"For over a century the U.S. military has focused on expeditionary warfare overseas. Its participation in domestic operations has been sporadic and generally in response to natural disasters. With the heightened concern about large-scale terrorism, have come efforts to involve DOD [Department of Defense] more closely with federal, state and local agencies in their homeland security activities. DOD resources are unique in the government, both in their size and capabilities, and can be applied to both deter and respond to terrorist acts. While the DOD leadership is ready and willing to play a supporting role in these efforts, it wishes to maintain overseas military operations as the Department's primary focus, and avoid an inadvertent drain of fiscal, materiel, and personnel resources to the homeland security mission. In response to the increased focus on homeland security, on October 1, 2002, DOD activated a new combatant command, Northern Command or NORCOM [Northern Command]. At the same time, Congress and the Administration are working to create a new statutory Department of Homeland Security (DHS). Exactly how DOD and a new DHS will establish and maintain coordination and cooperation remains to be seen. Legislation currently under consideration (H.R. 5005 and S. 2452) to create the new DHS is silent on this question, and details on the new NORCOM are scarse. The intelligence collection and analysis capabilities within the Department of Defense are a substantial portion of the United States' national intelligence assets. They include the National Security Agency, the National Reconnaissance Office, the National Imagery and Mapping Agency, the Defense Intelligence Agency, and the intelligence and security branches of the individual armed services. Consequently, the means and extent of cooperation/coordination between DOD and the new DHS will be of great importance to the success of DHS's efforts to provide comprehensive intelligence analysis."
CRS Report for Congress, RL31615