10 U.S.C. § 101(a)(13) (2010) (Title 10—Chapter 1: Definitions)
(a) In general. The following definitions apply in this title:
(13) The term "contingency operation" means a military operation that—
(A) is designated by the Secretary of Defense as an operation in which members of the armed forces are or may become involved in military actions, operations, or hostilities against an enemy of the United States or against an opposing military force; or
(B) results in the call or order to, or retention on, active duty of members of the uniformed services under section 688, 12301(a), 12302, 12304, 12305, or 12406 of this title [10 U.S.C. § 688, 12301(a), 12302, 12304, 12305, or 12406], chapter 15 of this title [10 U.S.C. §§ 331 et seq.], or any other provision of law during a war or during a national emergency declared by the President or Congress.