The main objective of this investigation is to develop a better understanding of the domestic and international conditions under which state leaders: 1) decide to come to the defense of other states that face security threats (why they adopt policies of extended deterrence), and once extended deterrent policies are in place, b) when will adversaries challenge the security commitments of such states. The researcher will test two alternative theoretical models of state behavior against the historical evidence of Great Power extended deterrence cases over the past 170 years to determine what conditions have had a consistent and strong effect on the decisions of state leaders. The first model will test hypotheses which posit that foreign policy decisions are driven largely by assessments of geo-strategic interests and relative military power. In contrast, the second model proposes that foreign policy decisions are driven fundamentally by domestic political and economic concerns and, as a result, national security policy cannot be separated from the goal of political leaders to secure and strengthen their position of domestic political power and authority. The hypotheses from each model will be tested by statistical analysis and the results will address a number of more specific questions which are of both scholarly and policy importance, such as: a) when are states likely to form alliances?; b) when are adversaries likely to question the extended deterrent value of an alliance?; c) when will alliance partners honor their deterrent commitments?; and, d) under what conditions can we expect domestic political concerns to shape national security policy in fundamental ways?
