It was Gregson who spoke next.
“We have intercepted another message in the new code. This is the first for over a month. The German Second Army is based in Jülich, a garrison town thirty miles west of Cologne and its general is called von Bülow. To the north of him is General von Kluck with the German First Army. We have assumed that, as in the Franco-Prussian war of 1870, any German invasion of France would come from somewhere on the line between the Luxembourg border and the sea.”
“That is a very long front,” observed Holmes drily.
“And I fear,” said the Prime Minister, “the message which Gregson has intercepted, only makes the matter more difficult.”
“Indeed so, gentlemen.” He pulled out of his pocket the three previous messages and the new one which he laid next to each other. “This new message,” he added, “was sent from the German chancellor, Theodor von Bethmann-Hollweg, to General von Bülow.”
Holmes sat with the messages for some time, but when he raised his head, he looked no happier than he had when he had looked at the previous three messages. I set out the new message and the other three below:
“641, 697, 972, 359, 938, 331, 331, 688, 262, 383, 318, 397”
“952, 395, 239, 523”
“311, 697, 164, 197”
“316, 497, 313, 327, 839, 723, 839, 753, 583, 193, 88X”
“I note,” said Holmes at last, “that we have another duplication of a character-set within one message. This new message makes successive use of the set 331.”
“That is so,” said Gregson. “Yet if the sets refer to letters, then there are only two repetitions in thirty-one character-sets. On the other hand, if the characters in the code are functioning as pictograms, we have no idea what places, people or things they refer to. And a solution where the character sets represent words makes even less sense when one of the only two sets that is produced more than once repeats itself consecutively.”
We sat in silence for some minutes before Gregson asked that a map of Western Europe be brought before us.
“I thought I remembered,” said he, “a town’s name that repeats the same word. Look down here—on the map is a German town called Baden-Baden. Could the repeated 331s refer to that?”
“Baden-Baden,” said Holmes, pointing at the map with the stem of his pipe, “is a spa town in the Black Forest. As you can see, it is well to the southeast of the French-Belgian border and then where the Luxembourg-French border meets the German-French border. You can imagine the sophistication of this code if the Germans have made the number 331 represent the word Baden.”
“And that is miles from where the French have disposed their main forces,” exclaimed Grey. “Baden-Baden is twenty-five miles east of Strasbourg, and the French have no significant forces in the area to meet a major advance from there.”
We sat in silent thought.
“And yet I cannot believe that a message in this new and rarely used code is about anything other than troop dispositions,” said Asquith at last. He paused before continuing. “But all our intelligence,” he added at last, “tells us that the Germans, if they advance, will do so from well to the north as the southern part of the French German border down to Switzerland is heavily fortified and the Massif Centrale behind it is terrain that is hard for troops to advance in. Could this be a feint from the south to get us to move troops down there? Or an encircling movement from the south to link up with troops who advance from the north.”
Holmes shrugged, “I cannot advise you on this matter, Prime Minister. You must make the decision on whether to say anything to the French. It would be a grave decision indeed to move forces away from northern France based on a highly speculative reading of two character-sets of a code we have thus far had no success at all in breaking. And the more people you tell about these messages, the greater the chances of the Germans finding out about our ability to intercept their most secret messages even though we have not broken their code.”
The meeting broke up shortly afterwards but not before Asquith had made the following statement which he was to repeat at a speech at the Guildhall in November of 1914. “We will not unsheathe the sword lightly. But if we do so, we shall not lay it down until France is adequately secured against the menace of aggression, until the rights of the smaller nationalities of Europe are placed upon an unassailable foundation, and until the military domination of Prussia is wholly and finally destroyed.”
As we left, I could see Asquith and Grey utterly bowed by the responsibility with which they were faced.
Holmes again came to stay the night. I knew better than to press a confidence, but it was Holmes who initiated the exchange that followed.
“’Pon my word, Watson. It is good to have you before me. I have had to work solo for two years, adopt the beard that you see, and put on an accent the like of which you will never have heard.”
“Perhaps you might elaborate as far as you are able.”
“I first attracted attention in Chicago, graduated in an Irish secret society at Buffalo, gave serious trouble to the constabulary at Skibbareen, and so eventually caught the eye of a subordinate agent of the head of espionage at the German embassy, Count von Bork. Since then I have been honoured by his confidence, which has not prevented most of his plans going subtly wrong, and five of his best agents being in prison. I watched them, Watson, and I picked them as they ripened.”
“You have, I am sure, done the country great service.”
“There is more to come—which is why I am unable to dedicate the time I would like to this code.”
“I would be happy to help you in any way that I can.”
Holmes sat in silence. He had emptied and recharged his pipe before he spoke again in a hushed tone.
“I have a mission tomorrow. My master provides me with a driver to whom I am most forthcoming about what I claim to do. Perhaps, given the number of my master’s spies who have already landed in prison, it would not create suspicion if the one he provides me with were arrested, and I hired one of my own. In this hour of our country’s need, good Watson, I would rather have you at my side than anyone else.”
My regular readers will recognise what happened next, but I summarise what happened for those who do not.
I drove Holmes, disguised as the reprobate agent, Altamont, to von Bork’s house on the coast of the German Ocean (or the North Sea as we are gradually coming to call it). It would have excited too much comment had I, a stranger to the German spy-master, come into the house, but Holmes soon came down to the car to say that he had chloroformed von Bork, and to ask if I would like to join him for a glass of wine.
We sat sipping some quite exceptional imperial Tokay while von Bork lay tied up beside us.
Holmes told me how he had taunted his handler about the arrest of German spies and how von Bork had shown him his safe with the password August1914.
“It is full of documents revealing who the traitors are in our ranks, good Watson. It is the result of three years’ work.”
I looked around the great hall of von Bork’s stately home. “It is certainly a splendid house,” I commented.
“It reminds me rather of Baskerville Hall. Particularly this lofty chamber. You remember the paintings of Baskerville’s ancestors. Henry Baskerville felt that they were watching him. He is of the German nobility, and he has pictures of his ancestors here which he was going to pack up tomorrow to take with him. You can see the likeness of these figures of the past to our prisoner,” Holmes waved in the direction of von Bork, “in spite of all the trappings of wigs, hats, and beards…”
Holmes’s voice broke off.
“Of course, the trappings…” he gasped.
“What do you mean?” I asked.
“I have the appearance of the messages before my eyes, Watson, but I do not have them with me. I never carry anything
with me when on mission for von Bork which could betray what I really am.”
“But what has their appearance to do with it? The coded messages were all in transcript.”
“Let us waste not an instant in taking the comatose von Bork to Scotland Yard where he can be locked away, and then go to see Gregson.”
My readers who know His Last Bow may have been surprised at the jocular tone Holmes adopted on that car journey from Harwich to London. As stated previously, this implausible section was inserted at the request of the British government—“If the public is enjoying your banter,” said Mr Asquith, “they will not think about what else might have been going on.”
In fact, we drove at a break-neck speed to London with Holmes alternating between urging me to drive faster and lamenting, “How could I be so blind, how could I be so blind?”
Once von Bork was safely in the care of His Majesty’s constabulary, Holmes and I dashed round to Gregson’s office in Gower Street. “Even though it is late on a Sunday,” said Holmes, “I am sure that Gregson will be at his desk.”
My friend’s sense was as unerring as ever. Apart from the security guards, Gregson was the only person in the building. He sat in an office lined with maps, dictionaries in different languages, and books on mathematical theory. He visibly brightened when he saw us.
“We have another message, Mr Holmes. Here it is:
‘265, 388, 392, 353, 889, 753, 311, 697, 164, 197, 163, 383, 166, 464, 392, 353, 888, 316, 646, 483, 166, 464’
It was sent late yesterday from Berlin to General von Bülow at Jülich which suggests that he is the key figure in any invasion plans the Germans may have.”
“Give me the other messages,” said Holmes.
“Here they are:
‘952, 395, 239, 523’
‘311, 697, 164, 197’
‘316, 497, 313, 327, 839, 723, 839, 753, 583, 193, 88X’
‘641, 697, 972, 359, 938, 331, 331, 688, 262, 383, 318, 397’
“We could not,” said Holmes, “account for why the messages had so few characters and why none of them repeated. But that was only because we were distracted by the commas between the sets of numbers. Let us see what happens if we put the commas between every two numbers rather than every three.”
Holmes sat down with a pen and a piece of paper and, after, a few minutes came up with the following:
“95, 23, 95, 23, 95, 23
“31, 16, 97, 16, 41, 97
“31, 64, 97, 31, 33, 27, 83, 97, 23, 83, 97, 53, 58, 31, 93, 88X
“64, 16, 97, 97, 23, 59, 93, 83, 31, 33, 16, 88, 26, 23, 83, 31, 83, 97
“26, 53, 88, 39, 23, 53, 88, 97, 53, 31, 16, 97, 16, 41, 97, 16, 33, 83, 16, 64, 64, 39, 23, 53, 88, 83, 16, 64, 64, 83, 16, 64, 64”
Holmes let his breath out with a hiss.
“Well, at least we can see a pattern now. The third message is indeed about Altamont and we can see that 31 is A and that 97 is T.”
“But that means the second message is A_ T_ _ T?” responded Gregson. “I can think of no word that conforms to that pattern in German—and the words in English with a spelling consistent with that are “Artist’ and “Aptest” which are clearly irrelevant to our purposes. In French—a language often used in German military circles, I can...”
At that moment the floor to Gregson’s office flew open and in strode the Prime Minister.
“The Germans have taken over Luxembourg,” he said. “It is good to see you here Mr Holmes and you too Dr Watson. Thank you for your arrest of von Bork, but I assume you are here to crack this code, and this latest turn of events makes the matter imperative.”
“I have cracked the letters of the name Altamont, but it will take me time to break the rest.”
“We have no time, Mr Holmes. I have told the French about the new code. They were also aware of it, but they too have been unable to crack it. We must know whether the main thrust will come with an encircling movement to link up with the Germans’ feint into Luxembourg.”
“Encirclement!” exclaimed Holmes. “That’s it.”
“It’s the standard way of launching a mil..”
“Gregson,” said Holmes, cutting directly across what the Prime Minister was saying, “Gregson, do any of your books on mathematical theory cover pi—the expression of the relationship between the diameter of a circle and its circumference?”
After some searching, Gregson found an expression of pi to a hundred places.
“Look,” cried Holmes! “Pi starts with 3.1 and A is 31. Humans, when they devise numbers for a substitution code, always show a bias towards particular numbers. Using pi as the source of numbers eliminates that.”
He went to a desk and drew up the table which I set out below:
A — 31
B — 41
C — 59
D — 26
E — 53
F — 58
G — 97
H — 93
I — 23
J — 84
K — 62
L — 64
M — 33
N — 83
O — 27
P — 95
Q — 02
R — 88
S — 41
T — 97
U — 16
V — 39
W — 93
X — 75
Y — 10
Z — 58
Holmes shouted in triumph when he had completed the table. “Look!” he cried, “using the numbers of pi as a replacement code for the letters of the alphabet makes G and T the same number—97. It is not necessarily A_T _ _T. Either of the T’s may be—by Jove it is—a G. It is August! The second message says August—the same word as von Bork had as the password to his safe—and the last message says ‘Der vierte August um null vier null’ or ‘the fourth of August at four a.m.’”
“But the fourth message starts with Luttich?” said Gregson, catching swiftly on. “What is Luttich?”
“It is the German for Liège,” replied Holmes instantly. “That message can be translated as ‘Liège, Namur, Dinant’. Let me summarise all five messages.
‘95, 23, 95, 23, 95, 23’
Pi pi pi—as we speculated, this must have been a pre-arranged signal to selected senior German officials that the pi code, as must have been communicated to them previously, was about to be used to carry exceedingly sensitive messages.
‘31, 16, 97, 16, 41, 97’
August—this told the senior German officials the month when an attack was likely to take place. It is a weakness of the code that “G” and “T” are the same although this should not be a major obstacle to a code used for the shortest and most secret messages.
‘31, 64, 97, 31, 33, 27, 83, 97, 23, 83, 97, 53, 58, 31, 93, 88X
Altamont in Gefahr—means Altamont in danger.”
“Your bait worked, Mr Holmes,” interrupted Mr Asquith, “but you had no way of recognising it.”
“Another weakness of the code,” continued my friend, “is that the number of letters in the message must be divisible by three otherwise the coder has to fill the gap with an invented character. The X at the end of this message was screaming that at me. Fool I was not to realise it although I am flattered that the Germans considered my work so important that they used their special code when they thought I was in peril, and risked its security by making a modification to it which compromised it.”
Holmes turned to the last two messages and decrypted:
“‘64, 16, 97, 97, 23, 59, 93, 83, 31, 33, 16, 88, 26, 23, 83, 31, 83, 97’
Lüttich—as I said, the German for Liège, Namur, Dinant—communication of the direction of the planned German advance
‘26, 53, 88, 39, 23, 53, 88, 97, 53, 31, 1
6, 97, 16, 41, 97, 16, 33, 83, 16, 64, 64, 39, 23, 53, 88, 83, 16, 64, 64, 83, 16, 64, 64’
Der vierte August um null vier null null—being the date and time of the first assault—the 4th August at 4 o’clock in the morning.”
Holmes turned to Asquith. “The key message is that the Germans will attack Belgium at 4 a.m. on the 4th of August striking at Liège and Namur before swinging south to Dinant. The attack will start in,” Holmes glanced at his watch, “twenty-seven hours’ time. I would beg you, Prime Minister, to waste not a second in advising our French allies of this plan. I would also plead with you to give the Germans no reason to think that their code has been decrypted. Who knows what they might use it for next?”
“How do you suggest I do that? If our troops are moved to meet this attack, they will know the code has been tracked.”
“Could a plane not be used? A plane could fly up over German territory and see the German armies poised to strike across the Belgian border. If one were seen by the Germans and their attack were anticipated, that would give the Germans no reason to think that their code had been broken.”
“You seem, Mr Holmes, to be possessed of powers that are barely human.”
The Prime Minister was soon on his way, while Holmes and I retired to Queen Square.
We sat smoking cigars and Holmes said, “I fear my temporary deception by the German stratagem of putting commas between every three numbers rather than, as one would expect, between every two, is only explicable by the fact that I was working on a separate case at the same time.”
“But you seem to have got everything right,” I protested.
“But too slowly. My monograph points out that a delay in decryption is nearly as dangerous as a failure to decrypt. I have failed my own test.”
Maybe it was the passing of years, maybe it was a premonition of the slaughter that was to follow, but I have never seen my friend as downcast as he was at this moment which had, uniquely, seen two triumphs for him.
The Redacted Sherlock Holmes, Volume 6 Page 8