It is quite possible that after the events of 11 September 2001, the roles and missions of the Department of Defense in the area of Homeland Security are destined for change. This monograph provides and examination of the legal, and traditional aspects of Homeland Security in the U.S. and the current framework for managing a domestic Weapons of Mass Destruction (WMD) incident. Understanding the past roles and missions of the DoD in regard to Homeland Security are relevant as the Office of Homeland Security (OHS) formulates a comprehensive national strategy for Homeland Security. Throughout the Nation's history, the American public has consistently equated Homeland Security with the Armed Forces. Immediately following the 11 September attacks there was confusion among many in the U.S. government as to which federal agency was responsible for Homeland Security. Several key members of the Senate Armed Services committee expressed concern over the current security framework and the DoD's supporting role in domestic Homeland Security. This monograph addresses these issues through an examination of the DoD's (Armed Forces) historical role in the defense of the nation as well as its role in domestic support operations. The monograph begins with a brief analysis of the emerging threats that the United States faces, and offers a proposed definition for Homeland Security. This is followed by an examination of the evolution of legal considerations when employing federal military forces in a domestic support capacity. It addresses the Posse Comitatus Act and recent refinements to the Act that circumvent its provisions in instances of clearly identified threats to the Nation's interests. The second chapter includes an analysis of Civil Defense and the DoD's participation in past Civil Defense missions. A chronology of Civil Defense in America is included beginning with post World War I activities up through the present time. This analysis illustrates that in time of crisis, when the public feels vulnerable, they look to the DoD for security. The monograph outlines the current DoD supporting role to both the FBI for Crisis Management and to the FEMA for Consequence Management during a WMD incident. The monograph argues that the current system is adequate and the DoD should not be designated as the LFA for WMD incidents. The monograph recommends the creation of a new Commander-in-Chief (CINC) for Homeland Security. This CINC should also be charged with the responsibility of developing the campaign for, and executing the global War on Terror. Additional recommendations include some minor changes to both Joint and Army doctrine in regard to Homeland Security. It also recommends that the DoD maintain a receptive attitude towards new domestic missions, advocating the temporary execution of non-traditional missions.