The Department of Defense defines overseas presence as the right mix of permanently stationed forces, rotationally deployed forces, temporarily deployed forces, and infrastructure required to conduct the full range of military operations. Historically, these forces have been concentrated in three regions--Asia-Pacific, Europe, and Southwest Asia. Forces in Europe include the major elements of two Army divisions; six Air Force wings, which include fighter/attack, refueling, and transport aircraft; one Navy aircraft carrier battle group; and one Marine Corps amphibious group. Prepositioned items include Army stockpiles of equipment for three heavy brigades, equipment and supplies for the lead unit of a Marine Corps expeditionary unit, and six Air Force air base support sets. The Mobility Requirements Study 2005, issued in January 2001, determined the number and mix of mobility systems needed to support the national defense strategy at the time, which required the military to fight and win two nearly simultaneous major wars. This mix includes both airplanes and ships owned by Defense as well as volunteer and chartered civilian airplanes and ships that participate in the Department's mobility programs. The study investigated mobility requirements stateside as well as between theaters and within individual theaters of war. The analysis determined requirements for the three components of mobility (airlift, sealift, and ground transportation) and assumed that most forces and prepositioned equipment currently stationed overseas, including those in Europe, would remain at the levels planned, at the time of the study, for fiscal year 2005. The study also modeled the en-route airbases needed to support the movement of forces and equipment. The study did not model any scenarios without forward-deployed U.S. troops and equipment in Europe. The study did conclude, however, that the mobility force structure planned for fiscal year 2005 was sufficient to fight and win one major theater war and that a second nearly simultaneous war could be won by shifting air and sealift mobility assets from one theater to the other. During the time of our study, the Department of Defense was conducting the Quadrennial Defense Review, a congressionally mandated review of national defense strategy, which is to analyze, among other things, force structure and military infrastructure. The review's report, issued on September 30, 2001, stated that the mix of new threats and missions requires the Department to reevaluate the Mobility Requirements Study 2005 in detail and adjust the results as necessary. According to a Department official, this reevaluation includes the en-route basing system, the use of civilian aircraft, and the mobility requirement for the new national defense strategy. A U.S. forward presence in Europe reduces mobility requirements, mobility costs, war-fighting risk, and time required for deployment to operations in Europe or Southwest Asia. A reduction in any of the four elements of forward presence in Europe would have an adverse effect on mobility requirements, costs, and risk, according to Defense officials. Central Command officials have told us that the U.S presence in Europe, particularly the en-route system of airbases and the Air Force assets, would be critical to the success of their operations in Southwest Asia.European Command officials also told us that the U.S. presence allows the Commander to manage the missions assigned to the Command more easily, such as the small-scale contingencies in Bosnia and Kosovo. Many officials generally agreed that some elements have a greater relative impact on mobility requirements than others. DOD officials suggested a relative ranking of U.S. military presence in Europe starting with the en- route system of airbases as having the greatest impact on mobility, followed by prepositioned equipment, Air Force aircraft and personnel, and finally Army combat forces. The Department of Defense maintains a system of en-route airbases in Europe and the Pacific to support long-range airlift operations. These bases provide the basic services, such as parking facilities, maintenance capabilities, equipment to load and unload cargo if needed, and refueling capabilities for airlift aircraft as they move on to their final destinations. Six airbases in Europe are part of this en-route system (see fig. 1). Officials from the commands agreed that the en-route system is critical to operations in Europe and Southwest Asia. The en-route airbase system in Europe gives transport aircraft the ability to fly from the U.S. to Europe and continue from Europe into Southwest Asia in the early phase of a conflict, a range of about 3,500 nautical miles, which is about the distance a C-17 can fly without refueling. Defense officials believe that the system has a significant impact on their ability to move troops and equipment into any location around the world. For example, the loss of Howard Air Force Base in Panama made it more difficult for the United States to move forces quickly and easily into Central and South America. According to Defense officials, if the en-route airbase system in Europe did not exist, it would have to be created before combat forces and equipment can arrive from the United States and move through on their way to an operation in Europe or Southwest Asia. This effort would require using airlift to open airbases along the way, instead of using the same airlift to carry troops and equipment. Without the system, the Department would require more air refueling capability, as well as more airlift. The Mobility Requirements Study 2005 concluded that en-route system capacity is significantly less than requirements but that planned improvements would largely eliminate the shortfall by 2005. Defense transportation officials attribute the shortfall to the shrinkage in U.S. overseas presence and increased reliance on the remaining bases. They believe that the shortfall would cause forces and equipment to arrive in the war theater later than planned, increasing the risk of operations not being executed as planned and the risk of higher casualties. We recently issued a report on the en-route system. This report discussed the system's shortfall in capacity, the reasons for the shortfall and costs associated with improvements, and the lack of basic information and a coherent management structure to ensure that the operations of the system can be carried out efficiently and effectively. We are continuing to study the system's planned modernization. According to U.S. Transportation Command officials, the en-route system will continue to be evaluated in the context of the new defense strategy. They stated that they anticipate airlift requirements will be at least as demanding, and possibly more demanding in the new strategy. The services have both land-based and sea-based equipment and munitions prepositioned in Europe. Land-based prepositioned items consist of equipment and supply sets for three Army brigades, one Army artillery battalion, and one Marine expeditionary unit, in addition to six Air Force air base support sets and other Air Force equipment. The Army's three brigade sets, two in central Europe and one in Italy, include 348 Abrams tanks and 240 Bradley fighting vehicles. In Norway, the Army has equipment for an artillery battalion, which includes 18 self-propelled howitzers, and the Marine Corps stores equipment and 30-day supplies for a Marine expeditionary brigade. Air Force air base support sets-- temporary shelters for early-arriving air base personnel--are stored at a site in Luxembourg, with the other equipment stored in sites around Europe. There are also ships afloat in the Mediterranean Sea, which carry equipment and munitions for the Marine Corps and the Air Force (see fig. 2). Prepositioned equipment in Europe greatly reduces the amount of time needed to deploy to a conflict in Europe than if the same forces and equipment have to be moved from the United States using air and sealift. For example, officials stated that the Army has established a brigade set of equipment in Bosnia for rotating troops to use when they deploy to that mission instead of bringing their own. Using this prepositioned equipment saves about $5.5 million in transportation costs if the unit is coming from the United States and about $2.5 million if the unit is based in Europe. Furthermore, an earlier mobility study pointed out that prepositioned equipment is a more attractive option because it might be less expensive than purchasing more airlift aircraft. The Mobility Requirements Study 2005 assumed both afloat and land- based prepositioned equipment would be in place and fully stocked in 2005 and did not model any scenarios without it. Land-based prepositioned equipment in Europe is not used to support the two major theater war strategy. However, some prepositioned equipment can be used as reserve during a major conflict or in small-scale contingencies. In fact, from the start of the mission in Bosnia in December 1995 to June 1998, the Army lent over 7,900 pieces of prepositioned equipment to units in Bosnia. The equipment included, among others, Abrams tanks, Bradley fighting vehicles, and armored personnel carriers. Officials did cite some drawbacks to having large quantities of equipment and weapons prepositioned in specific places. First, it is always difficult to plan conflicts in advance, and there is always the danger that the equipment may be in the wrong place or that two conflicts break out at the same time. Other risks are that prepositioned equipment can be a tempting target for enemies and that the Department might need more flexibility to quickly move to other geographical regions than prepositioning allows. The Air Force has almost 33,000 personnel in Europe assigned to six wings, which include three fighter wings, a refueling wing, an airlift wing, and a multi-mission wing (see fig. 3). These forces can accomplish all the traditional Air Force missions, both conventional and nuclear. The units include 167 fighter/attack aircraft, 36 transport aircraft, and 15 refueling aircraft. Air Force aircraft deployed in Europe allow forces to move more quickly to small-scale contingencies and reduce the burden on airlift and sealift. For example, F-15 pilots from Aviano Airbase in Italy conducted combat missions during the first day of the air campaign in Kosovo. Also, the 31st Fighter Wing based at Aviano is providing the aircraft to support the mission to monitor, control, and police air space over Bosnia. Central Command officials stated that combat and transport aircraft are important to have in Europe and are critical to ensuring the command's ability to execute its operational plan for a major theater war in Southwest Asia. As stated above, the Mobility Requirements Study 2005 modeled the forward-deployed forces in Europe as they were planned for fiscal year 2005. The exception is the assumption that those forces currently enforcing the "no-fly" zones in Northern and Southern Iraq would no longer be assigned to those missions and therefore would no longer be forward deployed in Europe. This would mean that there would be fewer Air Force personnel and equipment stationed in Europe and a greater mobility requirement for U.S. Central Command to execute their operational plan if a conflict were to arise in Southwest Asia. There are about 69,400 soldiers based in Europe who are assigned to three infantry and three armored brigades, an aviation brigade, and numerous support units (see fig. 4). Some officials we spoke with stated that, of the four elements of forward presence, Army combat and support troops would be the easiest to move, if they were not forward deployed in Europe. In the event of a conflict in Europe or Southwest Asia, 95 percent of ground troops would move by commercial airlift. These troops would then fall in on prepositioned equipment or meet up with their unit equipment, which would move by sealift. According to the Mobility Requirements Study 2005, there is sufficient sealift, except for special purpose sealift, which is used to move watercraft that cannot self-deploy, to handle the requirements of a two major theater war strategy. This would leave the Defense-owned transport aircraft to carry other critical items. But having Army personnel and equipment stationed in Europe allows the Commander, U.S. European Command, to deploy troops faster and easier to a conflict in his theater. For example, forward-deployed troops from Europe were among the first units deployed in both the Bosnia and Kosovo operations because they had to travel a much shorter distance from home station to the theater than troops based in the continental United States. According to a former commander-in-chief of the European Command, the 1st Armored Division's deployment to Bosnia from its bases in Germany reduced the number of days required for full deployment and cost significantly less than deployment would have by a similarly equipped unit based stateside using strategic airlift and sealift. Also, European-based units deploy to Bosnia and Kosovo primarily by rail and road transportation, and are therefore less costly to move than forces requiring air transportation. War fighting risk is another factor to be considered. If personnel, weapons, and equipment have to be moved to a conflict in Europe or Southwest Asia from the United States, they would take longer or require more airlift capacity than the same units coming from Europe, which would increase risk. For example, the Patriot missile battalion in Europe would need the airlift capacity of 59 C-17 cargo aircraft to move to the area of operations under the Central Command. But the same battalion, coming from the United States, would require twice the airlift capacity to arrive within the same timeframe, according to Defense officials. If that capacity were not available, it would take longer to arrive, which would increase the war fighting risk. Again, the Mobility Requirements Study 2005 modeled the Army forces in Europe as they were planned, at the time of the study, for fiscal year 2005. In written comments on a draft of this report, DOD generally concurred with the information in our report. DOD's comments are reprinted in appendix I. DOD also provided technical comments, which we incorporated as appropriate. To determine the impact of U.S. forward presence in Europe on mobility, we reviewed the Mobility Requirements Study 2005 and other Defense mobility studies. We obtained briefings, reviewed documents, and interviewed officials at the Office of the Secretary of Defense, the Joint Chiefs of Staff, the military services, the Central Command, the European Command, the U.S. Transportation Command, the Special Operations Command, the Joint Forces Command, and the Air Mobility Command. We also obtained information and held discussions with officials at U.S. Army, Europe, and U.S. Air Forces, Europe, headquarters. We conducted our review from May 2001 through August 2001 in accordance with generally accepted government auditing standards. We are sending copies of this report to the appropriate congressional committees, the Honorable Donald H. Rumsfeld, Secretary of Defense, and The Honorable Mitchell E. Daniels, Jr., Director, Office of Management and Budget. Copies will also be made available to others upon request. Please contact me at (757) 552-8100 if you or your staffs have any questions concerning this report. Major contributors to this report are listed in appendix II. In addition to those named above, Lawrence E. Dixon, Patricia Lentini, Alan Goldberg, and Stefano Petrucci made key contributions to this report.

Summary:
The United States maintains 100,000 military personnel in Europe to provide rapid response in the event of a military crisis and help shape the international environment. These forward-deployed forces and equipment also facilitate the movement of U.S. forces to an area of operations. DOD has not quantified the impact of a forward presence in Europe on mobility requirements. However, Defense officials believe that, without forward-deployed forces and equipment in Europe, mobility requirements and costs would be considerably higher and deployment times longer, increasing war-fighting risk. The U.S. en-route system of airbases is critical to operations in Europe and Southwest Asia. U.S. prepositioned weapons and equipment in Europe facilitate military operations in nearby areas. Air Force aircraft and personnel deployed in Europe allow forces to move more quickly to small-scale contingencies in the area and reduce the airlift and sealift burden on U.S.-based units. As with the Air Force, Army combat and support units stationed in Europe allow forces to move more quickly and at less cost to small-scale contingencies in the area.