Official definition of the United States Department of Defense military term "hostile act ".
1. A hostile act is an attack or other use of force by any civilian, paramilitary, or military force or terrorist(s) (with or without national designation) against the United States, US forces and, in certain circumstances, US nationals, their property, US commercial assets, or other designated non-US forces, foreign nationals, and their property. 2. Force used directly to preclude or impede the mission and/or duties of US forces, including the recovery of US personnel and vital US Government property. When a hostile act is in progress the right exists to use proportional force, including armed force, in self-defense by all necessary means available to deter or neutralize the potential attacker or, if necessary, to destroy the threat.