Alert

State of readiness for a specific action. A warning signal of a natural or
dreaded danger, such as an air attack [Балабін, Гардера, p. 295].
In military science, any method is used to detect the situation or intention of an enemy so that warning can be given.
Because military tactics from time immemorial have stressed the value of surprise—through timing, location of attack, route, and weight and character of arms—defenders have sought to construct warning systems to cope with all these tactics. Many types of warning systems exist. Long-term, or political, warning systems employ diplomatic, political, technological, and economic indicators to forecast hostilities. The defender may react by strengthening defenses, negotiating treaties or concessions, or taking other actions. Equivocal and incapable of disclosing an attacker’s intention, political warning often results in an unevaluated and neglected situation [Encyclopedia Britannica Online].

Sources:

Davis, H. (2019, March 18). Warning system. Encyclopedia Britannica Online. Retrieved from: https://www.britannica.com/technology/warning-system

Балабін, В., Гардера, Р. (2007) Українсько-французько-англійський міжвидовий словник з тактики та логістики. Dictionnaire interamées de termes tactiques et logistiques ukrainien-français-anglais: (в 2-х т.). Київ: нац. ун-т ім. Тараса Шевченка, Військовий