Traditional approaches to questions of executive war power emphasize presidential-congressional relations, and focus on the meaning and implications of specific constitutional clauses. This dissertation offers an alternative approach by examining executive war power through the higher, more normative purposes to which the Constitution aims. It views executive war power from the perspective of Constitution's basic but essential goal of self-preservation, and argues that the Presidency has a unique duty to preserve, protect, and defend the Constitution. Presidential power, therefore, should be viewed in light of its duties to preserving the constitutional order. Presidential power, however, should not be viewed as "anything goes" for, true to republican principles, the people ultimately are sovereign and have multiple constitutional means by which to hold their leaders accountable. The dissertation focuses its analysis on the Constitution's text, examining Publius and other writings of the Founding era, to help uncover the explicit purpose and implicit principles for understanding the Constitution. Understanding "to what end" the Constitution aims provides the lens through which we should view the actions of its institutions and officers. The dissertation then offers an interpretative analysis of President Washington's words and deeds during the Whiskey Rebellion, demonstrating that his construction of the executive war power offers an important contribution to U.S. constitutionalism. It also focuses on Lincoln's construction of the executive war power during the Civil War, arguing that although Lincoln exercised extraordinary power in meeting the necessity of the situation, he did so while remaining true to both the spirit and the letter of the Constitution. This counters conventional opinions that Lincoln's conduct was un- or extraconstitutional, or that he had to act outside of the Constitution in order to save it. The dissertation suggests that the constitutionalism and statesmanship of Washington and Lincoln offer much perspective for understanding issues surrounding the executive war power today.