The Missile Defense Agency has been charged with developing and deploying ballistic missile defenses against threats posed by adversaries from all geographic regions, at all ranges, and in all phases of flight. At least 25 countries have acquired ballistic missiles, including many countries that are also seeking or have acquired weapons of mass destruction that could be used on these missiles. In response, the Missile Defense Agency has been developing defenses against short-, medium-, intermediate-, and intercontinental-range ballistic missiles that could be targeted against U.S. forces abroad, U.S. friends and allies, and the U.S. homeland. For example, the Terminal High Altitude Area Defense system, Patriot Advanced Capability-3, and Aegis Ballistic Missile Defense system are being developed primarily to provide an integrated capability to defend deployed U.S. forces, friends, and allies against short- and medium-range ballistic missiles. The Missile Defense Agency is also developing sea-based defenses to destroy short-range missiles in the terminal phase of flight in order to defend deployed forces. In addition, the Missile Defense Agency is developing a Ground-based Midcourse Defense system designed to destroy intercontinental-range ballistic missiles targeted against the U.S. homeland, deployed U.S. forces, friends, and allies. Some ballistic missile defense systems are being designed to defend against more than one type of threat. For example, the Aegis Ballistic Missile Defense system is being designed not only to defend deployed U.S. forces, allies, and friends from short- and medium-range missiles, but also to help defend the U.S. homeland from longer range missiles. Table 1 summarizes the threat categories to be addressed by U.S. ballistic missile defenses. While the Missile Defense Agency is responsible for developing missile defenses, the unified combatant commands are the military organizations primarily responsible for deterring attacks and for employing forces should deterrence fail. The Unified Command Plan, which is signed by the President, establishes the combatant commanders’ missions and responsibilities and establishes their geographic areas of responsibility. The most recent version of the Unified Command Plan, which was published in 2006, identified five combatant commands—U.S. Central Command, U.S. European Command, U.S. Northern Command, U.S. Pacific Command, and U.S. Southern Command—with responsibilities covering specific geographic regions. For example, U.S. Northern Command’s area of responsibility includes all of North America and surrounding waters; for missile defenses, U.S. Northern Command would have primary responsibility for defending the continental United States from an intercontinental-range missile attack. U.S. Strategic Command is a unified combatant command with responsibilities to integrate global missions and capabilities that cross the boundaries of the geographic commands. Initially assigned responsibility for nuclear deterrence, space, and computer network operations, the President, in January 2003, expanded the command’s responsibilities to include several missions not previously assigned to a combatant command. These missions were: global strike planning and execution; planning, integrating, and coordinating global missile defense (including missile defense advocacy); oversight of intelligence, surveillance, reconnaissance, and global command and control; and DOD information operations. In January 2005, the Secretary of Defense also assigned the command responsibility for integrating and synchronizing DOD’s efforts in combating weapons of mass destruction. DOD envisioned that U.S. Strategic Command’s global operations would potentially add value to the geographic combatant commands as they carried out their responsibilities, and provide the President and Secretary of Defense with an expanded range of military options for responding to future threats. U.S. Strategic Command and the Missile Defense Agency created the Warfighter Involvement Process in 2005 to accomplish U.S. Strategic Command’s responsibility to advocate for desired global missile defense characteristics and capabilities on behalf of all combatant commanders. Additionally, U.S. Strategic Command envisions using the process as a way for the military services and the Joint Staff to provide the Missile Defense Agency with guidance and advice on desired ballistic missile defense capabilities, operational approaches, and suitability and supportability features. The Warfighter Involvement Process is intended to provide a collaborative forum for the combatant commands, U.S. Strategic Command, Joint Staff, and military services to identify, assess, and articulate capability needs to the Missile Defense Agency, analyze the risks associated with capability gaps and redundancies, and examine possible solutions and implementation timelines. Although the Warfighter Involvement Process involves a variety of organizations, U.S. Strategic Command is responsible for administering and managing the various analytical activities, software tools, focus groups, and review boards that make up the process. GAO has previously reviewed DOD’s plans to operate ballistic missile defense systems as certain systems have transitioned from a research and development emphasis to operational military capabilities. For example, in 2006 we assessed DOD’s preparations to operate and support ballistic missile defenses that are under continuous development. In 2007, we reported that DOD’s long-term plans to develop boost and ascent phase missile defense systems did not consider operational perspectives on how many of these systems would be required for various deployment periods, or the challenges of establishing bases at potential deployment locations. Additionally, in response to a congressional mandate, we have annually reported since 2003 on the cost, schedule, testing, and performance progress that the Missile Defense Agency is making in developing ballistic missile defenses. U.S. Strategic Command and the Missile Defense Agency created the Warfighter Involvement Process in 2005 to identify and address the combatant commands’ ballistic missile defense capability needs, but the process has yet to overcome key limitations to its effectiveness. Although the Warfighter Involvement Process is still evolving, it has helped the Missile Defense Agency address some of the combatant commands’ needs. However, even as U.S. Strategic Command and the Missile Defense Agency move forward with the process, they have not finalized the implementation guidance needed to clarify their respective roles and responsibilities; have not yet established effective methodologies for identifying, prioritizing, and addressing combatant command needs; and have not involved senior civilian DOD leadership to adjudicate potential differences among the combatant commands’ priorities and provide a departmentwide perspective about how to best allocate resources. As a result, DOD is at risk of not addressing the combatant commands’ missile defense needs if improvements are not made that establish an effective and well documented process and provide a DOD-wide perspective when prioritizing these needs. Although the Warfighter Involvement Process was created in 2005 and is still evolving, the process has helped the Missile Defense Agency to address some combatant command ballistic missile defense capability needs. Since 2001, DOD has emphasized a capabilities-based development strategy to provide the combatant commands with the capabilities they require to deter and defeat a broad range of adversaries. By establishing the Missile Defense Agency in 2002, DOD intended to follow a more streamlined capabilities-based development strategy to rapidly develop and field ballistic missile defenses. Through the Warfighter Involvement Process, the agency has addressed some of the combatant commands’ capability needs in developing ballistic missile defenses. However, because the Warfighter Involvement Process is still evolving, the combatant commands have not yet formally determined the extent to which the agency’s plans are in line with the commands’ needs. The Warfighter Involvement Process has not fully evolved to effectively convey either the commands’ priorities to the Missile Defense Agency or the Missile Defense Agency’s planned adjustments back to the commands. When the Secretary of Defense created the Missile Defense Agency in 2002, DOD lacked a process for the agency to consider the combatant commands’ priorities as it developed ballistic missile defenses. Instead, the Missile Defense Agency focused on developing and deploying capabilities based on its own technology-driven assessment of what could be fielded quickly in order to meet the President’s direction to quickly field a limited ballistic missile defense system by 2004. As a result, the Missile Defense Agency expedited its initial designs and development plans without formally considering the combatant commands’ needs, according to the DOD Inspector General. Additionally, the agency identified long- term ballistic missile defense system capability goals before having a process in place to identify the commands’ capability needs. In emphasizing the rapid initial development of ballistic missile defense systems, the Missile Defense Agency anticipated that further investments could be needed to better meet the combatant commands’ requirements. Under the Secretary of Defense’s 2002 direction, the Missile Defense Agency’s approach has been to deploy capabilities early, which may only partially meet warfighter needs, and then incrementally improve the deployed capabilities’ effectiveness by inserting new technologies as they become available and as the threat warrants. To initiate this approach, the agency focused on further developing ballistic missile defenses that had been previously under development by the military services and subjected to DOD’s traditional joint requirements determination process. Officials from U.S. Strategic Command, U.S. Northern Command, the Missile Defense Agency, and the Office of the Secretary of Defense told us that the agency’s approach resulted in the rapid deployment of operational missile defenses. A senior Missile Defense Agency official added that the Secretary of Defense reviewed and approved the agency’s plans for developing this initial defensive capability. However, absent the combatant commands’ inputs, U.S. Strategic Command concluded in January 2005 that taking this approach made it difficult not only for the Missile Defense Agency to associate its actions with the commands’ requirements, but also for the combatant commands to evaluate the agency’s progress. According to U.S. Strategic Command, the lack of a process also created the potential for inefficiencies and unnecessary redundancies in the Missile Defense Agency’s investments, resulting in increased risk to the baseline costs and operational effectiveness of the ballistic missile defense systems under development.