The Man Who Broke Napoleon's Codes

by Mark Urban

  Going back to the first part of the second paragraph of Dorsenne’s letter: if 516 on its own means ‘that’, then 1264 is likely to be another individual. Attacking these passages, something begins to emerge: that numbers from 1201 onwards denoted individuals, names of particular armies and places.

  It may be recalled that several months before, when the grand chiffre arrived at Joseph’s headquarters, it had consisted of a 1750-type cipher table of 1,200 numbers previously filled out in Paris. In expanding the table to include terms used in Peninsular warfare (by the simple expedient of glueing on a further two columns of 100 numbers each) the staff officers responsible had made the mistake of adding their new codes entirely in the columns marked 1201 to 1400. So 1201, the first of the coding numbers created by this expedient, stood for Malaga, 1202 for Valladolid and various other numbers for the commanders and armies found in the Iberian theatre of war. Certain military terms were also contained in this glued-on appendix of ciphering numbers. For example, 1330 meant ‘gunpowder’; 1392 was the French National Guard.

  It would have made more sense for Joseph’s Staff to have created a completely new cipher in which these terms were spread throughout the numbering as a whole, rather than being mostly confined to those between 1201 and 1400. Evidently, secret writing was a strange alchemy to the officers of Joseph’s Staff and they did not feel confident enough to alter the basic table they had been sent, since it was evidently the fruit of endless cogitation by the savants at the Foreign Ministry. The effect of all this was that before Major Scovell or Wellington had ever clapped eyes on this Great Cipher, it had been weakened, albeit slightly. It was not the case that all Peninsular terms and names were confined to that limited range of codes, because the original diplomatic code (sent out from Paris) did have entries for Madrid (it was 505) and a few other relevant places.

  Nevertheless, as the first few messages in the new code were being studied at Fuente Guinaldo, a French staff officer’s decision to add the extra two columns to the 1750 cipher table, increasing it to 1,400 numbers, was already showing its effects in the similarity of the two names or titles: 1207 and 1264. Looking back to the first paragraph of Dorsenne’s message, 1238 appears in a context that strongly suggests it can only mean something like ‘my command’, ‘my corps’, or indeed ‘the Army of the North’.

  As Scovell had scribbled in his notebook copy of Conradus, breaking these complex ciphers required the decipherer to know as much as possible about the affairs of the enemy camp. He would soon discover something about Dorsenne’s relationship with the authorities in Madrid that would open up more of the meaning of that letter of 16th April. In any event, the emergence of a good working theory about common codes (like 13 or 516) or proper nouns and military names (1207, etc.) was a very limited start to breaking the Great Paris Cipher. Even if deduction or just plain guesswork was to produce the meaning of a long string of code numbers bar one, that single unknown quantity – for example, the destination of a military movement or the date of its arrival – might render the entire work of decipherment worthless.

  There was something else helping the decipherer to expand his knowledge of what was going on in the enemy camp. Since Marmont was assuming many of his messages would fall into British hands, he could use the uncoded passages to say some things directly to his enemy, en clair, and others, in code, to his masters. Marmont wanted it clearly understood by whoever read his letter of 22 April that he had not been intimidated out of Portugal by Wellington. At the time he had gone, some parlementaires, allied officers under flag of truce apparently seeking to exchange prisoners, had ridden out to the French lines and made much of the imminent arrival of Lord Wellington’s army. Marmont wrote in his letter, ‘this news was given affectedly by parlementaires and we haven’t seen anything other than the single 1st regiment of hussars’. Marmont signalled also, to Berthier and the British, that he had not been seeking a general action with the allies when he crossed into Portugal and had not retreated because he feared one. He also revealed that he considered he had been sent on an ill-conceived mission, writing en clair, ‘your highness may judge from this that the results of the diversion that I tried to make in support of the Army of the South are more or less nil’. In this way, the French commander, unable to sublimate his intellectual pride, began quite deliberately sending interesting pointers to Wellington and Scovell. Had they been able to read that clutch of coded dispatches in their entirety, they would have learned much about the alarm of the French command and its fears about where the British might strike next.

  *

  After Badajoz, Marshals Soult and Marmont both expressed the same conviction in their letters to Paris and Madrid: ‘Wellington will attack me next, the other French army must come to my help.’ There was hardly a general in Spain who had not reflected on the emperor’s imminent departure for Poland and drawn conclusions about what it meant for their own expectations. Napoleon would be taking his chosen commanders on an odyssey that promised easy victories (how could Soult forget his moment of glory pummelling the Austrians and Russians at Austerlitz, after all?), opportunities to enhance their reputations in the eyes of wider society and abundant plunder. This sense, growing for some months, that they had missed the Russian boat while becalmed in this ghastly Spanish war, led most of the key protagonists in the Iberian Peninsula to try to resign their commands in late 1811 and early 1812. Marmont had tried to do so through his ADC Colonel Jardet when he went to see Marshal Berthier in Paris. King Joseph had once again been threatening to abdicate (prior to receiving the supreme command). Jourdan could hardly have left so soon after coming out, but had made clear his extreme reluctance to go there in the first place. Jourdan’s appointment as Chief of Staff had itself brought Soult close to resignation.

  The spirit of these officers was summed up by General Foy’s request to be relieved of the command of his division in a letter to Marmont: ‘I ask to be posted to another army and the greatest favour I can request is to be sent somewhere with greater opportunities for manoeuvre, danger and glory.’ Although busy preparing his campaign against the Russians, the emperor detected these signs among the protégés he had abandoned in Spain. Through Berthier, he had written back to Marmont, for example, on 16 April, ‘I have prescribed the specific measures necessary to take the initiative, and give the war a character that conforms to the glory of French arms and ends these meanderings and vicissitudes, that already seem to announce a defeated army.’ To pep up the forgotten army, Berthier ended his dispatch: ‘on his return from Poland, His Majesty will go to Spain; he hopes that he will only be able to praise what you have done, and that you will once again merit his approbation’.

  By April 1812, those sitting on the Portuguese frontier knew that Wellington had gained the initiative and that, notwithstanding Berthier’s flowery prose, the emperor would forget about them entirely for months unless, perish the thought, they fell victim to some disaster. It was time for each army commander to look to his personal interest first.

  Wellington himself, sitting at his desk in the Mayor of Fuente Guinaldo’s house, had not yet decided where he would strike. The British commander wrote a letter to his brother in Cadiz, hoping that the repairs on Ciudad Rodrigo’s defences would soon be complete and adding, ‘I don’t yet despair, between ourselves, of being able to undertake the expedition into Andalucia this year.’ Wellington, like some of the French superior officers, had half-expected that the fall of Badajoz might precipitate an evacuation of the south by Marshal Soult. Remaining where he was exposed Napoleon’s commander in southern Spain to the risk of having his line of withdrawal on Madrid severed by the British.

  Still, Soult, for reasons best known to himself, was staying put. Wellington understood from intercepted letters that the French were so desperate for supplies that the Army of the South would have difficulty resisting any move he made until the Andalucian harvest had been reaped in June or July. Just as he had carefully calculated the positions of French troops
before launching his attacks on the border fortresses, so the British general now had to consider what he could achieve in the time available before the crops were in, whereupon the enemy armies might combine to oppose him in southern Spain. Should he perhaps forget Soult and directly attack Marmont instead? The harvest came a little later in the north: that bought him a week or two more to fight the Army of Portugal that lurked just inside Spain on favourable terms. It was also true that if he fell upon Marmont, Soult was less likely to march north, for the man was notoriously self-centred. The Army of the South also had many troops committed to preventing revolt in the Spanish localities and this made it harder for them to assemble a few divisions quickly.

  One thing was clear to Wellington: whether he hit Soult first or Marmont, he needed to stop them helping one another. A French pontoon bridge had been built over the River Tagus at Almaraz, roughly halfway between the two French forces. Some magazines had also been established nearby, as he had learned from captured letters. Demolish the bridge and the French would have to go much further upstream, most of the way east to Madrid in fact, to help one another. Destroy the magazines and it might mean any French reinforcements would have to turn back. Even before the siege of Badajoz, Wellington had thought about sending the commander of his detached corps in the south, Lieutenant-General Rowland Hill, to attack Almaraz. This raid could only be launched if the British were sure that this area was weakly garrisoned.

  On the last day of April, one of Marmont’s messengers was seized by Don Julian’s lancers on the road from Salamanca to Madrid with a packet of letters: one of them was a note en clair about the imminent dispatch of Lieutenant-Colonel Colquhoun Grant to France for imprisonment. Wellington had already received at least one smuggled note from the prisoner and knew he was being held in Salamanca. The intercepted letter recorded Marmont’s lack of interest in a possible prisoner exchange. Knowing that all hope of getting his intelligence officer back by such means was gone, the general sent messages to various guerrilla commanders, promising a generous reward to the man who sprung Grant from captivity. None, however, was able to achieve this, and Colquhoun Grant was soon on his way back to France under heavy escort.

  Despite this, it was the other elements of Don Julian’s haul that caused Wellington to move into action. A letter to Jourdan, although it had been partially ciphered in the grand chiffre, gave an indication that Marmont’s forces were suffering from serious difficulties of supply.

  Marmont’s letter had been rather well enciphered, so its transitions in and out of code did not give a huge amount away. Had the British Staff been able to read it, they would have learned much about the Duke of Ragusa’s operational problems. He made a great deal of the shortage of rations that meant his army was so dispersed that it would require twenty-five days to concentrate and move to the assistance of Soult in the south, whereas the British could switch their axis of operations in just five days. It was, in effect, a carefully constructed and longer version of a theme that was becoming familiar to Jourdan from his other correspondents, Dorsenne, Marmont, Soult and Suchet: their own problems being so immense, they should not be expected to give any great help to anyone else. For the moment, though, the grand chiffre was protecting much of that information successfully.

  The very fact that there were passages en clair, however, allowed Wellington to learn something of its import. Revealingly, at one point Marmont had written, ‘I am staying at Salamanca until I am better instructed as to what 164.516 …’ and, after the coded passage, picked up, ‘with more considerable forces than those that I have until I am certain that Lord Wellington has established his HQ on this frontier’.

  It could be deduced from the marshal’s letter that he was staying put pending a discussion with Jourdan and Joseph of the next strategic move. Knowing from his other sources of information that the Army of Portugal’s southerly deployments were not particularly strong, the British commander saw that the moment had come to strike at the junction of the two main armies opposed to him, on the River Tagus just across the Spanish frontier. Wellington realized that an opportunity had been presented and on 4 May sent orders to General Hill to move quickly to destroy the bridge at Almaraz.

  NOTES

  1 ‘Outside the Exchange, the volunteers of the city militia daily changed guard’: this detail, and much else in this description of Lisbon, comes from Recollection of the Peninsula by Moyle Sherer. This officer was an unusual diarist, confining his accounts of battles to a page or two and devoting great passages of descriptive writing to the country and people, providing details which are hard to pick up elsewhere.

  2 ‘Major Scovell’s leave had only been possible because the main army would take a week or ten days to make its way back’: Scovell’s own journal (WO37/3) makes clear he was only allowed to go under these terms.

  3 ‘Marmont’s guest was none other than Lieutenant-Colonel Colquhoun Grant, Wellington’s intelligence officer’: Grant related these details to Sir James McGrigor, his brother-in-law and Wellington’s chief surgeon, who left his own Peninsular memoir, mentioned above.

  – ‘militiamen and Don Julian Sanchez’s guerrillas had swarmed about the French rear’: we are now entering the phase of this story where Scovell’s papers at the Public Record Office, WO37, contain most of the relevant original documents.

  4 ‘the way the English conducted themselves’: from Marshal Soult’s letter to Berthier, 17 April 1812.

  – ‘It took him just three days to travel from the Portuguese capital to Fuente Guinaldo’: Scovell’s journal again.

  – ‘Wellington remained in the mayor’s handsome house in Fuente Guinaldo’s plaza’: the building is still there. Alas, when I visited, the lady who owns the part of the building that Wellington had used as his office was out.

  5 ‘it was a matter of cho0sing in which direction’: Wellington’s Dispatches make clear that he had not finally made up his mind which way to attack until mid-May.

  – ‘Further study also allowed certain deductions to be drawn from the messages’: these observations about the pattern of the cipher are mine. Scovell’s notebooks give a general sense of how he attacked the codes but are not so specific as to tell us, for example, which code number he worked out first. Having worked on the French originals for months, I can say, though, that once familiar with the patterns of these letters, the recurrence of numbers like 13 or 210 pretty much leaps out at you. It becomes the fastest way of checking quickly whether the letter in question is in Joseph’s grand chiffre or some other code.

  6 ‘Since Marmont was assuming many of his messages would fall into British hands’: in a letter of 6 July 1812 to Jourdan (it is in the Scovell Papers), Marmont says explicitly that pretty much everything he writes ends up in enemy hands. He was just hoping that one of the duplicate or triplicate messages would actually reach its addressee as well.

  7 ‘There was hardly a general in Spain who had not reflected on the emperor’s imminent departure for Poland and drawn conclusions’: this is apparent, for example, in Jardet’s letter to Marmont cited in the previous chapter. The expectation of the Russian war was so widespread that cleverer British officers were reflecting on it in their journals of spring 1812, too; Cocks and D’Urban being two examples.

  8 ‘The harvest came a little later in the north: that bought him a week or two more to fight the Army of Portugal’: Wellington discusses the question in these terms in a letter to Lieutenant-General Graham on 24 May 1812, reproduced in Dispatches.

  9 ‘On the last day of April, one of Marmont’s messengers was seized by Don Julian’s lancers’: that they were responsible for the coup emerges in McGrigor’s journal.

  1. DONT. 1082. 365. 622. WE. W. 439. 669. E. 1085. 398. 326. DECEI. 1085. ED. 481. T. 980. 985. 186. T. 843. 688. AND. 1297. 536. 174. 1085. 1024 … 713. T. 980. 854. E. 326. 536. 700. W. 171. 1015. 1003. DE. T. 980. 1015. 131. T.

  CHAPTER TWELVE

  The Salamanca Campaign Opens

  Early on the morni
ng of 19 May 1812, soldiers of the 71st and 92nd Highlanders found themselves stumbling about in a steep-sided ravine close to the Tagus. The sun had yet to warm the still air, but the men were clammy from the unhappy combination of a humid season, red woollen coats and a heavy burden of impedimenta. The men of this British brigade were carrying scaling ladders, for the Almaraz bridge was protected by small forts. They had tried to move into position before dawn, but the country was so difficult that ‘when daylight … at length showed us to each other, we were scattered all over the foot of the hill like strayed sheep, not more in one place than were held together by a ladder’. Amid much whispered Gaelic cursing, the sergeants tried to bring the soldiers together, fearful that at any moment their presence would be discovered and the morning calm would erupt into gunfire.

  Almaraz’s bridge was defended by a fort at each end. The larger, Fort Napoleon, was the first target objective. Several miles away, the crossing was overlooked by three smaller posts along the Mirabete ridge. These positions had a breathtaking view over the valley of the Tagus and dominated the pass through which the French army’s traffic, both north and south, would have to go. As the morning air warmed, eagles began circling the Mirabete ridge, their great spread of wings banked to keep them inside the rising draught of warm air, their eyes scanning left and right in the perpetual search for prey. Neither the men in the forts on the ridge nor their avian companions would have spotted the Highlanders that morning, though. The British raid had been carefully planned, and the soldiers were bypassing the Mirabete and making their way behind a small ridge that screened them from its far-off look-outs.