act of war
Defined in 1 dictionary — U.S. Code
United States Code
18 U.S.C. § 2331 — as used in this chapter (3 versions over time)
the term "act of war" means any act occurring in the course of—
(A) declared war;
(B) armed conflict, whether or not war has been declared, between two or more nations; or
(C) armed conflict between military forces of any origin;