machine. This indicated the initial rotor setting for a message and that setting changed with every message. Discovering a method for rapidly determining the rotor settings became the next task for the cryptanalysts.

At first the mathematicians attempted to solve the problem by using the indicators included in each message. Since the German cipher clerk determined the initial rotor settings, they had to be sent to the intended recipient in the clear, that is, unenciphered. The first three letters of the code group, sent unenciphered, told the receiver where to set the rotors. The following six letters were the ciphered letters (repeated) of the settings for the rest of the message. They were sent twice in order to avoid garbles in transmission. For example, the clerk might send HIT in the clear.