The Vigenère cipher is simple enough to be a field cipher if it is used in conjunction with cipher disks. [5] The Confederate States of America, for example, used a brass cipher disk to implement the Vigenère cipher during the American Civil War. The Confederacy's messages were far from secret and the Union regularly cracked their messages. Throughout the war, the Confederate leadership primarily relied upon three key phrases, "Manchester Bluff", "Complete Victory" and, as the war came to a close, "Come Retribution".[6]Claude Shannon, the father of information theory, came up with what was known as the "unity index", the amount of information that must be transmitted using a cipher to unambiguously decode it. The longer a message, or the more information transmitted and intercepted using a single key, the easier it will take to decode. The fact that snippet is brief and that the decoders were possibly unaware of the limited number of keys employed may explain why it took weeks to decode.
An elaboration of the Vigenère cipher is the running key cipher in which the code phrase is taken to be a book or a long passage. The problem with running key ciphers is that the key is available to the enemy and may be compromised. In addition, even if the key is chosen to be in a different language, eventually the non-uniform and non-random relationship among letters in human language reveal themselves and the cryptanalyst eventually can recover both the cipher message and the key. (There is an hilarious instance of this in the book, "The Good Soldier Schweik", in which the cadet decodes the general's "unbreakable" cipher, using an example from a cadet handbook.)
The ulitmate development of the Vigenère cipher is the one time pad, which is unbreakable in principle. A drawback to the one time pad is that the key is as long as the message and the keys must be distributed prior to the communication. The Venona intercepts used "sometime" pads, one time pads that had been reused. The Russians (like most countries at that time) used one time pads that were printed in book form and distributed to there stations worldwide. During the war, apparently some key books were created by reprinting and shuffling pages of previous code books and hoping no one noticed. The Americans noticed.
"The Code Book" by Simon Singh
It's a very interesting book that outlines the history of cryptography and cryptanalysis. The Vigenere cipher is one of the ciphers that is thoroughly discussed. I found a copy at the local library, though I'm sure that there is an electronic copy online somewhere.