The preamble of the Constitution sets out six reasons for its institution, among which two stand out: the establishment of justice and the provision of common defence. The national security of the United States was of paramount importance to our founders and remains so today more than 200 years later. While there is no clear answer as to how to achieve security, our system of constitutional government provides the framework for pursuing its ends. The Constitution itself, in its ambiguity and deliberate need for interpretation, along with elements of power-sharing and the rule of law, play a key role in how our government provides security coverage for our nation. This article will explore how these elements complement and contrast each other in providing our government leaders with the tools to achieve national security. The division of power is one of the most often cited principles of our constitutional system. For example, in terms of foreign policy, the Senate must provide advice and consent to the president when making treaties and appointments. Instead, the Constitution gives Congress the authority to declare war and provide military funding while the President acts as commander in chief of the armed forces. This power-sharing creates friction between the executive and legislative branches when they disagree and “is an invitation to fight for the privilege of directing American foreign policy.” To function, our government must be able to resolve conflicts that arise as a result of this "fight." The rule of law is the principle that enables reconciliation and its primacy for the successful implementation of our government cannot be underestimated. Simply put, in the middle of the paper, the judiciary will continue to play a vital role in the "struggle" for power in foreign affairs and the use of armed forces. We will certainly see public debate and congressional involvement over President Obama's recent decision authorizing the "targeted killing" of a U.S. citizen abroad without due process under the guise of fighting terrorism. In conclusion, our Constitution developed a framework that articulated the necessary amount of government that “secured the blessings of liberty” while recognizing the dynamic institutions it created and the need for interpretation. National security will remain our government's primary duty; and the Constitution's ambiguity, separation of powers, and legal supremacy will ensure that our nation's policies and actions are rooted in situational context and always open to public scrutiny and debate.