What is the central idea in this passage?
 O Invisible ink was a good choice when writing in
 code.
 O Giving up information could be a disaster for either
 side.
 Citish and the Americans frequently used
 riders to carry messages, and both sides tried
 the riders and get the messages. The rider who
 Washington's important messages was
 himself. It happened when Tallmadge and
 s men were attacked by British troops near the
 ut-New York border. Tallmadge escaped
 but lost a saddlebag full of secret papers.
 allmadge's code did not fall into British hands.
 g the papers was a letter from Washington in
 carelessly gave the name and address of an
 corge Higday, saying that he was a man who
 obably "convey intelligence to me." Higday was
 but he had managed to destroy all evidence of
 George Washington could have done a better job
 managing his spies.
 The British used horseback riders to deliver
 messages.
 -George Washington, Spymaster,
 Thomas B. Allen