Flag signals can mean any of various methods of using flags or pennants to send signals. Flags may have individual significance as signals, or two or more flags may be manipulated so that their relative positions convey symbols. Flag signals allowed communication at a distance before the invention of radio and are still used especially in connection with ships.
Flaghoist signalling is one or more flags (or pennants) simultaneously flying from a fixed halyard, and generally any method of signaling by such means. Each of the flags has a distinct shape and color combination. Each flag or combination of flags has a preassigned meaning or "code". The International Code of Signals defines a standard set of flags and associated alphabet suitable for international use, as well as a set of standard codes. Flaghoist is also used in boat racing, to warn of impending severe weather, and other specialized applications.
Maritime flag signalling has a long history, especially prior to the advent of radio, and remains the preferred means of signaling in many situations. In naval flag signalling, additional flags and an expanded list of signals are used for identification and commands, as well as the mercantile uses. Many navies have their own proprietary or secret codes, and use additional flags. A designator flag is used to indicate if a flaghoist signal is meant to be interpreted as an ICS signal or as a naval signal. The U.S. Navy uses a set of 68 flags, including flags for each letter of the alphabet and each numeral to convey messages of tactical or administrative nature.[better source needed]
Flag semaphore signalling uses two flags, held in specific positions to signify letters. This method requires simple equipment but can be obscured by bad weather. A permanently installed chain of semaphore stations is a semaphore line and before the invention of the electric telegraph, was the fastest means of communication over moderately long distances. [better source needed]
In the 1850s, U.S. Army Major Albert J. Myer, a surgeon by training, developed a system using left or right movements of a flag (or torch or lantern at night). Myer's system used a single flag, waved back and forth in a binary code conceptually similar to the Morse code of dots and dashes. This is sometimes called the wig-wag method of signaling, or "wig-wagging". More mobile than previous means of optical telegraphy, as it only required one flag, this code was used extensively by Signal Corps troops on both sides in the American Civil War. (Its first use in battle was by Confederate Lieutenant Edward Porter Alexander at the First Battle of Bull Run in 1861. In this code, alphabet letters were equated with three positions of a single flag, disk, or light. The flags measured two, four, or six feet (60, 120 or 180 cm) square and were generally either red or black banners with white square centers or white banners with red square centers. The disks were 12 to 18 inches (30 to 46 cm) in diameter and were made of metal or wood frames with canvas surfaces. Somewhat easier to handle than the flags, they provided a different method for daylight communications. The lights were kerosene lanterns attached to a staff. A second "foot torch" was placed on the ground before the signalman as a fixed point of reference, making it easier for the recipient to follow the lantern's movements.
Myer's code was ternary (three symbols). However, only two of these symbols were used for letters, making it largely binary. The third symbol only appeared in control characters. Each character consisted of a combination of three basic motions (elements). The neutral position was the flagman holding his device vertically and motionless above his head. The first motion was initiated by bringing the device downward on the signalman's right side and then quickly returning it to its upright position. The second motion brought the device down on the left side and then returned it to the starting position. The third motion lowered the device in front of the signalman, then restored it to its vertical position. Like Morse code, but unlike Myer's original code, this binary code did not have a fixed length for each character. For instance, i was coded as "2", but d was coded as "222". Myer's 1866 manual also includes a 3-element fixed length code using four elements, and the 1872 manual has a 3-element fixed length code using three elements. There is little sign that these codes were widely used. The 1872 manual includes a variable length code using four elements which Myer says was used by the Army, but is superseded.
Myer developed his code based on the telegraph code of Alexander Bain, although the codepoints finally used were not the same as Bain's. The Bain code, invented 1843, was used on the chemical printing telegraph of that inventor and was a dot-dash code similar to the Morse code. Myer came across it while working as a telegraph operator, work he did for a period after his graduation in 1847. In 1851, Myer produced A New Sign Language for Deaf Mutes as the thesis for his medical doctorate. In this publication Myer used the Bain code as the basis for communication with a deaf person by tapping a hand or cheek. Alternatively, tapping a table with which the person was also in contact could be used to pass messages. In 1854, Myer joined the army as an assistant surgeon and was posted to Texas. It was in Texas that he developed the idea of the wig-wag flag or torch code for military use, building on his previous work with the deaf.
In 1856, while stationed at Fort Duncan, Texas, Myer wrote to Jefferson Davis, then Secretary of War, proposing his signalling system. He was supported by Joseph Gilbert Totten the Army Chief of Engineers but failed to get a hearing due to lack of detail in his proposal. In 1857, Totten tried again with a new Secretary of War, John B. Floyd. In 1859, a board of examination under Robert E. Lee considered the proposal but thought it had only limited use. They did not put it into operation but allowed Myer to continue with tests. Myer conducted these tests starting in April, initially at Fort Monroe, Virginia, and later in New York and Washington.
Myer, with Floyd's support, proposed that a new post of signal officer to the Army staff should be created, with him filling it. In February 1860, Myer got a hearing before the Senate Committee on Military Affairs under the chairmanship of Jefferson Davis which supported the introduction of the sytem. Davis opposed the creation of the signal officer post when it came before congress; he wanted to use the signalling system but feared the creation of the signal officer post would lead to the creation of a new department (the future Signal Corps). Davis's objections were ignored and Myer was made signal officer and promoted to major in June 1860.
The first live use of the system was in 1860 in a campaign agaimst the Navajo in the Department of New Mexico. Myer's served under Major Edward Canby who became a strong supporter of the formation of a signal corps, which he thought more efficient than Myer's proposal to train every officer. The Navajo war was over by February 1861, but at the same time the American Civil War was beginning. Up to this point, Myer had been temporarily assigned men from the units in which he served to work as signallers, often grudgingly. This was impractical for a large scale war and Myer now pressed for Canby's idea of a dedicated signal corps. Many in Washington opposed the idea, and it took until 3 March 1863 before the corp was formally inaugurated, although the signallers had been informally called "signal corps" for some time. Myer was put in charge with the rank of Colonel.