Birds of a Feather: Democratic Political Systems and Alliance Choices in the Twentieth Century

An examination of the alliance choices of democratic states between 1920 and 1939 and between 1946 and 1965 is undertaken to answer the question, do democracies have a tendency to ally with each other more than they ought to according to probability? The analysis of the data indicates that during the first period there was an initial tendency for democratic states to ally with each other at a higher rate than probability indicates should have been the case, but that the overall level of democratic alliances decreased as the rate of their existing alliances dissolved and democracies sought other types of partners. During the period from 1946 to 1965 alliances between democracies were formed and maintained at much higher rates than probability indicates should have been the case. Further analysis demonstrates that this effect is probably not significantly affected by either the effects of previous wartime alliances or geography.