested is that nonseparated great powers fight as they approach parity in power capabilities. The evidence is from the relations between the European great powers during 1815–1939.

Approximate parity in power capabilities between states creates uncertainty of victory if war were to occur. Whether, therefore, decisional uncertainty inhibits war between states or makes a breaking of the peace likely, is a central question in the host of ‘balance of power’ theories of interstate conflict. Some argue one way; others a different way; and some appear to argue one way, then the other. For along time each found support in armchair reflection—common sense bolstered with diplomatic anecdotes from ancient and modern state systems. Arguments could be made to command diverse historical examples because they rested upon the common assumption that calculations of power, security and conflicts of interest are essentially the same in any system of sovereign states. Anarchy, if you will, orders anachronisms. Now, however, each side can find support in quantitative evidence from far more systematic empirical analyses. The latter analyses are intended to bring some order and discipline to contrary insights by replacing anecdote with data.

John Vasquez, in a recent number of the Review, attempts to document the two-part ‘claim that the Realist paradigm has dominated quantitative international relations and has to this time (1979) failed.to explain (state) behaviour adequately’. He labels this the ‘colour it Morgenthau thesis’.