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The Joint Army/Navy Phonetic Alphabet was a radio alphabet developed in 1941 and was used by all branches of the United States military until the promulgation of the ICAO spelling alphabet (Alfa, Bravo) in 1956, which replaced it. Before the Joint Army/Navy (JAN) phonetic alphabet, each branch of the armed forces used its own radio alphabet, leading to difficulties in interbranch communication.
Vestiges of the system remain in use in the U.S. Navy, in the form of Material Conditions of Readiness, used in damage control. Dog, William, X-Ray, Yoke, and Zebra all reference designations of fittings, hatches, or doors. The response "Roger" for "· – ·" or "R", to mean "received", also derives from this alphabet.