Ships at sea and even in harbor need to talk to one another. The first method of communication was yelling between two ships. As we all know this is only so effective and can lead to mistakes. People soon learned to use signals to communicate over distances. How ever this too has draw backs. Once the ships drew far enough apart it was impossible to see the signaler.

So to combat this flags were used to send communicate. At first different countries used different flags for different signals. England would hoist a blue flag for one signal and France might use a green flag for the same signal. This could be very confusing for merchant ships that traveled between different countries. The first true international system was written in 1855. Before this time signal breaking was the first code breaking.

Signal flags consist of a different flag for each letter and number. Combining these flags in different combinations sends a signal. For example while in port or underway when a Navy ship is taking on fuel thy fly a single red flag. This is the B or Bravo flag. It tells everyone what the ship is doing. The flag was originally used by the Royal Navy when handling powder.

When ships are closer together signal operators will hold flags in each hand and communicate using semaphore. This is a series of movements with the hands of the signal operator. The movements are each letters and they are transcribed by a second person. The message can be in code or it can be in plain language. A similar system is also done using a light. The light has louvers over the lens. The louvers are opened and closed to send out blips of light. The message is sent using mores code.

Radio transmission allowed ships and fleets to increase the range at which they could travel for one another. During the visual communication days ships might need to stay within a mile or two of one another. With radio transmission the ships could spread out to 15-20 miles apart. With today’s communication systems ships hundreds of miles away can communicate with ease.

During the 17th-19th century the flag ship would be responsible for battle orders. These would be relayed to the other ships in the battle. Those ships too far to see the flag ship would read the signal off the other ships in the group. This could cause problems with a message being relayed incorrectly.