The MCS was the first assessment of DOD’s mobility system since 2000. The study was designed to identify changes in DOD’s transportation force structure due to changes in threats and national security and military strategies. The MCS is the fourth in a series of major mobility studies that DOD has conducted since the end of the Cold War. The first study, the Mobility Requirements Study, conducted in 1992, was undertaken because of concern about the DOD’s strategic mobility capabilities in the wake of Operation Desert Shield and Operation Desert Storm. That study established mobility requirements for the post-Cold War era; defined baseline requirements for intertheater, or strategic, mobility; and proposed a long-range investment plan to meet these requirements. The Mobility Requirements Study Bottom-Up Review Update, conducted in 1994, reaffirmed the need for increases in key mobility components and validated the prior study’s recommendation for the procurement of additional ships for afloat prepositioning and for surge deployments of forces based in the continental United States. The Mobility Requirements Study—2005, issued in 2001, projected future mobility requirements based on two nearly simultaneous major regional contingencies. It included a broader range of factors, including host nation support and enemy use of weapons of mass destruction, than the previous studies. The current MCS, which began in May 2004, reassessed DOD’s mobility capabilities against the backdrop of a revised National Military Strategy that included the ongoing war against violent extremism, an evolving global defense posture, a new force-sizing construct, revised campaign scenarios, and ongoing departmentwide transformation efforts. The study results were intended to support decisions on future strategic airlift, aerial refueling aircraft, and sealift procurements needed to meet varying military requirements. The study used an innovative “capabilities-based” approach, measuring existing and currently projected mobility capabilities against warfighting demands that could be expected in fiscal year 2012 while also considering mobility demands during the 7-year period from fiscal year 2007 through fiscal year 2013. According to DOD officials, the Secretary of Defense believed this approach would give him greater flexibility in deciding which capabilities to fund in a constrained budget environment. In considering each aspect of the National Military Strategy, the MCS modeled warfighting scenarios in the year 2012 using different premises with varying assumptions to develop and evaluate mobility capability mix alternatives. The models were used to evaluate transportation alternatives, including variations in alternative transportation modes (air, land, sea) and sources (military, civilian, foreign), as well as factors that affect transportation mode and source decisions. The scope of the MCS described the study as an assessment of the full range of transportation needs required to support (1) combat operations; (2) smaller military efforts, such as peacekeeping or overseas evacuation of American citizens; (3) homeland defense/civil support, such as disaster relief and antiterrorism response; and (4) other strategic missions, such as strategic nuclear and global strike missions. The study was coauthored by the Office of the Secretary of Defense, Office of the Director, Program Analysis and Evaluation (PA&E), and the Chairman, Joint Chiefs of Staff, Office of the Director of Logistics. Other DOD components involved in the study included the U.S. Transportation Command and its subordinate commands, the Office of the Under Secretary of Defense (Acquisition, Technology and Logistics), the combatant commanders, the military services, and others. The final report was signed on December 19, 2005, by the Deputy Secretary of Defense. As measured against relevant generally accepted research standards, limitations in the MCS study and report raise questions about their adequacy and completeness. For example, aspects of modeling and data were inadequate in some areas because data were lacking and some of the models used could not simulate all relevant aspects of the missions. Furthermore, the exclusive use of warfighting metrics in the MCS analyses limited the usefulness of the report. Moreover, in some cases the MCS results were incomplete, unclear, or contingent on further study, making it difficult to identify findings and evaluate evidence. Finally, verification, validation, and accreditation of models and data used to conduct the study were incomplete because they were not done in accordance with DOD policy or relevant research standards, and supporting documentation for key processes could not be provided. Aspects of modeling and data were inadequate in some areas because data were lacking and some of the models used could not simulate all relevant aspects of the missions. Relevant research standards require that models used are adequate for the intended purpose, represent a complete range of conditions, and that data used are properly generated and complete. As DOD acknowledged in the MCS report as a study limitation, some modeling tools were not available to analyze key missions. The MCS cited deficiencies in several existing mobility models and the need for follow-on MCS analyses. The MCS report also acknowledged that the identified deficiencies in data hindered analysis of future requirements and transportation system performance. However, the report did not explain how these limitations could affect the study results or what the effect on the projected mobility capabilities might be. For example, the MCS modeled hypothetical homeland defense missions rather than homeland defense demands derived from a well defined and approved concept of operations for homeland defense, because the specific details of the missions were still being determined, and DOD acknowledged that the data used are incomplete. The MCS report recommended further analysis of mobility capabilities after homeland defense needs are refined. However, the report did not identify the potential effect that using these hypothetical scenarios might have on the MCS results. The MCS also was unable to model the flexible deterrent options/deployment order process to move units and equipment into theater because of lack of data on how deployment orders have been issued in the past for major combat operations. However, the MCS assumed a robust use of the flexible deterrent option/deployment order process, which in one scenario accounted for approximately 60 percent of the early airlift movement prior to the beginning of combat operations. Instead, the MCS modeled the flow of forces and equipment contained in the time-phased force deployment data process. Based on the scenarios provided for the MCS analyses, we could not determine how the deployment order process would affect the mobility assets required for major combat operations. The MCS report noted that additional analysis is required to determine the implications of the deployment order process and to provide sufficient information for decision makers concerning the amount of future mobility assets actually needed. In addition to these modeling and data issues, the MCS report contains more than 80 references to the need for improved modeling, and 12 of these references call for additional data or other refinements, such as follow-on analyses, further assessments, future evaluations, additional study, and investigation of alternatives in a wide range of areas, such as antiterrorism response, infrastructure availability, intratheater airlift, strategic sealift, air refueling, and availability of civil reserve aircraft. Some of these studies are currently underway, as discussed later in this report. Moreover, our analysis of the MCS report showed that the year modeled (2012) to determine the DOD transportation capabilities needed for the years 2007 through 2013 did not place as much demand for mobility assets in support of smaller military operations, such as peacekeeping, as other years. To establish transportation demands for mission requirements, DOD developed and used a baseline security posture that covered a 7-year period. This baseline was developed, in part, using a historical analysis of DOD’s movement of personnel, equipment, supplies, and other items. According to DOD officials, Office of the Under Secretary of Defense for Policy, which developed the baseline security posture, selected the year modeled in the MCS because it was deemed the “most likely” to occur in terms of transportation demands and because it was not statistically different from other years in the 7-year period. However, our analysis showed that 2012 involved the least demand for transportation assets in support of smaller military efforts than any year in the 7-year period and did not fully stress the defense transportation system. Figure 1 depicts the number of hypothetical ongoing contingencies for each year in the baseline as shown in the MCS. Although not transparent in the study, DOD officials said scenarios in the year modeled were not intended to fully stress the defense transportation system. DOD officials provided no further explanation for the year selected to develop the DOD transportation capabilities other than it was directed by Office of the Under Secretary of Defense for Policy and agreed to by the study leadership. We believe that selection of a different year that placed an increased demand on transportation assets for smaller military efforts may have revealed gaps in mobility requirements. Therefore, we found that the selection of 2012 as the modeling year was a limitation in the MCS with respect to smaller military efforts. Because of these modeling and data limitations, the MCS may have incorrectly estimated the future mobility requirements needed to support homeland defense missions, major combat operations, and smaller contingencies. Until DOD improves aspects of the modeling and data used to conduct the MCS—to include defining its homeland defense mission needs, developing models for the deployment order process, and explaining how identified modeling and data limitations could affect the study results—decision makers may not have adequate and complete information about DOD’s mobility capabilities. While the MCS concluded that combined U.S. and host nation transportation assets were adequate to meet U.S. objectives with acceptable risk, the report, in describing the use of warfighting metrics in its analyses, does not provide a clear understanding of the direct relationship of warfighting objectives to transportation capabilities. The report acknowledged that further analysis is required to understand the operational impact of increased or decreased strategic lift on achieving warfighting objectives. Relevant generally accepted research standards require that conclusions be supported by analyses. The use of warfighting metrics is a measure to determine whether combat tasks, such as establishing air superiority, are achieved. However, they do not measure success in terms of whether appropriate personnel, supplies, and equipment arrived in accordance with timelines.