Case 3. Route ciphers. In this case, whole words of the message are transposed according to some of the methods of Case 1 or 2 or their equivalents. The route cipher is little used at present. Its development and use during the Civil War was caused by the inability of the telegraphers of that day to handle regular cipher matter correctly and rapidly. It was, even in those days, frankly only a delaying cipher and, to be of any value, had to be filled with meaningless words to conceal the message proper. An example from the Signal Book will suffice to show the general character of route ciphers. To one familiar with monoliteral transposition ciphers, even the best of route ciphers offers but little difficulty. "To encipher the message 'MOVE DAYLIGHT. ENEMY APPROACHING FROM NORTH. PRISONERS SAY STRENGTH ONE HUNDRED THOUSAND. MEET HIM AS PLANNED.' arrange as follows: MOVE STRENGTH PLANNED SAY DAYLIGHT ONE AS PRISONERS ENEMY HUNDRED HIM NORTH APPROACHING THOUSAND MEET FROM Here the route is down the first column, up the fourth, down the second and up the third." This cipher was often complicated by the introduction of nulls for every fifth word. Thus the above message might be sent: MOVE STRENGTH PLANNED SAY NEVER DAYLIGHT ONE AS PRISONERS LEAVING ENEMY HUNDRED HIM NORTH UNCHANGED APPROACHING THOUSAND MEET FROM COME. The words in italics are nulls and not a part of the message and the receiver eliminates them before arranging his message in columns to get the sense of it. As an additional complication, it was customary for each correspondent to have a dictionary or code in which the names of all prominent generals and places and many of the prominent verbs,--as to march, to sail, to encamp, to attack, to retreat,--were represented by other words. A route cipher using the code words of the War Department code might have some advantages over the method of enciphering code messages as prescribed in that Code. General Remarks on Transposition Ciphers It is the consensus of opinion of experts that the transposition cipher is not the best one for military purposes. It does not fulfill the first, second, and third of Kerckhoffs' requirements as to indecipherability, safety when apparatus and method fall into the hands of the enemy, and dependability on a readily changeable key word. However, transposition ciphers are often encountered. They are favorites with those who find the substitution ciphers too difficult and too tedious to handle and who believe that their transposition methods are either absolutely indecipherable or sufficiently so for the purpose of concealing the text of a message for the time being. They seem to be particularly popular with secret agents and spies, presumably because special apparatus is rarely necessary in enciphering and deciphering.