In the summer of 1863, in the midst of the American Civil War, Confederate General John C. Pemberton was under extreme pressure. A Pennsylvanian who had married a Southern woman and decided to throw in his lot with the seceding states, Pemberton had been placed in charge of what may well have been, at that time, the second most important command (after Robert E. Lee’s army in Virginia) in the entire Confederacy.
Pemberton had been given responsibility for keeping the city of Vicksburg, Mississippi in Confederate hands. Located on a bluff overlooking the Mississippi River, Vicksburg was considered the linchpin holding together the eastern and western halves of the Confederacy. The big guns the Confederates had placed there gave them control of the river. As long as the rebels held onto Vicksburg, they could prevent Union forces from passing up and down that vitally important waterway that President Lincoln called “the Father of Waters.” At the same time, they would be protecting their own ability to send food and war supplies across the river from western states like Texas and Louisiana to the east where they were so badly needed. Both presidents, Abraham Lincoln in the North and Jefferson Davis in the South, considered Vicksburg to be the key to their side winning the war.
But now Vicksburg was under siege. Union General Ulysses S. Grant had fought a brilliant campaign that had defeated Pemberton’s army in several battles before bottling it up in the town. Totally cut off from the outside, and with so little food left in the city that both soldiers and civilians were reduced to eating mules, dogs, cats, and even rats, Pemberton and his army were growing desperate. Over and over Pemberton sent messages to General Joseph Johnston, the overall Confederate commander for that theater of the war, pleading with him to send help.
One of the commanders who was notified of Pemberton’s plight was Major General John G. Walker, whose division was posted on the western side of the river. Walker’s force was just a few miles away from Vicksburg. But not only were they on the wrong side of the river, as far as aiding Pemberton was concerned, they were also in pretty bad shape themselves. About a third of Walker’s men were unfit for duty, due to “excessive heat of the weather, deadly malaria of the swamps, [and] stagnant and unwholesome water.”
That’s the background to the message Walker sent to Pemberton on July 4, 1863. It was entrusted to a courier who was to row across the Mississippi and deliver it to the besieged and desperate general at Vicksburg.
The message, written on a small piece of paper, 6.5 by 2.5 inches, with sewing thread tied around it, was sealed in a medicine vial with a cork stopper. The vial also contained a .38 caliber bullet, undoubtedly included to insure that the bottle would sink if the courier had to throw it into the river to keep it out of enemy hands.
But what that messenger couldn’t keep out of enemy hands was Vicksburg, itself. It was that very same 4th of July that the city and its defenders finally surrendered to General Grant.
When the courier realized he couldn’t deliver his message to General Pemberton, he apparently returned the vial, unopened, to Captain William A. Smith, General Walker’s Assistant Adjutant-General.
For whatever reason, Captain Smith held on to the message bottle for decades after the war. Finally, in 1896, he decided to donate it to the Museum of the Confederacy in Richmond, Virginia. The museum accepted the gift, putting it on exhibit. And there it remained, still unopened, for more than a century.
Eventually, the museum staff got curious about the message in the bottle, and in 2008 decided to find out what it said. They arranged to have the vial carefully opened by a conservator. Finally, the message penned so long ago could be read!
Except, it couldn’t be. The message, containing six lines of text, was in code, and nobody on the museum staff could figure out what it said.
If you want to take a shot at code breaking, here’s the original message:
July 4th (the date was not in code)
SEAN WEIUIUZN: DTG CNP LBNXGK OZ BJQB FEQT FEQT XZBW JJOA
TK HER TPZWK. PBW RYSQU VOWPZYXX QEON EK WASSKIPW PLVO
JKZ HMN NVAEUO XV DWAJ BOYPA SKI MLD TYYROE LVPL.
MFYSIU XY FQEO NPK M OBPC FYXJFHOHT AS ETOV B OCAJOSVQU
M ZTZV TPIY DAW FQTI WTTJ J DQGOAIA FLWHTXTI QMTR
Unable to decipher the message on their own, the museum staff called in retired CIA code breaker David Gaddy, and former Navy cryptologist Commander John Hunter. Working independently, both were able to break the code.
The code breakers discovered that the message was written using what’s called a Vigenère cipher, which uses a key phrase to indicate the offset of each letter from its normal place in the alphabet.
In this case the key phrase was one commonly used by the Confederates, MANCHESTER BLUFF. You would repeatedly write that phrase above the letters of the message, then calculate the real letter using the offset indicated by the corresponding letter of the key.
The offset values were straightforward: “A” was an offset of zero (so, since in the coded message the letter under the “A” in MANCHESTER BLUFF is “E”, the second letter in the decoded message must also be an “E”). B represents an offset of 1, C an offset of 2, etc.
It’s probably just as well that Pemberton, with a starving army and desperate for aid, never received the message — it wasn’t very encouraging. Here’s what the decoded message says:
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 you some caps [a type of explosive device]. I subjoin a despatch from General Johnston.
Pemberton had already realized he would receive no help from General Johnston, who simply didn’t have a large enough army to attack Grant. Now, General Walker, too, was letting Pemberton know he was entirely on his own.
If General Pemberton hadn’t already decided that he couldn’t hold out any longer, receiving General Walker’s message might have been the final straw that pushed him into surrendering Vicksburg to General Grant.