Dead Confederates, A Civil War Era Blog

The Museum of the Confederacy recently announced the discovery of a coded message enclosed in a tiny bottle that’s been sitting, unopened, in the museum’s collection for over a century. The decoded text of the message reads:

Gen’l Pemberton: You can expect no help from this side of the river. Let Gen’l Johnston know, if possible, when you can attack the same point on the enemy’s lines. Inform me also and I will endeavor to make a diversion. I have sent some caps [i.e., percussion caps]. I subjoin a despatch from General Johnston.

The message is dated July 4, 1863, the same day that Pemberton surrendered Vicksburg to General Grant. Pemberton never got the message, and it would not have mattered if he had.

The message is unsigned, but the author, who clearly was unaware of Pemberton’s true situation in Vicksburg, may have been Major General John George Walker (l.), at that time commanding a division in the Confederacy’s Trans-Mississippi Department, and operating in western Louisiana. The message was encoded using the “Vigenère cipher,” in which the letters of the original message are shifted so many spaces over, so that A becomes M, B becomes N, and so forth, based on a key word or phrase known to both the sender and the recipient. Although ciphers of this type had a reputation of being unbreakable, most of the Confederate messages sent in this way that were intercepted by the Federals were quickly decoded. The fact that most Confederate messages used one of only three key phrases, “Manchester Bluff,” “Complete Victory,” and “Come Retribution,” made them more vulnerable than they should have been. (After tinkering with this Vigenère cipher generator, it seems this message used “Manchester Bluff” as its key, at least for the first few words.) As so often with cryptanalysis throughout history, the key to breaking a code often comes from mistakes on the part of the sender.

The message was decoded and its contented confirmed by a retired CIA cryptanalist, David Gaddy, and an active-duty U.S. Navy intelligence officer, Cmdr. John B. Hunter.

______________________

Image: This Jan. 14, 2009 image shows a Civil War bottle with a message that was tucked inside at the Museum of the Confederacy in Richmond, Va. The message to Lt. Gen. John C. Pemberton says reinforcements will not be arriving. The encrypted dispatch was dated July 4, 1863 — the date of Pemberton’s surrender to Union forces led by Ulysses S. Grant in what historians say was a turning point in the war. (AP Photo/Museum of the Confederacy)