Among the issues being considered during the Pentagon's Quadrennial Defense Review (QDR)--a mandatory report to Congress on strategy, capabilities, and resources--is reassessing the military's role in homeland security. In determining what the armed forces need, recent international events offer important insights, particularly for medical support, security forces, and infrastructure protection and recovery.

Preparing for the Worst. The tsunami that struck Southeast Asia, the Chechen terrorist attack on a school in Beslan in Russia, and the destruction of critical infrastructure in Iraq are not events likely to take place in the United States anytime soon, but they are reminders that such terrible things can happen. They also hold lessons for the QDR. Each in its own way was a tragedy on an unanticipated scale. The response was ad hoc, and the results were inefficient. Homeland security challenges faced by the United States might be of similar character.

Most disasters, including terrorist attacks, can be handled by emergency responders. Only catastrophic disasters--events that overwhelm the capacity of state and local governments--would require a large-scale military response. The military should be well-organized, trained, equipped, and exercised for this type of mission. However, the Pentagon should not wait until lives and property are at stake to assess its preparation for catastrophic response.

Assigning this mission to the military makes sense. It would be counterproductive and ruinously expensive for other federal agencies, local governments, or the private sector to maintain the excess capacity and resources needed for immediate catastrophic response. On the other hand, maintaining this capacity would have real utility for the military. The Pentagon could use response forces for tasks directly related to its primary warfighting jobs--such as theater support to civilian governments during a conflict, counterinsurgency missions, and postwar occupation--as well as homeland security. Furthermore, using military forces for catastrophic response would be in accordance with constitutional principles and would not require changing existing laws.

Makeup of the Force. These forces would mostly be National Guard soldiers, troops that have the flexibility to work equally well under state or federal control. The force needs to be large enough to maintain some units on active duty at all times for rapid response and sufficient to support missions at home and abroad. For catastrophic response, three components would need to be particularly robust: medical, security, and critical infrastructure response.

Medical Units. In December 2004, a tsunami struck Southeast Asia and Africa without warning, killing almost 200,000. It was an example of the kind of destruction to expect from a catastrophic disaster. The United States does not have the capacity to mass medical assets for tsunami-level casualties. The current defense medical support available for homeland security is too small and ill-suited for the task. Rather than field hospitals that take days and weeks to move and set up, the military needs a medical response that can deal with thousands of casualties on little notice, deploy in hours, assess and adapt existing structures for medical facilities, and deliver mass care to people in place rather than moving them to clinical facilities.

Security Forces. In September 2004, a large group of well-armed terrorists held 1,181 people hostage at a school in Beslan, Russia. Hundreds died in the rescue attempt. The disastrous result illustrates the likely outcome of ad hoc military response against a large-scale terrorist attack in a civilian community.

Virtually no American community is prepared to deal with a platoon or more of well-armed and well-coordinated terrorists. Such a nightmare scenario would require a military response using specially trained and equipped personnel who are practiced at working with civilian agencies. These troops should prove equally adept at conducting counterinsurgency operations in urban terrain overseas, where neutralizing the enemy and protecting civilian lives and property are equally important.

Critical Infrastructure. In the wake of the Iraq War, U.S. forces found that years of neglect and a mounting insurgency had decimated Iraq's infrastructure. No aspect of the occupation was more ad hoc and poorly planned than efforts to reconstitute critical infrastructure. Projects were poorly managed, large numbers of contracts were let without adequate oversight, and U.S. forces did not coordinate the necessary security. The results leave little hope that the military, as currently structured, would be of much utility in restoring critical national infrastructure after a catastrophic disaster at home or overseas.

However, the means to conduct these missions are available. The U.S. military has the command, control, and security assets; the U.S. Army Corps of Engineers has the capacity and expertise to manage large-scale contracts under difficult, stressful conditions; and the Federal Emergency Management Agency (FEMA), which frequently partners with the military for disaster response, has the expertise to conduct needs assessments and coordinate community recovery. Response teams reinforced with a large cadre of Reserve contracting officers could be paired with the Corps of Engineers and FEMA to provide an effective infrastructure protection and recovery force for disasters at home or overseas.

Force for the Future. These units would not be homeland defense forces or humanitarian peacekeeping or peacemaking troops. Military force should be used only for matters of vital national interest. That standard would apply to these units as well. They would support major operations overseas and catastrophic disasters at home.

The QDR should be used to determine the precise number of the forces that are required and how they can be established by converting the existing Cold War force structure into units that are appropriate for new missions overseas and at home.

James Jay Carafano, Ph.D., is Senior Research Fellow for National Security and Homeland Security in the Kathryn and Shelby Cullom Davis Institute for International Studies at The Heritage Foundation.