Signal Communications Advanced During the Age of Sail

Coded Flag System, Other Tools Aided Sailors During Maneuver, Combat Situations

By DAVID F. WINKLER

Network-centric warfare has transformed the fleet’s ability to rapidly react and respond to threats against our nation and its armed forces. Using “Chat” and other high-speed modes of digital communications, command centers at sea and ashore are linked, giving all in the command structure a better view of the big picture, helping to dissipate the fog of war.

Dating back to the Barbary Wars and earlier, efficient communication has been essential to naval operations. With the recent bicentennial of the Feb. 16, 1804, raid into Tripoli Harbor by Lt. Stephen Decatur Jr., commanding officer of the schooner Enterprise, to deny the enemy use of the captured frigate Philadelphia by burning her — dubbed “the most bold and daring act of the age” by British Adm. Lord Horatio Nelson — a look at how Decatur and his contemporaries communicated is timely.

Within the Navy Department Library’s Special Collections Rare Book Room are many national treasures, two of which are signal books from the first decade of the 19th century.

Signals to be Used By the Squadron, published in 1807 by Robinson and Little of Brooklyn, N.Y., provides printed text for nearly 500 combat, maneuvering and general administrative situations that could be signaled by numerical flags and colored pennants.

In this book, actions to be taken were listed alphabetically. Under “A,” there are numerous signals discussing “Advance” and “Anchor.” For “B,” there are “Battle” instructions. When the book was delivered to a squadron from Brooklyn, an officer assigned one-to-three digit numeric codes to these actions. For example, the signal “Battle: engage as you come up with the enemy” was assigned No. 82.

As an added measure of “communications security,” the coding officer also inked flags and pennants on the second blank page then assigned the flags numbers. In the 1807 signals book, a white bar over red bar flag meant No. 0, white over green equaled No. 1, yellow over green represented No. 2 and so on up to No. 9.

In contrast, A Code of Signals by David Porter, Commanding Naval Officer New Orleans Station, was created from scratch in 1809. Using exquisite penmanship, its author illustrated 316 signals.

Porter structured his book differently. His opening section contained “Interrogatory Signals” and “Answer to Interrogatory Signals.” It’s easy to imagine that a commanding officer would dread getting the No. 3, “Are you certain you have made no mistake?” signal. Porter then had sections containing “General Sailing and Maneuvering Signals,” “Compass Signals & Signals of Direction,” “Battle Signals,” “Signals for Anchoring and Getting Underway” and “Miscellaneous Signals.”

As with the 1807 book, flags were assigned different numeric values as a measure of communications security. In Porter’s book, No. 1 was a red flag.

The two books also contain night signal sections. The 1807 book discussed the hoisting of lanterns in a wide variety of patterns. The Porter book adds the use of rockets as a signaling tool.

For scholars of the age of sail, Porter’s book provides an added bonus with an explanatory section detailing the meaning of the signals and diagrams of sailing formations. As such it provides invaluable insight into the tactics and sailing formations of the period.

For more about the Special Collections of the Navy Department Library, visit the Naval Historical Center’s website, www.history.navy.mil.

Dr. David F. Winkler is a historian with the Naval Historical Foundation. Navy Department Library Head Librarian Jean Hort assisted with this article.