Some codes turn letters into numbers, like the one George used.  An example of a code like this is one where wind is 679 and wood is 688.  There's an alphabet, too.  You switch the first and third letters, the second and the fourth letters and so on.

    Silas Deane was a great American patriot.  He developed an invisible ink, which people used during wartimes such as the time of the Revolutionary War.  This ink was activated by heat. The ink was used on leaves or pamphlets so that the enemy didn't know there was even a message.  If they didn't see a code, they couldn't break the code.              

    Paul Revere helped lead the Patriots into battle.  He called the Patriots out of bed because the British were attacking.  Paul had asked his friend to let him know how the British were coming.  His friend was told to hang lanterns in the tower of the old North Church in Boston.  One lantern meant that the British were coming by land, and two lanterns meant they were attacking by sea.  This was a code between Paul and his friend.  He rode down the countryside, alerting everyone about the attack.  The familiar saying, “one if by land, and two if by sea,” comes from this event in history. 

            People used other codes and ciphers, also.  The Caesar encryption was used in the Revolutionary War.  Another code used numbers like 38, which meant “attack,” and 129 stood for fort.  This code also had an alphabet.  The letters a through z were replaced with 1 through 26.  This system was called the French Prose.  One bad thing about these types of codes was that you had to have the decoder with you for the message to make any sense.