The principal officer (the ambassador) in charge of a diplomatic facility of the United States, including any individual assigned to be temporarily in charge of such a facility. The chief of mission is the personal representative of the President to the country of accreditation. The chief of mission is responsible for the direction, coordination, and supervision of all US Government executive branch employees in that country (except those under the command of a US area military commander). The security of the diplomatic post is the chief of mission’s direct responsibility. Also called COM.