Most people didn't know but in George Washington's time he was a spy. He found ways to use secrets codes, use invisible ink and find ways to decode them. How they used invisible ink, or known as lemon juice is they write in the juice and let it dry and when they sent it you would have to heat the paper to read the message.. Best idea for when there letters could fall into the wrong hands.
Some of the wars this president served in as a commander were...