In recent years, congressional attention has been drawn to the roles and responsibilities of U.S. ambassadors who serve as Chiefs of Mission in U.S. embassies abroad. The death of Ambassador Christopher Stevens in Benghazi, Libya, in September 2012 highlighted the dangers that ambassadors may encounter as the front-line face of U.S. diplomacy, and the availability of resources, leadership, and communication relative to those dangers. The ongoing debate on interagency reform for missions abroad stresses the need to improve coordination among all U.S. agencies, a key responsibility of U.S. ambassadors. The State Department and United States Agency for International Development (USAID) 2010 Quadrennial Diplomacy and Development Review (QDDR) emphasized the need to equip ambassadors to better perform that role. In addition to these specific concerns, congressional interest stems from Congress's part in selecting U.S. ambassadors (as the U.S. Senate advises and consents on their appointment), providing the resources they need to accomplish their missions, and overseeing their conduct of those missions. This report addresses the role and effectiveness of U.S. ambassadors and others who serve as a Chief of Mission (COM) abroad, particularly their responsibility for coordinating interagency activities and their control over U.S. forces operating in their countries of assignment. After a background section on the history of COM roles and a section on the sources of COM legal authority, this report addresses four commonly asked questions regarding the scope and exercise of COM authority. It concludes with a discussion of two prominent congressional concerns: (1) how effective is COM authority in practice? and (2) how might the exercise of COM authority be improved? It will be updated as warranted. "Chief of Mission," or COM, is the title conferred on the principal officer in charge of each U.S. diplomatic mission to a foreign country, foreign territory, or international organization. Usually the term refers to the U.S. ambassadors who lead U.S. embassies abroad, but the term also is used for ambassadors who head other official U.S. missions and to other diplomatic personnel who may step in when no ambassador is present. The U.S. Constitution authorizes the President to appoint ambassadors with the advice and consent of the Senate, that is to say, subject to Senate confirmation. In circumstances where no presidentially appointed ambassador is currently serving at a U.S. mission abroad, legislation further authorizes the President to appoint a career U.S. foreign service officer as a chargé d'affaires or "otherwise as the head of a mission ... for such period as the public interest may require." An ambassador or other foreign service official may hold the COM position within a given U.S. mission abroad. Appointed by the President, each COM serves as the President's personal representative, leading diplomatic efforts for a particular mission or in the country of assignment under the general supervision of the Secretary of State and with the support of the regional assistant secretary of state. The role of the COM has expanded considerably since World War II. With the postwar expansion of U.S. foreign assistance around the world, COMs assigned to head U.S. embassies or other country-based diplomatic missions abroad have been charged with responsibility for overseeing nearly all U.S. government activities in their country of assignment, with the primary exception of military operations. Most often, they exercise this authority through their leadership of the embassy's "country team," the membership of which includes the chief representative of each U.S. government agency undertaking activities in a host country or other mission. The State Department/USAID 2010 Quadrennial Diplomacy and Development Review (QDDR) casts ambassadors as chief executive officers or "CEOs" of multi-agency missions, not only conducting traditional diplomacy, but also leading and overseeing civilians from multiple federal agencies in other work. The QDDR highlights the key role of country teams and ambassadors in the conduct of foreign policy and assistance, and sets forth ways in which the Obama Administration would try to improve the knowledge and skills of COMs and their ability to lead country teams. Civilian agencies "possess some of the world's leading expertise on issues increasingly central to our diplomacy and development work," the QDDR states. "The United States benefits when government agencies can combine their expertise overseas as part of an integrated country strategy," when "implemented under Chief of Mission authority, and when those agencies build lasting working relationships with their foreign counterparts." At the time of the QDDR's release, then-Secretary of State Clinton also announced that Chiefs of Mission were to play a role in integrating country-level strategic plans and budgets. The authorities and responsibilities of COMs are explained primarily in the Foreign Service Act of 1980, as amended (FSA 1980; P.L. 96-465 ). (This legislation also explains the responsibility of all U.S. government officials operating under a U.S. mission abroad to report to the COM and abide by COM directives.) Section 207 of FSA 1980 serves as a codification in legislation of many of the provisions in previous executive orders setting out and developing COM authority as U.S. government activities abroad increased throughout the latter half of the 20 th century. COM authority is also shaped by executive branch directives, which include executive orders and other presidential directives and State Department regulations, some of which provide more extensive authority than FSA 1980. According to State Department regulations, COM authority derives originally from the President's general constitutional powers in foreign affairs. Because of this constitutional basis for COM authority, according to the State Department, the President's letter of instruction (see " Letter of Instruction ," below) providing greater detail to COMs is of greater significance in determining a COM's authority than the pertinent legislative provisions relating to such authority. Section 207 of the FSA 1980 (22 U.S.C. §3927) sets out the three main components of COM authority: (1) the COM's responsibilities, (2) the COM's authority over the personnel stationed at the embassy and in the country of assignment, and (3) the obligations of U.S. government personnel and agencies to that COM. Each component is outlined below. COM Responsibilities . Section 207(a)(1) of FSA 1980 states that, under the direction of the President, a COM "shall have full responsibility for the direction, coordination, and supervision of all Government executive branch employees in that country," except for Voice of America (VOA) correspondents on official assignment and employees under the command of a U.S. Geographic Combatant Commander (GCC). (Recent Presidential Letters of Instruction exclude personnel on the staff of an international organization, but do not reference VOA correspondents, see below.) Pursuant to Section 207(a)(2), the COM is also responsible for keeping " fully and currently informed with respect to all activities and operations of the Government within that country, and shall insure that all Government executive branch employees in that country (except for Voice of America correspondents on official assignment and employees under the command of a United States area military commander) comply fully with all applicable directives of the chief of mission." A principal duty of each U.S. Chief of Mission in a foreign country, under Section 207(c) is "the promotion of United States goods and services for export to such country." COM Authority o ver Personnel . Section 207(b) of FSA 1980 states that any executive branch agency with employees in a foreign country "shall insure that all of its employees in that country" (except for VOA correspondents on official assignment and those under the command of a GCC) "comply fully with all applicable directives" of the COM. Obligation to Keep COM Fully Informed. Subsection (b) also provides that any executive branch agency with employees in a foreign country "shall keep the chief of mission to that country fully and currently informed with respect to all activities and operations of its employees in that country…." Section 207 of FSA 1980 limits COM authority to coordinate and supervise U.S. government activities in a host country to executive branch agencies. In general, representatives of the judicial and legislative branches, including Members of Congress and their staffs, are not subject to the same coordinating and supervisory authorities of the COM. In addition to and in accordance with the relevant legislative mandates, COM authority derives from an array of executive branch orders and directives, explained below. Presidents provide their primary directives in a Letter of Instruction to each COM, setting out each COM's role and responsibilities as the President's personal representative at each U.S. mission abroad. Although the State Department stresses the distinction between the constitutional and legislative sources of COM authority, the Letter of Instruction and Section 207 of FSA 1980 contain similar language on the central points of COM authority. They do not contradict each other in their explanation of responsibilities of the COM and the obligations of other U.S. agency representatives to adhere to the COM's directives in each host country. One difference with the FSA 1980 is the personnel excluded from COM authority. The FSA 1980 excludes VOA correspondents on assignment and personnel under the command of a GCC, as mentioned above. The template of an Obama Administration Letter of Instruction excludes personnel on the staff of an international organization. Another difference is that Letters of Instruction (as indicated by templates of presidential Letters of Instruction of two administrations) state that ambassadors have the right to see "all communications to and from Mission elements," except those exempted by law or executive decision. Executive orders have gradually expanded the authority and responsibilities of COMs. The requirement that COMs coordinate all U.S. government activities in a host country and be kept informed of all activities by U.S. government personnel dates back at least to the early years after World War II, when concerns surfaced about the management of U.S. humanitarian and security assistance to various Western European countries.