Few things are more symbolic of the nautical world than signal flags. Ashore, a man wearing a belt decorated with an array of signal flags may be a yachtsman (or want others to think he is), and a restaurant with signal flags on its menu is likely to specialize in seafood. On the water, signal flags are used more seriously by recreational boaters, working mariners, merchant seamen, and naval sailors the world over.
Using 40 different flags and pennants (singly or in combinations of two or three) that represent the letters of the alphabet (identified by their phonetic alphabet names), along with ten numeral pennants and four specialty pennants, mariners can use the universally accepted International Code of Signals to “talk.” They can tell other mariners such things as “You are running into danger” (the Uniform, or U, flag); “I have a man overboard” (Oscar); “I require medical assistance” (Whiskey); or “I have a doctor on board” (Alfa-Lima).
No one knows for sure when signal flags were first used for naval purposes, but Thucydides refers to Athenian galleys coordinating their maneuvers, and some scholars assume this was accomplished using signal flags. The progenitors of flag signaling first used ensigns to convey nationality and later added the hoisting of a red flag (sometimes referred to as “the bloody flag”) to indicate hostile intent and a white flag to propose a truce.
Over time, other flags appeared, such as personal command flags and specialized pennants. These were gradually adapted for communication purposes by assigning special meanings to their physical placement on different masts or spars. This practice first was standardized in 1673, during the Third Anglo-Dutch War, when a printed volume of “Instructions for The better Ordering His Majesties Fleet in Sayling” [sic] was distributed by the British Duke of York, aka the Lord High Admiral.
Gradually, more flags were created to expand the vocabulary of the signaling commander. Initially, signals were intended as one-way communications, and only the admiral’s “flagship” would carry a full set of the needed flags. Over time, signaling became duplex. All ships carried a full “flag bag,” thereby allowing them to respond or even initiate their own signals.
In the Royal Navy, this system became more complex over time, but it was also quite effective. Just before the Battle of Trafalgar, Vice Admiral Horatio Nelson sent his fleet the famous message “England expects that every man will do his duty” using 33 flags in a coded array.
The first U.S. signal book did not appear until 1797, when Captain Thomas Truxtun devised a system using 10 numeral pennants. In 1861 a whole new system was required for the U.S. Navy when some of the service’s officers resigned their commissions and joined the Confederate Navy, taking their signal books with them. The 1913 edition of The Bluejacket’s Manual was the first to include signal flags.
Today, despite all the advances in electronic communications, signal flags remain in use among most world navies because they have several advantages over their electronic counterparts. The flags are relatively inexpensive, require little maintenance, and are not power dependent. Language barriers among allies can be bridged using translated signal books. Unlike radio signals, which enemies can intercept over long distances, signal flags can convey tactical information among ships within sight of one another without fear of interception. Currently, NATO member nations share the same signal-flag codebook and rely on a flag bag containing the same set of 40 flags and pennants used by merchants and 28 more, for a total of 68.
Perhaps the most engaging use of signal flags is when they are employed for tactical maneuvering. Most of those who have experienced this sight will admit that they feel a rush of excitement and a connection to their seagoing heritage when an array of flags drops smartly from the yardarms of half-a-dozen ships and they all turn together like the finest drill team ashore.
To the uninitiated, this evolution appears almost magical in its execution. It begins when the OTC (officer in tactical command) sends aloft an array of flags, or “hoist,” with a special meaning, such as “Turn together 90 degrees to port”—which can be conveyed using only three flags. This hoist is raised as high as it will go—“close up” or “two-blocked,” in nautical parlance.
The other ships under the OTC’s command will repeat the signal exactly but keep their hoists “at the dip,” about three-quarters of the way up, until the officer of the deck on board each ship grasps the meaning of the signal and indicates that understanding by ordering the repeated hoist to be closed up. When all ships have done so, the OTC executes the signal by hauling down the initial hoist, and all ships will likewise immediately haul down their acknowledging hoists while simultaneously executing the maneuver. All of this is done with alacrity and precision, and the result is seagoing choreography at its finest.
Colorful, cryptic, and eclectic, signal flags have long been a part of nautical tradition and have earned that special accolade from the current Allied signal book, “Bravo Zulu”—Well Done!
Lieutenant Commander Cutler, a former gunner’s mate second class, is the Gordon England Chair of Professional Naval Literature at the U.S. Naval Institute. His many books include numerous editions of The Bluejacket’s Manual (Naval Institute Press), a copy of which every U.S. Navy enlistee receives.