The Decisive Impact of French Military Intelligence on the German Marneschutz-Reims Offensive

David Retherford and Richard Willis

July 15th 1918 saw the start of the fifth and final German offensive of the First World War. On that day, the Germans launched the opening phase of the Second Battle of the Marne, Codenamed Operation Marneschutz-Reims, shifting the entire momentum of the war from the Central Powers to the Entente. One of the key factors contributing to this shift was tactical combat intelligence.[1] This article reviews the process of analysis and dissemination of that intelligence.[2] Professional military education (PME) or specialist readers will find this battle and the subsequent shift in momentum interesting and generalist readers will be similarly engaged by an intelligence-driven narrative.[3]

Ludendorff in his study at the General Headquarters (German Federal Archives/Wikimedia)

By the middle of 1918, the Germans were looking for a knockout blow whereby the Entente would be forced to seek peace.[4] First Quartermaster-General Erich Ludendorff detailed the attack on June 14th: the Seventh Army would attack the River Marne area (the Marne defence element) around Mery, whilst the First Army would attack east of Reims, with July 10th earmarked for an attack along a seventy-four mile (113km) front.[5] The attack was intended as a diversion, with the main target another attack further north in Flanders planned for early August—Operation Hagen. The aim was to cross the Marne and deceive the allies into believing the target was Paris so the French and British would rush their reserves to protect the French capital, causing panic amongst the French population.

A month of preparation afforded the opportunity to complete meticulous plans, but it also had two unfortunate side-effects. First, the extended planning permitted Ludendorff to broaden the original scope into a larger operation requiring significantly more manpower. Second, events on the ground meant that soon after the plans were drawn up, they had to be scrapped and re-drafted. Although part and parcel of the war, it was noticeable that many divisions were ordered to move to new locations, only for these orders then to be changed and sometimes changed again—often after they had commenced the movement—causing disruption, delay, and frustration for the troops involved.

Military intelligence played a key role in supporting the planning for the offensive and was the responsibility of Department Abteilung IIIb, reporting to Oberste Heeresleitung, German Supreme Army Command. The blame for the failure of the offensive can be traced back to systemic and operational failures evident within Abteilung IIIb, while poor army discipline and chance also played a part. Although the Deuxième Bureau, French Military Intelligence, used the same sources and types of information available to all belligerents—namely interrogation of prisoners, aerial reconnaissance, visual observation, captured documents, and espionage—it demonstrated a superior ability to interpret the resulting intelligence compared to Abteilung IIIb.[6] 

The four previous offensives followed a similar pattern of attack. The Germans used tactical surprise with three key components: place, time, and weight.[7] Drawing on this experience, the French High Command believed they knew what to expect once the attack began. But the key would be to obtain information about the exact location and, just as important, the date of the attack. Understanding the strength and size of the attacking force would also help determine the requirements of any defensive response.

Unlike the Germans, who were obsessed with knowing which Entente division faced German positions, the French were not particularly interested in this level of detail. The French drew from previous offensives that the majority of German shock troops arrived at the front line at the last minute—just before the attack—making prior identification of units in line a pointless exercise. It was therefore important for the French to push intelligence-gathering into rear areas using distant aerial reconnaissance to identify more general movements of troops and supplies.

Despite being expressly forbidden to do so by Ludendorff, on June 30th a German pioneer officer swam across to the south bank of the Marne and was duly captured.[8] This was the intelligence breakthrough the Deuxième Bureau had been looking for. The pioneer officer’s interrogation revealed the exact location of the next German offensive and an approximate date of early July. This was then confirmed by French spies based in Madrid—in neutral Spain—as likely to take place on July 4th. However, no attack came on that date and the Deuxième Bureau directed the Fourth Army to re-double its efforts and send out further raiding parties to capture documents and prisoners.

The French ordered every division along the 31-mile front held by the French Fourth Army to participate in raids to capture German soldiers, particularly officers, with a focus on obtaining information on what they knew about the planned German offensive. A study by the French Sixth Army circulated on July 4th indicated an attack was scheduled for the 9th between Reims and Château-Thierry.[9] This included knowledge of the woods in which the troops were already assembling and a noticeable increase in aircraft and vehicle traffic in the area. Thirteen prisoners captured on July 5th and 6th in the area east of Suippe presented further evidence that an attack was imminent.[10] Despite freely passing over details of the attack to French authorities, the prisoners all gave a remarkably consistent story, which aroused the suspicion of the Deuxième Bureau. But the story also contained elements of fact, which the Deuxième Bureau was able to piece together, indicating the geographical location of the attack to be Reims. A day later, three escaped French prisoners crossed back to French lines—all confirmed an imminent German attack. Little by little, the Deuxième Bureau eliminated options and narrowed the likely location of the attack, improving the chance of intercepting the advance.

German prisoners being guarded by Australian troops, 23 April 1918. (Imperial War Museums/Wikimedia)

By July 10th, the Deuxième Bureau was confident enough to publish an intelligence report stating a German attack of 28 divisions would cross the Marne around the 14th between Jaulgonne–Vrigny in the direction of Epernay. Simultaneously, there would be an attack by 16 divisions on the front Suippe–Main de Massiges in the direction of Châlons and a third attack on the front Pompelle–Suippe by 14 divisions.[11] This was confirmed by further prisoner captures, revealing the offensive was codenamed Friedensturm (the Peace Offensive) and the attack would be on a 93-mile (150km) front to the west and east of Reims, while the city itself would not be attacked head-on.[12] A series of violent explosions at ammunition dumps between July 7th and 11th was further evidence that additional ammunition had been brought near the first line and was already in position. Large numbers of Minenwerfers with copious ammunition supplies nearby were located in K2 and K3, the second and third combat trenches, together with extremely large numbers of machine guns just north of the river.[13]  An interrogation report dated July 12th explained that soldiers had been captured with a three or four day reserve of food. What at first might seem mundane was in fact a strong indication of the impending date of the attack. Furthermore, July 14th was Bastille Day, a French national holiday, and this was considered significant because of the chance that the French population might temporarily let their guard down whilst celebrating.

A raid executed by four officers and 170 men from the French IR366th under the command of Lieutenant Balestie at 19:55 on July 14th captured 27 prisoners from the 73rd and 19th Reserve Divisions and the 7th and 11th Minenwerfer battalions.[14] Amongst the captured documents was a map of the complete Minenwerfer system including firing directions and objectives. But it was an  accidental behaviour by a captured German prisoner that finally gave the game away. An officer and 19 men from the German 19th Reserve Division were captured in the French Fourth Army sector at 21:30 on the 14th and insisted on having their gas masks urgently returned to them.[15] Suspicious, the guard enquired why the Germans required their gas masks. Realising he had unwittingly revealed that a German attack was imminent and that it would involve gas, the prisoner then admitted that an attack would commence with an artillery preparation involving large amounts of gas at midnight for four hours, followed by an infantry assault protected by a rolling barrage.[16] This final piece of the jigsaw was urgently communicated up the chain of command, giving the French just enough time to organise their own artillery attack. At 23:45 this was passed from French XXXVIII Corps to the US 3rd Division on the front line east of Château-Thierry.[17] At 23:50, just ten minutes before the intended German offensive was due to commence, pre-plotted artillery opened up on known assembly points packed with soldiers ready to go over the top and counter-battery fire on German artillery positions, causing widespread casualties and explosions at several ammunition dumps.

German soldiers advancing past a captured French position, between Loivre and Brimont, Marne department, 1918 (Wikimedia)

The German hammer fell at midnight on July 15th 1918, with units managing to cross the Marne later that morning. The momentum had been with the Germans after each offensive, but this time the Allies not only withstood the barrage but, thanks to a more effective defence in depth system, were able to break up the attack and reduce its effectiveness. It lasted three more days, but even on the 16th Ludendorff admitted defeat and issued orders to suspend the offensive south of the river and to continue it only in the vicinity of Reims. According to historian Jonathan Boff, “when Marneschutz-Reims began on July 15th, it did not go at all [according] to plan.”[18] Furthermore, historian David Zabecki stated that one of the critical failures of the German offensive of July 15th was the lack of surprise.[19] The battle is generally acknowledged as being the turning point of the war, signalling the end of the German military capacity to wage offensive operations. Three days later the allies launched their counter-offensive, and from that day until the Armistice, the momentum had swung from the Central Powers to the Entente. The German Chancellor, von Hertling later said, “We expected grave events in Paris for the end of July. That was on the 15th. On the 18th even the most optimistic among us understood that all was lost. The history of the world was played out in three days.”[20]


While it is true that combat intelligence did not fire any artillery rounds or break up any infantry attacks, it did place timely and actionable information in the hands of French decision makers. But it was not just that the German plan failed to be carried out properly or that elements of the plan were clearly fundamentally flawed. The failure had as much to do with the fact that the plan had been uncovered by the Deuxième Bureau allowing Entente pre-emption as it did with any limitations in German execution of that plan.

David Retherford Has an undergraduate degree from the University of Florida and a masters degree from Birmingham University. David is currently working on a second masters with a focus on research on American intelligence gathering during the First World War.

Richard Willis has a PhD in Strategy and Organisation change from the University of Newcastle and a degree from the University of Aberdeen. Richard is currently working on a monograph of the AEF and BEF fighting with the French Tenth Army during the Second Battle of the Marne.

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Header Image: Map of the final German offensives on the Western Front (World War I), 1918 (USMA/Wikimedia)


[1] Heymont, Irving. Combat Intelligence in Modern Warfare. (Harrisburg: Military Service Division The Stackpole Company, 1960). p6.

[2] Heymont, Irving. p6.

[3] Neiberg, Michael. The Second Battle of the Marne.  (Bloomington: Indiana University Press, 2008). p 131.

[4] Neiberg, Michael. p77.

[5]  United States. General Service Schools, and Conrad Hammons Lanza. The German Offensive of July 15, 1918 (Marne Source Book). Fort Leavenworth, Kan.: The General Service Schools Press, 1923. p.11-12; Zabecki, (2004), p.460.

[6] Gauché, Capitaine (1924), ‘La recherche du renseignement avant la bataille du 15 juillet 1918,’ La Revue d’infanterie, December, p.831.

[7] Falls, Cyril. The Great War. (New York: G.P. Putnam's Sons, 1959). p349.

[8] Ludendorff, Eric (1919) Ludendorff's own story, August 1914-November 1918; the Great War from the siege of Liège to the signing of the armistice as viewed from the grand headquarters of the German Army, p.308.

[9] Marne Sourcebook. p.383.

[10] Gauché, p.813.

[11] Note 2e bureau / GQG n ° 9056 », citée au SHD / GR et au 16 nº 917:« Relevé chronologique et analyse succincte des principaux ordres, instructions, directives et études concernant la recherche et le traitement des renseignements personnels au cours de la campagne », GQG / 2e bureau, 17 juillet 1919

[12] Marne Sourcebook, p.298. Gauché, p.814.

[13] Gauché, p.827

[14] Revue Militaire Francaise (1923) Un coup de main historique exécuté par la 132e DI le 14 Juillet 1918.


[16] This was 01:00 German time.

[17] Marne Sourcebook, p.645

[18] Boff, Jonathan. Haig’s Enemy. (Oxford: Oxford University Press, 2018). p231

[19] Zabeki, David. The German 1918 Offensives. (New York: Routledge, 2006). p.254,p.271,p.273

[20] Von Hertling cited in Pershing John J My experiences in the World War. Volume II 1931, p.472.