This dissertation examines how congressional deliberation over the constitutionality of a use of force affects the war power relationship between the president and Congress. In particular, it presents empirical data on whether and how Congress exerts its attempts to control presidential war power through deliberation, on the limits of congressional ability to regulate a war, on historical patterns of the presidential unilateral use of force, and on the institutional conditions for good congressional deliberation. My main argument is that congressional deliberation over the constitutionality of a use of force is a primary influence on Congress's ability to exert its will through the passage of legislation to check the president's use of force. I focus on congressional floor debates recorded in the Congressional Record (1989-2009) over different use of force events occurring from 1989 to 2003. These incidents are collected from the Correlates of War Project Dataset. I cluster 229 congressional deliberations on the constitutionality of the use of force and bills thereof into 14 military events according to the war timeline depicted by the Correlates of War Project Dataset. In response to the main research question, I present three empirical models. The first empirical model demonstrates that a higher level of congressional deliberation over a use of force influences Congress to impose a higher level of control over presidential war power. The second model demonstrates that as long as Congress imposes control over a military deployment, the president systematically resists that control. Although the second model demonstrates that congressional attempts to check presidential war power cannot prevent the president from taking unilateral military action, I argue that this result suggests that it is even more important for Congress to have better deliberation and to try to impose a check on the president, which can create an unequivocal legal and political accountability for the president. Therefore, I present the third empirical model to demonstrate that congressional rule-setting, including referral of a bill to committee, an adoption of open-rule floor debate, and deliberation over a non-annual budget bill, is the primary factor determining the quality of congressional deliberation.