"Una fuerza de caballeria enemiga procedente de Aranjuez y Villaseca se halla en Azucaica. Marche usted con su compania partiendo de la casa de la serradero por las alturas de lo este y norte de Azucaica con el fin de reconocer su numero y clase de fuerzas y en disposicion que se halla. (Q) Esta acantonada (Q) Se hallan otras tropas detras de ella (Q). El resultado del reconocimiento necesito saberlo dentro de tres horas y media cuando mas. Pongo a sus ordenes un ciclista (X) Fin." Special Solution for Case 7 When a short message is enciphered with a long key word, the methods of analysis already discussed may fail; first, because there will be no recurring pairs to indicate the number of alphabets used and, second, because there will be so few letters in each alphabet that the methods of Case 6 will not be easily applied. However, if we know or correctly assume one word, preferably a fairly long one, in the cipher text, a solution is very simple. For example, the following message is believed to refer to reënforcements and to contain that word. YANZV ZNLPP KQFXI JBPWA NRUQP EPLOM CCWHM I Let us assume that REINFORCEMENTS is the first word and that it is represented by the cipher group YANZVZNLPPKQFX. We may put the test in this tabular form, using a cipher disk and a Larrabee cipher card to determine the value of A for each letter under these two systems. Any other alphabets suspected may be tried out at the same time. If Y A N Z V Z N L P P K Q F X equals R E I N F O R C E M E N T S then, with cipher disk, A equals P E R M A N E N T B O D Y P and, in Vigenere cipher, A equals H W F M Q L W J L D G D M F It is evident that the guess as to the appearance of the word REINFORCEMENTS was correct, that it is the first word of the message, that the cipher disk was used in preparing the cipher and that the key words are PERMANENT BODY. This is, of course, an especially favorable case and we will take one less favorable to show how this method can be applied. Two Mexican chieftains, A and B, have been communicating with the following cipher alphabet: Plain text ABCDEFGHIJLMNOPQRSTUVXYZ Cipher PCJVRQZBAODFSUTMXIYHLGEN This alphabet has been determined from many radio messages from A, the superior, to B, his sub-ordinate, who has a force of about 2,000 men near the border. A uses the form ORDENO QUE instead of the more familiar MANDO QUE in all his messages giving orders to B. The following message is received from A by B's radio station (and other listening stations) and about an hour later there is a good deal of noise and movement as if B's force were breaking camp.