DOD relies on a cadre of program managers to lead the development, delivery, and sustainment of individual weapon systems throughout their life cycles. The program managers are the designated individuals with responsibility for and authority to accomplish the program’s development, production, and sustainment objectives to meet the users’ operational needs. Additionally, along with certain other senior officials, the program manager is responsible for decision-making and program execution and is accountable for results. Program offices include the program managers and other individuals who support the program. Product teams, comprised of program office staff and other relevant experts and contractor officials, as appropriate, also support the management of the program. Generally, program managers or their designees interact with prime contractors who manage subcontractors to provide the final good or service to DOD. In addition, program executive officers within the military departments manage a portfolio of programs (e.g., aircraft, missiles, combat vehicles, and ships). Once delivered to DOD, weapon systems are sustained under various arrangements that may include contactors, DOD organic facilities, or some combination of the two. Materiel support commands in the military services, as well as the Defense Logistics Agency, manage inventories of spare parts, and individual weapon system programs are typically supported by a complex supplier network that includes a prime contractor, sub-contractors, and various tiers of parts suppliers. Within the Office of the Under Secretary of Defense for Acquisition, Technology and Logistics, the Office of the Deputy Assistant Secretary of Defense for Supply Chain Integration describes its mission as establishing strategic supply chain governance and reporting and overseeing the integration of global logistics and supply chain performance. According to the office, its specific responsibilities include leading the development of DOD supply chain policies, reducing excess inventories, improving control of critical assets, and strengthening detection of counterfeit items, among others. Also within the Office of the Under Secretary of Defense for Acquisition, Technology and Logistics, the Deputy Assistant Secretary of Defense for Manufacturing and Industrial Base Policy (MIBP) is responsible for various industrial base matters, including developing DOD policy and providing guidance, oversight, and technical assistance on assessing or investing in defense industrial capabilities to the Under Secretary of Defense for Acquisition, Technology and Logistics. MIBP supports the Office of the Secretary of Defense and Service Acquisition Executives by providing analyses of defense supply chains and recommendations for taking appropriate actions to maintain the health, integrity, and technical superiority of those supply chains. MIBP reports annually to the Senate and House Armed Services Committees on DOD’s industrial base assessments, actions initiated during the previous year to better understand or respond to risks, and investments planned for certain defense industrial base funding programs. MIBP’s assessments of the supply base are intended in part to identify and mitigate weaknesses stemming from fragile suppliers that are likely to be disrupted or from critical characteristics that make a part difficult to replace. MIBP typically analyzes supply base issues that jointly affect more than one DOD component. The military services also conduct supply base analyses that focus on their own programs. DOD recognizes that there are potential risks to its supply chain, including risks associated with having single sources of supply, and DOD’s policy is to identify and manage these risks. Specifically, DOD Instruction 4140.01 states that potential disruptions in the DOD supply chain shall be identified, monitored, and assessed to mitigate risk to supply chain operations. The instruction further indicates that supply chain risk management strategies shall be employed to address potential supply chain disruptions. Some examples of supply chain disruptions are unreliable suppliers, flooding, terrorism, labor strikes, and natural disasters. While DOD has multiple sources of supply for some parts, it relies on a single source for many others. There are a number of reasons for using single sources of supply. For example, demand for parts may not be high enough to justify the cost of maintaining more than one production line, and limitations on DOD’s access to technical data may also inhibit its ability to develop multiple sources of supply. DOD has established a process for analyzing defense infrastructure called the Critical Asset Identification Process (CAIP). CAIP is intended to provide a common analytical framework that is consistent and repeatable to identify critical assets, such as facilities to protect against supply disruptions. This process is part of DOD’s Mission Assurance program, which is intended to protect and ensure the continued functioning of capabilities and assets by securing, protecting, and managing the risks of programs that support DOD’s mission. The defense industrial base is one of several defense infrastructure sectors, and CAIP is repeated annually to identify critical facilities, or “assets,” in the defense industrial base that must be protected. As the Defense Infrastructure Sector Lead Agent for the defense industrial base, the Defense Contract Management Agency (DCMA) leads this process for the defense industrial base, working in conjunction with MIBP. According to DOD, defense industrial base input into CAIP is supported by a continuous assessment process that includes fragility and criticality assessments, service industrial base assessments, data calls to the services and defense agencies, and direct information from industry. According to its October 2016 report, in implementing the CAIP, DCMA evaluates assets in the defense industrial base against risk-based criteria. One of the key criteria it notes is whether an item has a single source of supply. From an initial list of important capabilities, the annual process results in three main lists of assets—task assets, task critical assets (TCA), and defense critical assets; each successive list is of more critical importance to DOD and national security. DOD officials stated that the assets on these lists remain relatively stable from year to year. Figure 1 shows how DOD describes different types of assets and the criteria for each type of asset list within CAIP. When the annual CAIP is completed, the TCA list for the defense industrial base (as well as assets from other defense infrastructure sectors) is submitted to the Joint Staff, which then is responsible for compiling DOD’s overall TCA list from across all defense sectors. From this list, Joint Staff officials also nominate assets for consideration as defense critical assets and provide them to the Assistant Secretary of Defense for Homeland Defense and Global Security for approval. Defense critical assets are the most critical type of asset, defined as assets of such extraordinary importance to operations in peace, crisis, and war that incapacitation or destruction would have a very serious, debilitating effect on the ability of DOD to fulfill its missions. DOD’s October 2016 report on single source of supply risks fully addressed two elements of the direction in the Senate Report, partially addressed one element, and did not address one element. Table 1 summarizes our assessment of DOD’s report against each element. DOD’s report contained two classified appendixes, one that identified a list of more than 380 task assets and the other that identified a list of 33 TCAs. Based on our analysis of these appendixes, we found that the information they contained addressed two elements of the Senate Report’s direction, identifying (1) major defense acquisition programs with operational implications and (2) a list of critical components of such programs that are provided by a single source of supply. The list of task assets includes information about each facility, such as the major defense acquisition programs that are supported by that facility and the part or parts it supplies. In many cases, a single facility on the list provides parts for numerous programs. While information on specific programs and parts is not included on the TCA list, it is possible through cross-referencing to identify the information that corresponds to that facility in the task asset list. MIBP officials stated that when the Senate Report direction for a report on single source of supply risks was received, they believed the task would be difficult, as there was no one list of all single sources of supply. However, they determined that the existing CAIP could be used, because it relies on criteria that include whether a facility is a single source of supply. They therefore used information resulting from this process to develop the two appendixes. They noted that the decision to use CAIP to respond to the direction in the Senate Report was discussed with and approved by the Joint Industrial Base Working Group. The working group is a DOD forum to exchange information and collaborate on tasks relative to defense industrial base issues. Its membership includes representatives from the military departments’ acquisition and industrial base assessment organizations. DOD’s report partially addressed the direction to identify risk mitigation actions—with associated implementation plans and time lines—that it would take to prevent negative operational impact in the event of the loss of single-source or single-provider suppliers. The report provided an overview of some of the risk mitigation strategies DOD can use to manage risks resulting from single sources of supply within the industrial base; however, DOD did not identify implementation plans and time lines for any risk mitigation actions pertaining to specific assets listed in the report, including the TCAs. The report listed four tools that DOD can use to mitigate risk in the defense industrial base—Titles I and III of the Defense Production Act, the Manufacturing Technology program, and the Industrial Base Analysis and Sustainment program. Through these available tools, DOD can provide funding to address critical problems within a supply chain or to seek technological innovations as solutions to those problems. DOD’s report did not describe other risk mitigation actions that, according to DOD and service officials, are routinely used by program offices to respond to and mitigate risks, such as life-of-need buys, development of a new source, or redesign of parts, among others. DOD officials have taken steps to mitigate risks or supply issues when they become aware of a loss or a pending loss of a single source of supply. We found that some of the parts supplied by the 33 TCAs have been the focus of funding projects associated with the Defense Production Act, the Manufacturing Technology program, or the Industrial Base Analysis and Sustainment program.