During a war, the U.S. national leadership expects the military forces to conduct large-scale, sustained combat operations with the goal of winning quickly with as few casualties as possible. Interdiction missions are part of the strategy for achieving this goal. These missions are part of the effort aimed at denying the enemy sanctuary and freedom of action. Targets may include such things as tanks, bridges, and factories that when destroyed make opponents easier to attack and defeat. Combat aircraft have predominately been used to fulfill interdiction missions because they generally offer the versatility and capability to strike at the enemy when and where needed. In recent years, U.S. military services’ interdiction and other combat mission priorities have changed. During the Cold War, the enemy was more clearly identified, and defense forces were geared to fight that enemy. The threat has changed dramatically, from a single global threat to smaller, less defined regional threats, and the size and structure of defense forces are changing as well. As the services draw down their forces, the Department of Defense (DOD) is grappling with questions about how to maintain technological superiority over potential adversaries within expected budgets. During the Cold War, the national military strategy was to contain communism through nuclear and conventional deterrence. DOD emphasized aspects of military power most useful for that purpose, including standby nuclear forces that combined bombers and land- and sea-based missile systems, forward-deployed forces in Europe and Northeast Asia, and reinforcements ready to deploy from the United States. With the end of the Cold War and the collapse of the Soviet Union, the United States faces no immediate threat to its survival. Therefore, the national military strategy is being altered to meet new, lessened threats. For example, the President, Chairman of the Joint Chiefs of Staff, and the Secretary of Defense identified the involvement in two nearly simultaneous major regional conflicts (MRC) as the most demanding threat—one in the east, another in the west. In addition to preparing to counter these threats, DOD will more likely be distracted by less easily defined and smaller contingencies. The modernization of U.S. forces is considered vital to preserving the combat edge they now enjoy and to ensuring future readiness. The strategy cautions against making major modernization investments unless there is “substantial payoff.” DOD’s Defense Planning Guidance for fiscal years 1997-2001 states its commitment to developing an affordable, long-term modernization and recapitalization program. This program is to (1) inject new technologies to modernize existing platforms and upgrade mission capabilities, (2) introduce modernized replacements for existing systems that substantially upgrade capabilities and lower operation and support costs, and (3) field new systems for which there is no like item in the inventory. DOD asserted that introducing these capabilities should better leverage joint warfighting capabilities and, in some instances, allow consideration for making compensating reductions elsewhere in the force. In November 1993, Congress established the Commission on Roles and Missions of the Armed Forces to study the way the services allocate roles and missions, to consider alternatives, and to recommend changes to the process to better meet future needs. The Commission comprised civilian and retired military officials appointed by the Secretary of Defense in consultation with Members of Congress. In Directions for Defense (May 24, 1995), the Commission reported that while each service develops valuable capabilities, considering these capabilities jointly is key to effective future unified operations. As part of the national military strategy and as reported in the Secretary of Defense’s January 1994 Annual Report to the President and the Congress, the military services have planned for four phases of operations: halting the invasion, building up U.S. combat power while reducing the enemy’s, defeating the enemy, and providing post-war stability. Interdiction may play a role in the first three phases. The significance of the role may vary according to the circumstances. During phase 1, the services seek to quickly minimize the territory and strategic facilities the invader can capture and ensure that the threatened ally can continue its crucial role in the collective effort to defeat the aggressor. High priority missions for U.S. forces during this phase include direct attacks on advancing enemy forces; air defense and ballistic missile defense to protect rear areas; attacks on selected high-value strategic assets, such as centralized command and control sites; interdiction of lines of communication critical to the enemy’s offensive; and suppression of enemy air defenses. Once the enemy attack has been stopped, phase 2 begins, and U.S. and allied efforts focus on continuing to build up combat forces and logistics support in theater, reducing the enemy’s capacity to fight and ensuring that the enemy does not regain the initiative. During phase 3, U.S. and allied forces may mount a large-scale, air-land counteroffensive to defeat the enemy by attacking its centers of gravity, retaking territory it occupies, destroying its war-making capabilities, and successfully achieving other operational or strategic objectives. In many cases, U.S. forces would also threaten or carry out amphibious assault landings in the enemy’s rear areas. Following a U.S.-coalition victory, military forces remain in theater to ensure that the conditions that resulted in conflict do not recur. These forces may also help repatriate prisoners, occupy and administer some or all of the enemy’s territory, assist in reestablishing friendly governments in liberated areas, or ensure compliance with the provisions of a cease-fire agreement or peace accord. Under DOD Directive 5100.1, the Air Force is primarily responsible for air interdiction missions, but the Army, the Navy, and the Marines are expected to interdict enemy forces as a collateral mission. While the services do not limit interdiction to any particular area on the battlefield, they generally strike at targets beyond the close fire support area to avoid hurting friendly forces. In line with the changes proposed by the Commission on Roles and Missions, the services are working out how to better conduct joint operations. Joint commanders can use interdiction to divert, disrupt, delay, or destroy the enemy’s surface military potential before it can effectively be used against friendly forces. Military guidance on joint interdiction operations is still evolving, however. Joint Publication 3-0, entitled Doctrine for Joint Operations and issued in 1995, states that the services should fight together and cites examples of joint interdiction missions. The Air Force and the Army have draft joint doctrine publications that provide more details on how joint interdiction operations would work. Joint Publication 3-03, Doctrine for Joint Interdiction Operations, drafted by the Air Force, describes how the services should coordinate the use of their forces during the joint missions. The Army’s draft of Joint Publication 3-09, Doctrine for Joint Fire Support, describes how the services might better synchronize the use of firepower in all missions to ensure success. According to an official in the Office of the Joint Chiefs of Staff, these publications may be approved in the fall of 1996. During two major regional conflicts, U.S. military forces expect to encounter over 100,000 mobile or fixed targets. Mobile targets include tanks, personnel carriers, artillery, trucks, and missile launchers. Fixed targets include bridges, highways, railyards, fuel storage sites, and power production sites. Striking at various targets becomes more critical at different times during a war, depending on how the targets support the enemy or threaten friendly forces. For example, during phase 1 of a war, halting the enemy’s movement may make it critical for the services to interdict mobile targets such as tanks and artillery. The services’ weapons for interdicting targets include aircraft, missiles, and helicopters. Each service traditionally has individually determined the capabilities it needs to fulfill its missions. The Air Force, the Navy, and the Marines expect to use large portions of their combat aircraft for interdiction missions. These aircraft can also be used for other roles, such as close air support or air superiority. During the Gulf War, however, most of the combat sorties by U.S. attack aircraft were flown for interdiction missions (see table 1.1). In addition to fixed-wing aircraft, weapons such as the Navy’s Tomahawk Land Attack Missile (TLAM), the Army’s Tactical Missile System (ATACMS) and attack helicopters, and the services’ precision-guided munitions can also be used to interdict targets. To illustrate the need to compare the services’ plans for improving their interdiction capabilities, we evaluated (1) the services’ current and future aggregate interdiction assets for striking identified enemy targets and (2) the effect of the services’ planned modernization programs on total interdiction capabilities and alternatives to those programs. This report is one of a series of reports assessing how DOD might better adapt its combat air power to meet future needs. Other reports in this series address close fire support, air superiority, suppression of enemy air defense, surveillance and reconnaissance, and aerial refueling. To assess the services’ aggregate interdiction capabilities, we identified how the services plan to hit expected targets now and in the future. We relied on threat assessments by the Defense Intelligence Agency and the military services to identify the number and type of targets. We also reviewed doctrine of the Office of Joint Chiefs of Staff, the Air Force Doctrine Center, the Navy Doctrine Command, and the U.S. Army Training and Doctrine Command to identify how the services have been authorized to perform interdiction missions. Officials from the Office of the Secretary of Defense and from the Air Force, the Army, the Marine, and the Navy headquarters provided information on current interdiction capabilities and modernization plans.