Maritime Signal Flag History

The designs of the individual flags are lost in the mists of time. They were developed separately for various iterations of naval and merchant marine signal codes over the course of the 18th and early 19th centuries. What Popham, Marryat, and the Board of Trade did was to assign these mostly pre-existing designs to specific numbers and letters. In other words, a blue flag with a white square on the center was the signal for "about to sail" long before it was assigned to the letter P, and solid yellow was used for purposes connected with quarantine long before it was designated as Q, but whoever designed the first blue flag with a white square on the center is probably not the same person who came up with a yellow flag with a black disk (now used for the letter I).
Joe McMillan, 20 March 2006

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I don't think it is possible to assign credit for the design of signal flags to an individual or nation. One of the earliest maritime entities to make use of a numeral flag signal code was the Order of the Knights of Malta. The galley captains of the Order apparently used codes consisting of up to fifteen flags. I have seen no depictions, but according to the written descriptions, they were of simple single, bicolour and tricolour designs, including pennants of equally simple designs. Simple signal flag design is an imperative at sea and it is the practical seamanlike requirement to be able to identify signal flags at the longest possible distance, which enforced these simple designs. Kempefeldt, Popham, Marryat et al no doubt designed some flags as the codes grew in complexity requiring more flags, but they also made use of many designs already in existence since late medieval or early Renaissance times. Their main claims to fame rest with the code systems they developed and which gradually grew into the modern International Code of Signals. So lets lift a glass or two to the unknown sailors who invented these simple designs still in use today!
Andries Burgers, 20 March 2006

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The expansion of the signal codes in the 18th Century required the invention of a number of hitherto unknown flags and if the compilers of the various codes (or members of their staff as appropriate) did not invent them, then who did? As just one example, the code used by Rodney in 1782 required the addition of 23 previously unknown flags and pennants, and a number of these were later found to be impractical (from a visibility point of view) so had to be revised in subsequent expansions.

The current International Code of Signals contains 40 different flags and pennants and the current NATO code a further 28, whereas a signal book of 1762 shows 26 in total of which only 20 are purely signal flags.

The other six flags were - the (royal) standard, the union jack, the red ensign, and the plain red, white and blue admiral's command flags.
Christopher Southworth, 20 March 2006

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Here are some observations on the subject from an article entitled "The Development of Signalling in the Royal Navy" by Captain (later Vice-Admiral) L.E. Holland [hnd53], published posthumously in the Mariner's Mirror of February 1953.

"Chequered flags should be abolished. Quartered, halved, three-striped, striped corner ways, half up and down, and pierced, are the only ones that are properly distinguished at a distance." Captain Young, Admiral Rodney's flag-captain, 1780.

Kempenfelt thought that three stripe flags were more distinct if the stripes were vertical rather than horizontal, and that chequered pendants were unsatisfactory.

Sir Home Popham wrote in 1812, that the Dutch and French flags were very good over long distances. He also liked the French signal flags which were white with a blue border and red centre, or red border and blue centre.

Swallow-tailed pennants were a shape favoured by Sir Samuel Hood who wrote to Popham in 1814, "The Broad Pendants give great relief to the observer, the flag wafting out with every change of view, the colours are more perfectly distinguished. There certainly is not that advantage in triangular flags; they are in general difficult to discern." However five that were in the 1816 signal book were replaced by different shapes in the 1827 book, and earlier Kempenfelt had written that pendants should not have swallow tails.

Holland wrote that the best colour combinations were red and white, blue/black and white, and blue/black and yellow. Howe considered red and blue a poor combination, and preferred red and black, and yet red and blue is now used in the International Code. Similarly Kempenfelt thought that red and yellow gave poor results and changed this combination for blue and yellow, and yet this is also in the International Code. Perhaps with modern dyes it is possible produce colours that have more contrast than was achievable in the 18th century.
David Prothero, 21 March 2006

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In beginning of 17th century, Mahé de la Bourdonnais use only 4 colours: large blue, scarlet red, arsenic yellow and white.

The maritime world is very conservative because now only one other colour is used extra in International Code of Signals: it is the black. The first man ( to my knowledge) who used black is Lord Richard Howe for his substitute flag. But it is not a proof that manufacturer at the time did not made flags with other colours: for distinguish the 121 regiments of the French ground army in 1730, they used 16 colours: white, blue, blue Turkish, red, carmine, black, green, brown, yellow, dead leaf, dawn, light fawn, isabelle, purple, flax-grey and moiré.
Dominique Cureau, 22 March 2006

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Roland-Michel Barin marquess of la Galissonniere (1693-1756) left the port of Toulon for the expedition of Mahon in the Isle de Minorque on April 8th, 1756 with a fleet of 193 boats carrying an army consisted of 23 battalions with a regiment and a train of artillery. The army was commanded by Mr. the marshal of Richelieu.

The book of signals which used by de la Galissonniere showa the care brought by this leader of squadron to stay in communication with his ships. A reproduction is in Histoire de la Marine by "l'Illustration" 1934. The document is in the National library, Department Manuscripts
Dominique Cureau, 26 March 2006