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. As a result, we could not determine how the study concluded that planned transportation assets were adequate because the study did not contain a transparent analysis to support its conclusion. In our opinion, it is important for decision makers to have an understanding of both combat tasks that must be achieved and the amount of transportation assets needed to achieve those tasks with some level of success. This understanding would allow creation of a clear roadmap for investment decisions. However, we could not determine how the study calculated the specific numbers of transportation assets needed or whether there are specific gaps, overlaps, or excesses in transportation assets, a key objective of the study. Previous DOD mobility studies, including the Mobility Requirements Study--2005, primarily used mobility metrics, which measured success in terms of tons of equipment and personnel moved per day to accomplish military objectives. Million-ton- miles per day is a commonly accepted measure of airlift performance and reflects how much cargo can be delivered over a given distance in a given period of time based on the capability of each type of aircraft. A similar mobility metric--short tons--is used to measure ship capability. However, these studies did not fully integrate combat tasks as a metric. The use of both warfighting and mobility metrics to measure success would allow decision makers to know whether there is sufficient capability to achieve warfighting objectives, as well as to understand the number, type, and mix of mobility assets that are actually needed. In some cases, the MCS results were incomplete, unclear, or contingent on further study, making it difficult to identify findings and evaluate evidence. Relevant research standards require results to be presented in a complete, accurate, and relevant manner; conclusions to be sound and complete; and recommendations to be supported by analyses. Our analysis of the MCS report found that it contains several recommendations for further studies and assessments, five of which are under way. The five studies address intratheater lift capabilities; sealift petroleum, oil, and lubricants; logistics contingency operations capabilities; aerial refueling; and integrated global presence and basing. However, the report does not explain the potential effect of these ongoing studies on the MCS results after the studies are complete, nor does DOD have plans to report the effect of these studies on the MCS results. In addition, the report contains qualified information that is not presented clearly in the report, such as varying assessments of intratheater assets in three different places. For example, the report states in the assessment section of the executive summary that projected transportation assets are sufficient to address intratheater demands in the fiscal years 2007 through 2013 time frame. However, in the recommendations section of the executive summary, the report states that DOD should take action to determine the proper mix of intratheater assets needed to meet requirements. Then, in the part of the report that discusses intratheater airlift, the report states that a detailed analysis of intratheater airlift needs would require improved modeling tools to accurately capture interactions among land, sealift, and airlift capabilities and that data sets must be developed that accurately describe the requirement in light of emerging concepts. VV&A of models and data used to conduct the study was not complete because it was not done in accordance with DOD policy or relevant research standards. DOD policy issued by the Under Secretary of Defense for Acquisition, Technology and Logistics requires that DOD models and data go through a VV&A process. Moreover, relevant research standards state that a study report should include a VV&A accreditation report that is signed by the study director and addresses the models and data certification. DOD officials acknowledged that they did not comply with the VV&A policy when using legacy models in the MCS because they believed such an approach was not warranted for legacy models that have been used for many years and have proved reliable. Moreover, these officials believe that such long-term use constitutes a VV&A process equivalent to that required in the policy. However, the DOD policy does not specify that the actual use of a model constitutes an equivalent VV&A process. VV&A of models and data reduces the risk inherent in the use of models and simulations by improving the credibility of modeling and simulation results. We previously reported our concerns that DOD did not follow its policy in executing the MCS and had little documentation to support the VV&A process used. We found that the final MCS report contained a description of the equivalent VV&A process, but DOD officials could provide no further documentation to verify and validate this equivalent process other than the description included in the report. We also found no documentation in the study report to support DOD claims that the models have proven reliable. Furthermore, DOD officials were unable to provide documentation to support and verify key analytical and decision-making processes used by senior DOD leadership throughout the study. Relevant research standards support documenting the study's analytical and decision-making processes to ensure the accuracy, completeness, and credibility of study results. DOD officials told us that the study's key analytical and decision-making processes were validated and approved by study participants during working group meetings and by senior leadership during General Officer Steering Committee meetings and Executive Committee meetings. PA&E officials could not produce documentation of these meetings because they said documentation did not exist. Nor could they produce other documents we requested during the development of the MCS or following issuance of the report. Consequently, we were unable to determine the adequacy and completeness of the analytical and decision-making processes that supported the MCS effort and that we believe are significant to the credibility of the study and its conclusions. The methodological limitations in the MCS that we identified--some of which were acknowledged by DOD in the MCS report--raise questions about the adequacy and completeness of the study and its report. Until DOD improves aspects of the modeling and data used to conduct the MCS--such as defining its homeland defense mission needs and developing models for the deployment order process--decision makers may not have adequate and complete information about DOD's mobility capabilities to enable them to make fully informed investment decisions. Furthermore, in the absence of an explanation of how identified modeling and data limitations could affect the study results or how such limitations could affect projected mobility capability requirements, the accuracy of the study's finding that projected capabilities are adequate to achieve U.S. objectives with an acceptable level of risk during the period from fiscal years 2007 through 2013 is unclear. Moreover, without a transparent comparison between existing mobility assets and projected needed assets, decision makers will be unable to use study results to identify and quantify the specific types and mix of mobility assets needed to address mobility gaps, overlaps, and excesses. Until DOD conducts an adequate and complete future MCS and clearly discloses all limitations and their effects on the study results, decision makers likely will not have full information concerning DOD's mobility capabilities. As a result, we suggest that Congress and other decision makers exercise caution in using the MCS to make programmatic investment decisions. To provide decision makers with adequate and complete information concerning mobility capabilities so they are able to clearly understand the operational implications of the study and make fully informed programmatic investment decisions, and to improve the usefulness of future mobility capabilities studies, we recommend that the Secretary of Defense take the following three actions, when conducting future mobility capabilities studies beginning with any study currently underway: develop models and data for all critical missions, such as homeland defense, and processes, such as the flexible deterrent options/deployment order process; include in study reports an explanation of how stated limitations might impact the study results and, at a minimum, describe how recommended future studies might be conducted to enhance the results of the original study; and incorporate both mobility and warfighting metrics in determining capabilities. In commenting on a draft of this report, DOD concurred with our first and third recommendations. DOD stated it did not understand our second recommendation that the Secretary of Defense, when conducting future mobility studies, beginning with any study currently underway, include in study reports an explanation of how ongoing and follow-on studies and modeling and data limitations that are referenced in the report could affect the reported results. DOD also noted that it plans to continue its ongoing efforts to enhance the models and data collection processes used to assess mobility capabilities across the full range of strategic missions and supports the notion that continual improvements are needed. As we noted throughout our report, the MCS report contains numerous and repeated references to the need for improved modeling and 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. DOD further commented that while a completed study can recommend that follow-on studies be conducted, it cannot explain how future studies might affect the results of the current study. We acknowledge that DOD cannot quantitatively predict the outcome of an ongoing or future study. However, we believe DOD should be able to explain what ongoing follow-on studies or evaluations seek to determine, what changes are being made to the data inputs and modeling tools that are being used to conduct the studies, and how DOD expects the results may differ from current study results. While the explanation may be hypothetical, as are many operations research study hypotheses, it can provide decision makers with a better understanding of the current study's limitations and results and how an ongoing or future study's results may differ. Therefore, we refined our recommendation to recommend that the Secretary of Defense, when conducting future mobility studies, beginning with any study currently under way, include in study reports an explanation of how stated limitations might impact the study results and, at a minimum, describe how recommended future studies might be conducted to enhance the results of the original study. For example, if modeling and data are limitations to a study, the report should discuss the ways in which the results might change with better models and data. DOD also commented that our report contained misleading information and factual errors and that it stands by the adequacy and completeness of the MCS. The department provided examples in its technical comments where it believed our report contained misleading information and factual errors. We disagree with the department's comments regarding the facts in our report and have addressed each of the department's comments in appendix II. Lastly, DOD stated that the MCS and its conclusions are well accepted by the civilian and military leadership of the department, and pointed out that in March 2006 testimony before the House Armed Services Committee, the Commander, U.S. Transportation Command, stated that the planned strategic airlift fleet determined by the MCS is "about the right capacity". However we note that in the same hearing, the Commander also stated that he thought DOD needed "somewhere in the neighborhood of" 20 C-17 cargo aircraft beyond what is planned. We also note that in the Commander's April 2006 testimony before the Senate Armed Services Committee, Subcommittee on Sealift, he stated that, in an internal Focused Mobility Analysis to study strategic mobility from a Transportation Command perspective, the MCS will be the baseline, "but we will explore how changes in key assumptions may impact the analytical outcome." We are sending copies of this report to the Secretary of Defense; the Director of PA&E; and the Office of the Chairman, Joint Chiefs of Staff. We will also make copies available to others upon request. In addition, the report is available at no charge on the GAO Web site at http://www.gao.gov. If you or your staff have any questions regarding the briefing or this report, please contact me at (202) 512-8365 or solisw@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. GAO staff who made key contributions to this report are listed in appendix III. To conduct our review of the Mobility Capabilities Study (MCS), we reviewed and analyzed the final MCS report; the MCS Terms of Reference; the MCS Study Plan; applicable Department of Defense (DOD) strategic planning guidance; as well as other DOD guidance, directives, instructions, and memos that describe how DOD would conduct its MCS. We also reviewed the National Security Strategy of the United States of America and the National Military Strategy of the United States of America; DOD guidance concerning data collection, development, and management in support of strategic analysis; DOD modeling and simulation instruction; Defense Modeling and Simulation Office guidance; descriptions of models used to conduct the study; and the databases used in the models. We interviewed study officials from the Office of the Secretary of Defense, Program Analysis and Evaluation (PA&E), and the office of the Chairman, Joint Chiefs of Staff, Logistics, as well as study participants and subject matter experts from the U.S. Transportation Command, Air Mobility Command, Surface Deployment and Distribution Command, the combatant commands, and the military services concerning the extent of their input to the study. We also interviewed officials from the Office of the Secretary of Defense, Acquisition, Technology and Logistics, and the Modeling and Simulation Technical Director at the Defense Modeling and Simulation Office. Additionally, we reviewed research literature and DOD guidance and identified frequently occurring, generally accepted research standards that are relevant for defense studies such as the MCS that define a quality or sound and complete study. The following were our sources for these standards: GAO, Government Auditing Standards: 2003 Revision, GAO-03-673G (Washington, D.C.: June 2003); GAO, Designing Evaluations, GAO/PEMD-10.1.4 (Washington, D.C.: GAO, Dimensions of Quality, GAO/QTM-94-1 (Washington, D.C.: February RAND Corporation, RAND Standards for High-Quality Research and Analysis (Santa Monica, Calif.: June 2004); Air Force Office of Aerospace Studies, Analysts Handbook: On Understanding the Nature of Analysis (January 2000); Air Force, Office of Aerospace Studies, Air Force Analysis Handbook, A Guide for Performing Analysis Studies: For Analysis of Alternatives or Functional Solution Analysis (July 2004); Department of Defense, DOD Modeling and Simulation (M&S) Verification, Validation, Accreditation (VV&A), Instruction 5000.61 (Washington, D.C.: May 2003); Department of Defense, Data Collection, Development, and Management in Support of Strategic Analysis, Directive 8260.1 (Washington, D.C.: December 2, 2003); and Department of Defense, Implementation of Data Collection, Development, and Management for Strategic Analyses, Instruction 8260.2 (Washington, D.C.: January 21, 2003). During the process of identifying generally accepted research standards we noted that not all studies are conducted the same way. For example, while all studies use data, not all use baseline data. Likewise, all studies require analyses, but not all use models or simulation to conduct analyses. We tailored the research standards we identified as relevant to the MCS, as shown in table 1. We used these relevant standards as our criteria to assess the reported MCS results. All eight key areas of the study process were considered to have equal importance relative to the soundness and completeness of the study; that is, a sufficiently serious concern in any category could raise questions concerning the adequacy and completeness of the report. The analysts independently reviewed evidence relevant to each subquestion, including the study itself, the study Terms of Reference, and its strategic planning guidance. For each of the subquestions in the key study process areas, the analysts determined whether (1) the evidence had no limitations or raised no concerns, (2) the evidence had some limitations or raised some concerns, (3) the evidence had significant limitations or raised significant concerns, or (4) we could not determine the extent of limitations or concerns because there was not sufficient information. The analysts then met, compared, and discussed their individual assessments, and reached an overall assessment for each subquestion. Areas of the study where we identified either "some" or "significant" limitations or concerns were considered to affect the adequacy or completeness of the study. Additionally, areas of the study that could not be assessed because of the lack of supporting documentation were considered to affect the credibility of the study. Throughout our review PA&E officials told us that the documentation needed to support and verify the key analytical and decision-making processes used to conduct the MCS, documentation that was vetted and approved by DOD leadership and all of the study participants, would not be completed and available for our review until the study report was issued. However, after the report was issued, we were told that the report provides all of the supporting documentation needed and that the other documentation we requested could not be provided. As a result, we were unable to determine the adequacy and completeness of the analytical and decision-making processes that supported the MCS effort to evaluate the credibility of the study. We believe these processes are significant to the credibility of the study and its results. We conducted our review from July 2004 through July 2006 in accordance with generally accepted government auditing standards. 1. DOD disagreed with our assessment that the modeled year--2012--did not place as much demand for mobility assets in support of smaller military operations, such as peacekeeping, as other years. DOD also stated that we incorrectly focused on the number of operations, not the level of effort. We disagree. The MCS report (Annex A to Appendix F) made no distinction between the number of lesser contingencies and the level of effort. Specifically, the Vignettes for Baseline Security Posture Analysis did not report the level of effort by year and instead aggregated the data, in many instances across several modeled years. Consequently, we compared the number of operations conducted in the model year. Throughout our review, PA&E officials consistently told us that the completed MCS report would contain all the documentation needed to support its analyses. Furthermore, although demand in the modeled year may exceed previous efforts, the MCS was chartered to assess the ability of the mobility system to support the National Military Strategy into the next decade. The size of the selected model year in relation to efforts conducted between 1941 and 2006 is not at issue. As our report makes clear, our concern is that modeling what appears to be the least demanding year does not address whether the United States has sufficient capability to support national objectives during a peak demand period and may underestimate and underreport demands to senior decision makers. 2. DOD disagreed with our observation that the MCS report does not provide a clear understanding of the direct relationship of warfighting objectives to transportation capabilities. We disagree. We understand that achieving a combat task requires delivering the right commodity to the right place at the right time. However, the specific combat tasks (e.g., attaining air superiority) necessary to satisfy the commander's campaign objectives are not a direct measure of mobility capability. For example, the problems in using a single metric are reflected in the MCS Appendix H, where the MCS report states that "the study itself still had difficulty in evaluating the operational impact of the delivery of theater support elements," adding that "we were unable to develop a satisfactory mechanism to capture the linkage of the closely related, but delayed, follow-on support needed..." Finally, the MCS concludes that "there was no way to model a decrease in squadron effectiveness if this support was late. Additional effort is required to develop a methodology for evaluation the operational impact of support equipment availability." We continue to believe, and DOD agreed with our recommendation, that warfighting metrics, in conjunction with mobility metrics, can give decision makers a full picture of the capabilities needed to meet a specific warfighting goal. 3. DOD disagreed with our statement that the MCS was unable to model the flexible deterrent options/deployment order process and that the study in fact analyzed flexible deterrent option (FDO) movements to theater. We do not dispute that DOD analyzed FDO movements as part of the MCS analysis. However, the degree to which the MCS analyses successfully modeled FDOs is in question. The MCS report, Appendix H, stated that an individual FDO is essentially the same as a deployment order. It also states in that section that "Deployment orders are issued to deploy specific capabilities as commitment decisions are made. This was not modeled due to lack of data on how DEPORDS would have been issued for an MCO [major combat operation] deployment." In the same paragraph, the MCS concludes that "the impact on the mobility system of the DEPORD process should be assessed in follow-on MCS analyses," adding that "there is a data deficit on how to model and execute a DEPORD process." Furthermore, the MCS report states that "additional analysis is required to investigate the implications of the DEPORD process decisions and provide data for future decision-makers to develop a DEPORD execution process." 4. DOD believes our statement concerning homeland defense missions is misleading and is not sure what the report means by "actual homeland defense demands." We removed the word "actual" and clarified our report to discuss "demands derived from a well defined and approved concept of operations for homeland defense", which were not available for the study according to the MCS report. Furthermore, in chapter 4, the MCS report states that "maintaining a dedicated capability to support multiple, nearly simultaneous homeland defense/civil support events concurrent with the peak demand period of two overlapping warfights, greatly exceeds programmed lift capabilities". This raises questions about the conclusions of the MCS that there are adequate mobility capabilities to meet national security objectives. Also, in Chapter 3 of the MCS report, it states that the DOD homeland defense concept of operations required refinement and was one of nine issue areas cited within the homeland defense portion of the study that "need to be addressed and investigated in more detail." All of these nine areas potentially impact mobility support for homeland defense operations. Moreover, the MCS Executive Summary notes that reassessment of these missions is required as DOD's role in homeland defense evolves. The MCS report, chapter 4, concludes by calling for further refinement of mission requirements, continuing risk assessments, and an effort to determine corresponding mobility solutions. We continue to believe that the MCS conclusion that adequate mobility capability exists is conditional given the results of the homeland defense portion of the study and that the accuracy and completeness of the data, modeling, and results for this portion of the MCS remain in question. 5. We disagree with DOD's characterization that our information was "misleading" regarding the adequacy of some aspects of the MCS' modeling and data. Furthermore, we continue to disagree with DOD's statement that the models and data used by the study were sound and adequate to assess relevant aspects of missions required to support the National Military Strategy, and that the results of the study are valid. In this report, as in our September 14, 2005 report, we reaffirm our concern that the data and models used by the study may not be sound and the results may not be valid since the verification, validation, and accreditation (VV&A) of the models and data used to conduct the study was not done in accordance with DOD policy or relevant research standards. VV&A of models and data reduces the risk inherent in the use of models and simulations by improving the credibility of modeling and simulation results. We do not dispute DOD's assertion that it has relied upon the same models to produce mobility studies done "since the end of the Cold War". However, as we discuss in our report, the MCS report fails to explain or qualify the impact that identified data or modeling limitations might have on its results. For example, in the MCS chapter 4, entitled Operational Data, the MCS states that "data deficiencies negatively affected MCS's ability to use current execution data to project future requirements and assess system performance." Unclear is the extent to which these deficiencies impacted the MCS ability to meet the objective of identifying mobility capability gaps, overlaps, or excesses and provide associated risk assessments, an MCS objective. Similarly, in the section of chapter 4 entitled Analysis Tools, the report states that "MCS analysis revealed several deficiencies in existing mobility models." The section concludes with five recommended tool enhancements but it does not explain the impact that the absence of these enhanced tools may have. We continue to believe that because of these modeling and data limitations, the MCS may have incorrectly estimated the future mobility requirements needed to support homeland defense missions, smaller contingencies, and major combat operations. Ann Borseth, Assistant Director; Brian Lepore, Assistant Director; Nabajyoti Barkakati; Renee Brown; Claudia Dickey; Ron La Due Lake; Oscar Mardis; Deborah Owolabi; Kenneth Patton; and Stephen Woods made significant contributions to this report.

Summary:
The Department of Defense (DOD) issued the Mobility Capabilities Study (MCS), which was intended to identify and quantify the mobility capabilities needed to support U.S. strategic objectives into the next decade. The MCS found that projected capabilities are adequate to achieve U.S. objectives with an acceptable level of risk--that is, current U.S. inventory of aircraft, ships, prepositioned assets, and other capabilities are sufficient, in conjunction with host nation support, and assuming planned investments take place. The Senate report accompanying the bill for the fiscal year 2005 Defense Authorization Act required GAO to report on the adequacy and completeness of the MCS. GAO assessed the extent to which the MCS met generally accepted research standards that this type of study would be expected to meet to be considered sound and complete. DOD used an innovative approach in conducting the study and acknowledged methodological limitations in its report; however, it did not fully disclose how these limitations could affect the MCS conclusions and recommendations. Therefore, it is not transparent how the analyses done for the study support DOD's conclusions. Measured against relevant generally accepted research standards, GAO has identified limitations in the MCS and its report that raise questions about their adequacy and completeness. GAO suggests that Congress and other decision makers exercise caution in using the MCS to make investment decisions. Among GAO's findings: Aspects of modeling and data were inadequate in some areas because data were lacking and the models used could not simulate all relevant aspects of the missions. The report did not explain how these limitations could affect the study results or what the impact on projected mobility capabilities might be. Generally accepted 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. 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 the data used may be incomplete. 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, but the study assumed a robust use of this process. In addition, the MCS report contains over 80 references to the need for improved modeling or data. While the MCS concluded that combined U.S. and host nation transportation assets were adequate, in describing the use of warfighting metrics in its analyses, the report does not provide a clear understanding of the direct relationship of warfighting objectives to transportation capabilities. Additionally, the report stated 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 both warfighting and mobility metrics would allow decision makers to know whether combat tasks were achieved and how much strategic transportation is needed to accomplish those tasks. In some cases, the MCS results were incomplete, unclear, or contingent on further study, making it difficult to identify findings and evaluate evidence. Relevant research standards require results to be presented in a complete, accurate, and relevant manner. For example, the report contains recommendations for further studies and assessments, five of which are under way. However, DOD has no plans to report the impact of these studies on the MCS results after the studies are complete. In addition, the report contains qualified information that is not presented clearly, such as varying assessments of intra-theater assets in three different places.