sailboat signal flags

A sailboat flies its signal flags high: Oscar-Whiskey-Sierra. (Image courtesy Brian Fitzgerald via Flickr)

With history rooted in military maritime battle, Catholic missionary expansion and the European trading of supplies and goods, nautical signal flags are still hoisted to this day. Because you never know when you’ll need to give your neighbor the heads up, “This ship is quarantined.”

The first recorded nautical flag system was used in 1530 by the British military navy as well as the Sovereign Military Order of Malta, a group of Catholic missionaries who acted as early diplomats and travelled by boat. In the days before GPS, satellites and smart phones, imagine spying something far off on the horizon, across great expanses of land and sea. The flag system, especially crucial in times of war, became a clear way of saying, “This is who I am. And these are my intentions.”

Imperative at sea, signal flags needed to be identified from the greatest distance possible, and hence required a very simple design. The classic size and shape we know today was a significant debate among captains: What were the ideal measurements for being able to spot the flag from afar? For example, sparrowheads, a flag with an inset triangular cut-out, fell out of favor because they flopped around too much and were therefore too hard to read. Standard flag proportions (10:19) were determined in 1687 out of necessity: the measurements mirror one yard of bunting.

vintage signal flags

Two flags, many meanings.

Similarly, it was custom to use blue, red, yellow and white for the practical reason that only those dye colors were readily available at the beginning of the 17th-century. In 1730, the French defied British tradition by adding 12 new colors to their 21 naval regiments’ flags – hoisting lavender, light grey and burgundy shades to the confusion of all. The fervor was short-lived, however, since the four primary colors originally picked by the British are still the easiest to spot at a distance – along with black, which was added to the International Maritime Code of Signals.

By the 18th-century, signal flags also developed an alphabet, with each letter getting its own name (R for Romeo, W for Whiskey, etc.)The International Code of Signals only approved the alphabet as code in 1956, when the U.S. Navy started putting it into practice. Individual flags still have specific and standard meanings, as well as retaining their early symbolic meanings. A white square on a blue flag, for example, has long meant, “about to sail” – but it also represents the letter P. And the Alpha flag is raised by diving support vessels to indicate an inability to move from their current location when they have a diver underwater, warning other boats to keep clear. Flags can also spell out a message, letter by letter. One or more flags can form a code word, if both parties are privy to the meaning.

Lord Nelson signal flag message

The message Lord Nelson communicated to his men during the Battle of Trafalgar. (Image courtesy Holywell House Publishing, U.K.)

Adding to the complexity, the simple act of hoisting a flag at the front of a ship rather than the rear can communicate an entirely different message. No wonder many ships had a signal code master aboard, devoted expressly to translating flag language. The most complex of messages were captain’s orders to their own fleet during battle. At the Battle of Trafalgar in 1805, as part of the Napoleonic wars between the French, Spanish and British, Admiral Lord Nelson famously encouraged his army to victory by communicating, “England expects that every man will do his duty.” Not easy to decipher, but the other British ships read his message loud and clear. One can only imagine the signal master’s panic while hoisting these up the mast, careful not to make a mistake, as the French and Spanish ships were firing off their cannons.

Today, this intricate language of possible combinations is about as commonly used as Morse code but as fun as a good game of chess. When crossing international waters, sailors are still cautious about flying their flags to say, “Here I am. I mean no harm.

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  1. Posted June 22, 2015 at 1:27 AM | Permalink

    Despite everything i'm gaining from you, while I'm attempting to achieve my objectives. I completely appreciate perusing all that is posted on your site. Keep the posts nearing. I truly admire each and every thought that you have posted on your site.

  2. Posted May 1, 2017 at 2:05 PM | Permalink

    Thank you for provided in a brief history and explanation of nautical signal flags. My parents both met in the navy and I remember trying them trying to help me memorize these numerous flags when I was a kid. I’m really interested in how flags are used to state who is on the ship and it’s purpose. I think I’ll look into memorizing these different meanings of the flags so that I can impress my parents during summer break.

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