Educator's Guide: Mathematics: Code Breakers


Communications is vital to any military operations, but even more important is keeping the message from the prying eyes and ears of the enemy. In order to confuse the enemy, ingenious codes and ciphers were developed. These encrypted messages could be sent by signal flags or telegraph. Once the message was encoded, even if it was intercepted, it would have little value to the enemy - unless of course, he broke the code. One type of cipher system was a disk. The cipher disk allowed soldiers to encode signal flag messages. The numbers on the outer ring were flag movements that represented letters on the inner ring. By turning the rings to a prearranged setting, signalmen could change the code at will. Major Albert J. Myer, commander of the U.S. Army Signal Corps, believed the cipher disk so sensitive, he urged his men to die rather than allow the disks to fall into Confederate hands.


Divide your class into teams of 3 or 4. Have each team put together the cipher disk and write a military message they will encode. One of the challenges decoders faced were geographic names. A misspelled name could affect critical information on troop movements and sizes. Pair up teams, one will send the message the other will receive. Give each team pair a starting point on the cipher disk, example team pair 1: a = o, team pair 2: a = 9 etc... Each team pair will send and decode their message, the remaining teams will try to decipher the message. Older students can be challenged by not have the cipher disk to aid in the decoding. Computer students can develop a game for writing and decoding messages

Classroom Activities:

  • Computer
  • Language Arts
  • Mathematics
  • Social Studies


  • 4- 12


Students will use a binary coding system to write, translate and analyze messages


  • Cipher disks, brass paper clasp, paper and pencils. A variation on this activity would be using signal flags. Have the students make signal flags. The flags were white with red square, diamond etc... or red with white square, diamond etc... Have the students send their messages with the flags. one = up, to the right, to the left and back two = down, to the right and up This will help students understand how difficult it was to send and receive signals. Adding to the scenario were sharpshooters who targeted I signalmen. Other cipher and code activities can be found in Social Studies or Odds 'n' Ends.

Cipher Disk:

Last updated: April 14, 2015

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