Last modified: 2026-07-25 by olivier touzeau
Keywords: signal flags |
Links: FOTW homepage |
search |
disclaimer and copyright |
write us |
mirrors
See also:
Source: translated from troisponts.net
Naval tactics and the transmission of orders are two closely linked fields, especially in a navy where the aforementioned mindset prevailed. This is aptly illustrated, for example, by the full title of Bigot de Morogue's major work, Tactique navale, ou traité des évolutions et des signaux (Naval Tactics, or Treatise on Evolutions and Signals).
Indeed, it is essential that in combat, each command correspond to a clear signal, easily read and correctly interpreted so that it can be executed quickly.
Since time immemorial, communication at sea has been achieved by means of flags during the day, light signals at night, and the sound of cannon fire in foggy weather. As for daytime signals, the system used until the mid-18th century consisted of assigning specific meanings to flags placed in conventional positions on the masts. This system, convenient for those giving orders, was much less so for those receiving them, as there was no logic to the arrangement and choice of flags: it was necessary to leaf through the entire thick "Book of Orders and Signals," distributed at the start of the cruise, to identify the command to be executed [It was still a system of this type that Bigot de Morogue advocated in 1763]. To remedy this difficulty, some ship commanders had to prepare handwritten booklets in which the signals were arranged according to each of the flags and their placement on the admiral's mast.
Around the middle of the Seven Years' War, an attempt was made to improve the system by introducing "chapters" announced by special flags at the masthead [The "chapter" flags were the only ones to bear a cross, which made them easily recognizable], which indicated which section (Anchorage, Hunting, Combat, etc.) contained the meaning of the hoisted flag of orders.
But these methods of using flags remained very rigid: once at sea, the meaning of a flag could not be changed, which could be a source of indiscretion if the code were to become known to the enemy. Furthermore, some conventional flag arrangements could be difficult to see. This is why several French officers devised improvements.
Bourdé de Villehuet system
The most ingenious was proposed (unsuccessfully) by Bourdé de Villehuet in his Manoeuvrier (1765) [Bourdé attributes the initiative for this system to Mahé de La Bourdonnais, but we have found no trace of him in the archives]: his system was based on the use of ten pennants, numbered from zero to nine, which could be hoisted in the most visible place on the rigging (rather than in a fixed position). It was possible to use one, two, or three of these pennants. A numerical dictionary corresponded to each pennant, giving the meaning of each number associated with the pennants seen. The code's discretion was easily ensured: it was sufficient to change the numerical assignment of each flag, which could easily be done at sea.
Unfortunately, Bourdé was not an officer of the "senior corps" [He was an officer of the East India Company] and, in 1775, the French navy preferred to adopt a system devised by one of its own, the lieutenant commander of the Flag Service. This highly sophisticated system relied on the use of square tables, derived from the "chapters" of the previous code, each divided into cells identified by numbers on the x and y axes. This system offered several advantages of the numerical code proposed by Bourdé (notably the elimination of the need for a conventional arrangement of flags on the mast), but it was very cumbersome to receive, especially when switching from 10 x 10 charts to 13 x 13, and then 16 x 16 charts.
Nevertheless, this numerical system provided the French with a certain tactical advantage during the American Revolutionary War. However, the British, who were still using a traditional system, quickly recognized the advantages of numerical codes and began using the Bourdé system [The chapter devoted to signaling in Bourdé's work had been translated into English by Admiral Kemperfelt as early as 1779] towards the end of the American Revolutionary War.
Despite the improvements made to them, these communication systems suffered from a serious flaw: each signal code was designed for the specific campaign of a particular squadron. One can therefore imagine the problem posed, for example, by the joining of two naval forces using different codes and, sometimes, different systems [The situation arose during the Seven Years' War: thus, in 1759, D'Aché's squadron, which used a "classical" code, was reinforced in India by Froger de l'Eguille's detachment, which had a "chapter" code."].
It was not until 1786 that the French navy introduced a single system and code for all its squadrons. The discretion of this code was ensured by the introduction of numerical correspondences for the flags, which could easily be changed if necessary."
Images:
Corentin Chamboredon, 3 February 2026