The National Imagery and Mapping Agency states, "The purpose of the International Code of Signals is to provide ways and means of communication in situations related essentially to safety of navigation and persons, especially when language difficulties arise."
Before the International Code of Signals, there were a variety of naval signals and private signals prior to 1857. The International Code of Signals started out as the Commercial code, drafted in 1855 by the British Board of Trade and published in 1857. The code was put to the test during WWI and it was found that it failed more often than it succeeded. Between WWI and 1969, there were many efforts to update and improve the system. It was pared down to highlight navigation and safety needs, including medical necessities.
These US Navy signal flags are used primarily to communicate while maintaining a degree of radio silence. When communicating with any vessels, besides naval, the International Code of Signals is used. The code/answer pennant precedes all signals in international code. The signaling flags can be purchased as a complete set, or bought separately.
If you have any questions regarding signal flags, call us at 1-800-858-8776 Monday-Friday, 8:30-5:00 ET or contact us by email.