Military call sign

Military call signs are call signs assigned as unique identifiers to military communications. In wartime, monitoring an adversary's communications can be a valuable form of intelligence. Consistent call signs can aid in this monitoring, so in wartime, military units often employ tactical call signs and sometimes change them at regular intervals. In peacetime, some military stations will use fixed call signs in the international series.

The United States Army uses fixed station call signs which begin with W, such as WAR, used by U.S. Army Headquarters. Tactical call signs are often assigned to a company sized unit or higher. For example, the collective "Checkmate" might be assigned to an entire company and thus "Checkmate Red 6" would be the first platoon leader (platoons are red for first, white for second, blue for third, black for headquarters, and often additional colors for other portions under the command), "Checkmate white 6" to the second platoon leader, etc. "Checkmate 6" is the Company Commander and "Checkmate 6 Romeo" is the commander's radio-telephone operator (Romeo the NATO phonetic of the letter R). Under NATO conventions, 6 is designated the commander or leader, 5 the second-in-command or executive officer, 7 the chief NCO. Also, companies often have the letter they are designated by ('A', 'B', 'C' or 'D') be the first letter of their call sign. This means a 'C' Company could potentially have 'Checkmate' as its call sign.

Fixed call signs for the United States Air Force stations begin with A, such as AIR, used by USAF Headquarters. The USAF also uses semi-fixed identifiers consisting of a name followed by a two or three digit number. The name is assigned to a unit on a semi-permanent basis; they change only when the U.S. Department of Defense goes to DEFCON 3. For example, JAMBO 51 would be assigned to a particular B-52 aircrew of the 5th Bomb Wing, while NODAK 1 would be an F-16 fighter with the North Dakota Air National Guard. Individual military pilots or other flight officers usually adopt a personal aviator call sign.

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