Absolute Numbers: The Schlieffen Plan as a Critique of German Strategy in 1914

I. Relative Numbers

The German war plan in 1914 proposed an attack on France by way of Belgium and Luxembourg to outflank the enemy fortifications that extended along the Franco-German border from Belfort to Verdun. This attack would be carried out by 26 corps, with 8 more engaging in subsidiary operations in Alsace-Lorraine, ¹ so the ratio between the right wing and the left was roughly 3 to 1. Ever since the 1920s it was thought that this order of battle represented a departure from the famous Schlieffen plan of December 1905, ² in which the corresponding force ratio was supposed to have been a massive 7 to 1. The evidently hypnotic idea that Schlieffen concentrated seven-eighths of his army on the right wing goes back at least as far as Wolfgang Foerster’s Graf Schlieffen und der Weltkrieg, published in 1921. ³ It appeared again in 1925 in volume 1 of the official German history of the Great War, ⁴ and it has survived all the way down to volume 1 of Hew Strachan’s history of the Great War. ⁵ Through constant repetition over the decades it has achieved the status of common knowledge. ⁶ Holger Herwig was simply falling in with a universal consensus when he said recently that in 1914 the younger Helmuth von Moltke ‘reduced the relative strength of the right wing from Schlieffen’s 7 : 1 to a mere 3 : 1’, adding that this change was a ‘critical shift of forces’. ⁷ But in spite of its enduring currency, the tale of Schlieffen’s sevenfold preponderant right wing rests on a plain misunderstanding of the Schlieffen plan. One whole army that is usually counted as a part of the right-wing attack through Belgium operates in fact as a part of the left wing in Alsace-Lorraine.

Schlieffen himself must take some of the blame for this confusion. He proposes to outflank the enemy border position, ‘of which the great fortresses of Belfort, Epinal, Toul and Verdun are the main strongpoints’. ⁸ To this end he says that 23 army corps (i.e. first-line formations, also called ‘active’ corps) and 12 and a half reserve corps will assemble between Metz and Wesel to ‘wheel left against the line Verdun–Dunkirk’. Included in this count, however, are 5 reserve corps that do not join in the advance on Verdun–Dunkirk, because their mission is to protect the southern flank of the main forces against an enemy counter-thrust ‘from the line Toul–Verdun’. ⁹ These formations do not take part in outflanking the border position, rather they directly confront a line between two of its ‘main strongpoints’. They are committed to opposing the fortress system, not going around it.

Although their function is in principle defensive, the five reserve corps also take on a proactive role in Lorraine. In the first draft of the Schlieffen plan they are to ‘advance as far as they can on the left of the Moselle against Verdun–Nancy’. The point of this threatening move is to ‘hold down as many enemy as possible on the original front’, in other words to keep the French in place behind their fortress line and prevent them from redeploying against the German right-wing attack. Meanwhile, the German forces on the east bank of the Moselle (three army corps and three reserve divisions) are to move forward with the same object – ‘to hold the enemy as far as possible behind the Moselle, so that he cannot move too many forces to his left wing’. They advance against the entire length of the Meurthe and the line between Lunéville and Pont-à-Mousson 30 kilometres north of Nancy, effectively linking up there with the five reserve corps closing in against Verdun-Nancy. ¹⁰ In this scenario the five reserve corps form part of a continuous chain of pressure exerted on the French border position all the way from Verdun to the Vosges.

In the final version of the Schlieffen plan the operations on the left wing are conceived rather differently, but the five reserve corps still have a critical role to play. Initially the German forces east of the Moselle (now comprising three and a half army corps and one and a half reserve corps) ‘will attack Nancy, in order to attract as many enemy as possible on themselves and away from the reinforcement of the northern front’, while the five reserve corps presumably keep to a defensive alignment west of Metz. Schlieffen describes Metz as ‘the strongpoint for covering the left flank’ and anticipates that it will ‘draw upon itself a considerable part of the enemy’s forces’. He clearly expected a French strike against the left flank of the main German army, in which case the five reserve corps, which are also instructed to ‘cover … the left flank’, would likewise draw in a good number of enemy troops and keep them from being used on ‘the northern front’. ¹¹ When two active corps are transferred later from east of the Moselle to the German right wing, the picture on the left wing changes considerably. The troops remaining on the east bank, possibly reinforced with two new corps, are given ‘the task of advancing on the Moselle between Belfort and Nancy’, whereupon the five reserve corps also take the initiative, their task being to ‘attack the Côtes Lorraines’, which implies a direct assault on the Meuse forts between Toul and Verdun. ¹² The mission of the five reserve corps is explicitly designated as an attack, not just an advance. They are massed on a narrower front than the German forces east of the Moselle, so their impact will be more powerful and hence more effective in tying down enemy forces. At this stage in the Schlieffen plan the five reserve corps actually constitute the Schwerpunkt of the German left wing.

These formations do not, then, participate in the outflanking attack through Belgium. Whether defensively or offensively, they operate in Lorraine against the northern sector of the border position, serving both to protect the left flank of the main German army and to prevent the enemy from sending more troops to oppose the main German attack. In virtue of their placement and their activities, the five reserve corps clearly make up an integral part of the German left wing, which means that the initial balance between the right wing and the left is 3 : 1, ¹³ not 7 : 1. When Moltke assigned three-quarters of his west-front army to the attack through Belgium, he was not deviating from the distribution of forces in the Schlieffen plan.

But we really ought to make another correction to the way we talk about Schlieffen’s ‘right wing’. This term is conventionally applied to all of the forces engaged in the attack through Belgium, and that is the sense in which I have used it above. But Schlieffen’s own usage does not follow that pattern. He speaks of ‘the main army’ ¹⁴ or ‘the main German forces’ ¹⁵ with reference to all of the troops that deploy west of the Moselle, and he also speaks of ‘the right wing of the German main army’, ¹⁶ indicating that the right wing is just one component of that body. How large a component is specified in a passage dealing with the need to make the right wing ‘as strong as possible’. It is ‘for this purpose’ that 8 army corps cross the Meuse below Liège and are joined by one more, the XVIIIth, after it has crossed the Meuse above Liège. These 9 active corps are screened on their right flank by a group of 7 reserve corps, ¹⁷ so Schlieffen’s right wing – in his own sense of the term – consists of 16 corps altogether. Moltke’s right wing, as defined in the Reichsarchiv history of the Great War, consisted of three armies ¹⁸ totalling 16 corps at the start of the German advance on 18 August 1914 ¹⁹ – exactly the same as the right wing in the opening phase of the Schlieffen plan.

Later on, however, at the moment of decisive battle, we find a marked disparity between the two right wings. By the time Schlieffen’s right wing approaches Paris it has relinquished all of its reserve corps: 5 remain in front of Antwerp, while the other 2 are either engaged in covering ‘the flank and the rear of the main army’ or else switched to the front line of the German centre. ²⁰ On the other hand, Schlieffen’s right wing now gains reinforcements in the shape of 2 active corps transferred from the left wing and 6 newly raised Ersatzkorps, ²¹ so the net result is a complement of 17 corps. By the eve of the battle of the Marne, Moltke’s rechter Flügel had left one reserve corps behind at Antwerp and another at Maubeuge, as well as forfeiting 2 active corps to the eastern theatre, so it now consisted of only 12 corps, 5 fewer than the right wing at the corresponding stage of the Schlieffen plan. But for those commentators who think the crucial matter was the relative strength of the right wing, that discrepancy can be made to vanish with a quick recalculation. As it approached the line between Paris and Verdun, Moltke’s right wing represented one-third of his forces in the west, almost exactly the same proportion as the right wing at the same point in the Schlieffen plan. ²² On that basis the ‘relativists’ could argue that Moltke fought the battle of the Marne with a right wing conforming to the specifications of the Schlieffen plan.

But that just goes to show the artificiality of the whole discussion about the relative strength of the right wing. No one would seriously equate the German right wing at the battle of the Marne with the right wing that carries out the decisive attack around Paris in the Schlieffen plan. Apart from the real numerical discrepancy, the most striking difference concerns the whereabouts of these forces. Moltke’s right wing was operating east of Paris against an enemy position connected to the capital city, whereas Schlieffen’s is in the process of outflanking that position by advancing west of Paris across the lower Seine. There is no operational congruity between these two ‘right wings’, so any comparison of their strength is really quite meaningless. Moltke had an empty space where the Schlieffen plan requires the right wing to be, so we might just as well say that he had no right wing at all in comparison with the Schlieffen plan. And the reason why Schlieffen’s right wing is positioned where it needs to be is that the absolute number of troops involved in the Schlieffen plan is much greater than it was in 1914, so the whole front can extend much further to the west than it did in 1914.

Let us turn, then, to the substantive issue of actual numbers and put aside the game of proportions and fractions by which Moltke’s plan can be made to look like that of his predecessor. In his December 1905 memorandum Schlieffen concludes that the German army would have to deploy at least 48 and a half corps of all types for an attack on France by way of Belgium. ²³ In 1914 Moltke planned a similar attack on France with 34 active and reserve corps, ²⁴ more than half a million men below the strength that Schlieffen had said would only just suffice. But here a different ‘relativist’ objection comes into play. Gerhard Groß and Annika Mombauer argue that such numbers should not be taken too seriously, as Schlieffen and Moltke both believed the superior quality of the German army would make it much stronger in effect than it was on paper. ²⁵ But that is another myth that needs to be put to rest.

Moltke did say in December 1911, in a memorandum to the German chancellor Bethmann Hollweg, that ‘wars are not decided by numerical strength alone’ and that such characteristics as bravery, efficiency, discipline, and good leadership ‘count for more than mere numbers’. But he qualified those remarks by adding that the moral element in war ‘cannot be gauged in peacetime’. He continued: ‘The only positive basis for assessing our chances in a forthcoming campaign is a comparison between the fighting strength of the two sides’. ²⁶ According to Mombauer, this passage conveys Moltke’s belief that ‘inferiority in numbers did not need to affect German war planning’, because the qualities of the German army ‘were thought to make up for any numerical inferiority’. ²⁷ In fact, Moltke’s argument went in precisely the opposite direction. He was saying that although the quality of an army might prove decisive in the event, that effect could never be calculated in advance and therefore it should never influence war planning, which must be based exclusively on quantifiable factors. His point was not that numbers didn’t matter in war planning, but rather that they were the only thing that did matter. He went on in the same memorandum to emphasize how seriously outnumbered Germany would be in ‘the great war that everyone expects to break out sooner or later’, and to warn the chancellor that a major increase in the size of the armed forces was ‘imperative for our self-preservation’. ²⁸

Schlieffen’s rejection of the argument from quality was even more emphatic. He saw it as a dangerous illusion and subjected it to a burst of his notorious sarcasm. Reflecting on Germany’s huge numerical disadvantage in a two-front war, he said that some people:

attach great importance to having a small, high-quality army. We have certainly fulfilled the first of these criteria, since we do indeed possess a relatively small army. But is it so good, so much better than other armies that it makes up in quality for the great numerical preponderance of the other side? What is this much higher quality supposed to consist of, in an age when the weapons, equipment and training of all armies are more or less the same? We may hope that our army is better than the French and Russian armies, but it remains to be seen whether the qualitative difference is as great as that between, let us say, Europeans and Red Indians or Negroes – because that is how much better we would have to be, considering the scale of our numerical disadvantage. ²⁹

Schlieffen did not deal in soft numbers that could be adjusted downwards by qualitative compensation. When he argued in December 1905 that the German army would need 48 and a half corps for an attack on France through Belgium, that is what he really meant.

II. Attack and Defence

All the same, we might think this was a rather excessive demand, considering how vulnerable France appeared to be. The Russo-Japanese War of 1904–5 turned out disastrously for Russia, leaving France with an acute strategic dilemma of its own. For some years from mid-1904 onwards it seemed likely that in a European war France would face Germany without effective support from its ally in the east. It was against this background that the French chief of staff, Jean Pendézec, issued a dire warning to foreign minister Delcassé in November 1904. Evidently discounting the possibility of Russian intervention, he said that if it came to war France would deploy the equivalent of 24 corps of all types against a German total of 38. ³⁰ Terence Zuber believes that by the end of 1905 that opportune moment for the Germans had passed and a one-front war was now a ‘rosy assumption’, ³¹ but in January 1906 the French military attaché in St Petersburg advised his war minister that ‘for the moment and for a certain amount of time to come, the Russian general staff cannot afford us de facto the support that it is engaged to give us’. ³² It still made sense for the Germans to prepare for a war against France alone as well as a two-front war, and the one-front deployment plan (Aufmarsch West I) for 1906/7 presupposed much the same disparity of forces as in Pendézec’s nightmare scenario. With the whole of their field army in the west, the Germans would deploy 52 active divisions and the equivalent ³³ of 27 reserve divisions against a French army estimated at 40 active and 15 reserve divisions. ³⁴ So the Germans in Aufmarsch West I were 24 divisions better off than the French, which appears to confirm David Herrmann’s view that Schlieffen was able to achieve ‘the extraordinary numerical superiority necessary for his outflanking manoeuvre’ by using every one of his active and reserve formations in the west. ³⁵ But for Schlieffen himself this was an open question, not a safe assumption. Would the entire German field army really provide a sufficient numerical advantage for the deep strategic attack he now contemplated? In the course of drafting the December 1905 memorandum he gradually built up a picture of the enemy’s formidable defensive capability. He did not think that the French would necessarily adopt a defensive strategy, but he recognized that this would be their best option and it therefore became the central theme of his analysis.

Schlieffen started work on his December 1905 memorandum by drawing a sharp distinction between the strategic offensive through Belgium and the earlier designs for a German attack in the west. He considered how the Germans might attack the border position in front and simultaneously try ‘to envelop the defender’s left flank’ (‘die linke Flanke des Verteidigers zu umfassen’). ³⁶ This idea was proposed in a memorandum Schlieffen wrote in October 1898 and in a study by his Oberquartiermeister III Hans Beseler in 1900. ³⁷ But in exercise critiques of 1904 and 1905 Schlieffen came to see this plan as a misapplication of standard field tactics to the special problem of overcoming a fortress system. He said that if one enveloped the flank of a field position while attacking it in front, that normally rendered the position untenable, but the same result could not be expected with the French fortress position, whose ‘cornerstone’ (Verdun) would not be dislodged by an envelopment. The radical alternative to the unpromising envelopment plan was ‘to outflank the fortified line completely’ (‘die befestigte Linie ganz zu umgehen’). ³⁸ In the first draft of the December 1905 memorandum Schlieffen repeated his misgivings about the Umfassungsplan. He said that the French anticipated such an attack and ‘will extend their front line leftwards to Mézières’ in order to obstruct it. Even if the difficult move around Verdun could be carried out, the enemy would still have ‘no need to give up the front Belfort–Verdun, since he would be covered there by his fortifications’. Rather, it was the German ‘enveloping army’ that would be in danger, since it could become ‘altogether separated from the main army’ and susceptible to counter-attack by superior enemy forces. Schlieffen concluded: ‘Only one course remains: to outflank the position completely’ (‘die Stellung völlig zu umgehen’). ³⁹

It is worth dwelling for a moment on this conceptual rethink. Schlieffen gave up the idea of enveloping the border position in favour of outflanking it. In descriptions of the Schlieffen plan these terms are often used interchangeably, which is another bad habit with a long history. One military writer complained in 1931 that ‘many people fail to appreciate the fundamental difference between envelopment [Umfassung] and outflanking [Umgehung]’, and then went on to explain what the difference was: ‘Envelopment aims at an immediate tactical effect by a part of the army, whereas outflanking is a preparatory move that aims to bring about the most favourable circumstances for a battle.’ ⁴⁰ Schlieffen was moving away from an essentially tactical plan to envelop the northern end of the fortress line with the smaller part of his army, and proposing instead a strategic offensive through Belgium to outflank the fortress line with the main body of his army and seek a decisive battle on the other side.

Under the shelter of his fortifications the enemy was deemed to be safe from envelopment, but the German outflanking manoeuvre would shift the fighting into open space, the proper sphere of envelopment operations, so then ‘the intention must be to envelop his left flank with a strong right wing’. The enemy might try to frustrate the German envelopment by extending his left wing, but then ‘he will so weaken his front line that a break-through at some point may well become possible’. ⁴¹ One way or another, it seems fairly certain in Draft I of the Schlieffen plan that French resistance is going to be overwhelmed by the power and scope of the German offensive. In Draft II Schlieffen concedes that the French ‘will not hesitate to shift troops from the main front to the endangered subsidiary front, or to move up reserves, for example the corps from the Alpine frontier’. But these reinforcements will not relieve the predicament of the French, as they are insufficient ‘to provide their left wing with the desired extension and strength’. ⁴²

But soon after this point Schlieffen’s assessment is thrown into reverse as he brings out further aspects of the defender’s strength. Let us consider a text that Ritter designates Fragment VII in his inventory of the Schlieffen plan materials. ⁴³ The problem here is that the French defence will be made much sturdier when ‘second-line troops [Reservisten] are brought in from every side’. The term ‘Reservisten’ does not refer to reserve units, but to the reserve category of personnel. Schlieffen clearly thought that the French would in the end make use of a large number of mobilized reservists not initially assigned to the field army. ⁴⁴ These reinforcements would be sent up to the front ‘to fill the gaps and to satisfy the increased demand’ ⁴⁵ – that is, to provide the enemy’s left wing with ‘the desired extension and strength’ which Schlieffen said in Draft II could not be achieved. Now he expects to encounter a French line of defence extending all the way to Paris without leaving any points of weakness where the Germans might penetrate. Schlieffen’s response is to declare that ‘the right wing of the German main army must attempt to [outflank] Paris on the south if necessary’, ⁴⁶ which is apparently the first time the circumvention of Paris is mooted in the Schlieffen plan materials. ⁴⁷ But it occurs in proximity with another quite new motif that puts everything in doubt: ‘Before the Germans reach the Somme or the Oise they will have realised, like other conquerors before them, that they are too weak for the whole enterprise.’ ⁴⁸

In Draft VI ⁴⁹ the plight of the attacker gets even worse as Schlieffen acknowledges that the French defence will be further strengthened by the deployment of territorial troops. This cannot be matched on the German side as nearly all the Landwehr brigades following the main army will by this point be occupied in observing enemy fortresses and guarding the lines of communication. ⁵⁰ The defender is free to use his third-line troops for the immediate purpose of defence, but the attacker’s third-line forces cannot be thrown into the attack itself as they are almost completely tied up with subsidiary functions of the offensive campaign.

In the same draft Schlieffen says that the Germans will ultimately face ‘a battle for the line Verdun–La Fère–Paris’, which represents a ‘second fortified line’, connected to the one between Belfort and Verdun. Subtracting the fortified zones from the length of front to be covered, and adding the territorials to the number of troops available to cover it, he reckons that the French could occupy the whole 500-kilometre line from Belfort to Paris with an average of four infantrymen per metre, a much greater density than the attacker could manage. Since five German reserve corps are detached for the investment of Antwerp, the remaining forces would amount to some 830 battalions, which gives an average of less than two rifles per metre. Schlieffen wonders whether Paris must be outflanked if the French position cannot be taken in front, but that now seems a purely academic issue: ‘When we reach this question, the thought will immediately present itself, if it has not done so already, that we are too weak for the enterprise we have undertaken.’ Echoing Clausewitz, Schlieffen explains why the balance of power has shifted so drastically in the course of the offensive: it is because the attacker’s strength ‘dwindles constantly, while the defender’s increases’. ⁵¹

There was a remarkable parallel in the thinking of Jean Brun, Pendézec’s successor as chief of the French general staff. He admitted in November 1905 that the French would have to stay on the defensive and give up a lot of ground to begin with, perhaps being driven back as far as the Seine or the Aube, but he drew encouragement from ‘la doctrine de Clausewitz sur le point limite de l’offensive’. The Germans would gradually lose strength in the course of their advance and eventually come to a standstill, which could give rise to a ‘renversement des forces’: as long as the defender had preserved his morale and his freedom of manoeuvre, the chances of success would suddenly turn in his favour. ⁵² Brun’s ‘point limite de l’attaque’ corresponds to Clausewitz’s ‘culminating point of the attack’, meaning a point where the attacker has exhausted his initial superiority and the two sides are in equilibrium. The ‘renversement des forces’ refers to a passage where Clausewitz says that if the attacker overshoots the culminating point, then ‘the scale is turned and the reaction follows with a force that is usually much stronger than that of the original attack’. ⁵³ The Schlieffen plan drafts can be read as a case study in Clausewitz’s theory that ‘defence is the stronger from of waging war’, ⁵⁴ and that analysis was shared on the other side of the hill – with the difference, of course, that it gave considerable reassurance over there.

The point about the dwindling power of the German attack is just as bluntly expressed in the final version of the memorandum. Here too Schlieffen says that the French will probably succeed in forming a redoubtable defensive line between Paris and Verdun, and whether they fight on the Aisne and the Oise or further back on the Marne or the Seine, they will probably hold their ground. To overcome the enemy position the Germans would need to combine a frontal attack with an outflanking move around the French capital, but that would entail the investment of this ‘gigantic fortress’ on its western and southern perimeters, leaving the forces available for the attack itself ‘considerably weakened’ and facing ‘a more numerous enemy’. In pondering how they could press on under these circumstances, the Germans would soon realize that they could not: ‘we shall reach the conclusion that we are too weak to continue operations in this direction’. ⁵⁵

Schlieffen considered that the Germans were not strong enough to defeat the French by an attack through Belgium, but that assessment related to the official strength of the German field army as set out in the Aufmarsch West I of 1906/7. The Schlieffen plan goes on to say that ‘still greater forces must be raised’, and then proposes a number of ways in which new units could be formed in wartime out of the mobilized resources of the German army. The most important measure would be the creation of eight new corps from the trained Ersatz or replacement troops. The raising of these formations is, Schlieffen says, ‘the very least we are bound to do’. Six of the Ersatzkorps are brought by rail to the German right wing to face Paris on the west and south and so provide cover for seven active corps as they march around the western side of the capital to outflank the French position. Another precondition of the outflanking manoeuvre is that the French must be pinned down by a ferocious attack all along their line of defence. ⁵⁶ Crucial to the effect of this frontal attack is the destructive power of the heavy mortars and howitzers at the disposal of the 18 active corps involved. The repeated bombardment and assault of the front will tie the enemy down while the outflanking move takes place. ⁵⁷ That would be the decisive battle of the whole campaign, releasing a quarter of a million first-line German troops against the enemy’s unprotected lines of communication and retreat. The final objective was to drive the surrounded French armies ‘eastward against their Moselle fortresses, the Jura and Switzerland’ and annihilate them. ⁵⁸

Schlieffen had worked out a method for overcoming a French defence in depth, but the outlay was enormous. The plan would need the whole of the German field army to be committed from start to finish, and the entire body of trained Ersatz personnel to be available for the decisive battle. It was a level of force requirement that made the plan totally impracticable in a two-front war. A war plan, after all, is not just a spatial idea that can be illustrated by arrows drawn on a map. The forces that the arrows represent must be strong enough to achieve in reality what the arrows accomplish on paper. The outlines of the Schlieffen plan are inseparable from the army of the Schlieffen plan, and such a force could not possibly be assembled in the west in a two-front war. This plan was for a war limited to the western theatre.

Gerhard Groß sets out a quite different view, based on a doctrinal argument. He asserts that Schlieffen was bound by his ‘strategic and operational credo’ to begin a two-front war with an attack on France, and that Schlieffen ‘announced’ this principle in his discussion of the 1901 Generalstabsreise Ost. What Schlieffen actually said on that occasion was that in a two-front war Germany

must begin by trying to overcome one enemy while merely keeping the other one busy; but then, when the first enemy has been defeated, the Germans must use the railway to achieve the same result in the other theatre of war – to gain a numerical superiority there that will prove fatal for the other enemy as well. ⁵⁹

Groß quotes this passage, but then – realizing that it says nothing about attacking anybody – he provides a supplementary note of his own: he tells us that Schlieffen’s object ‘could be achieved only through offensive and not defensive actions’, and that the attack had to be directed against France by way of Belgium. ⁶⁰ But if we examine the context of the quotation, it turns out that this is not at all what Schlieffen meant. The Generalstabsreise Ost of 1901 followed on from a Generalstabsreise West of the same year, in which the French – not the Germans – attacked through Belgium and Luxembourg and were decisively beaten by a counter-attack on the left bank of the Rhine near to the Belgian border. ⁶¹ It was this defensive victory that Schlieffen was referring to when he spoke of the need to crush one enemy first and then turn against the other. He insisted that the Germans ‘must wait for the enemy to emerge from behind his defensive ramparts, which he will do eventually. That was the approach adopted in this exercise, and the Germans won a decisive victory over the French’. ⁶² Schlieffen was putting forward the very opposite of the view that Groß attributes to him. There is no evidence here – or anywhere else, come to that – of a Schlieffen ‘credo’ dictating a strategic attack through Belgium in the case of a two-front war.

That may seem a rather bold statement, as Schlieffen is positively renowned for his will to take the offensive. The idea of attacking the enemy’s flank and rear is a constant refrain in his military writings. But we should be aware that he very often speaks of an attack when he means a counter-attack. Discussing the proper German response to a French offensive between Metz and Strasbourg, he insists that the invading army must not be driven back to its border position, but annihilated on German territory, and ‘that is possible only by means of an attack on the enemy’s flank and rear’. ⁶³ Whenever we come across that formula we have to take note of the context, which frequently reveals that Schlieffen is talking about a counter-attack in the framework of a defensive strategy.

Robert Foley agrees with Groß that Schlieffen was intent on attacking France in a two-front war, which he says can be deduced from the official German deployment plans for 1905/6. He notes that in the Aufmarsch West I for a war against France alone the entire German army would be deployed in the west for an attack through the Low Countries. In the plan for a two-front war the army in the west would be reduced by three active corps and four reserve divisions, but Foley says that this diminished force was also ‘deployed to advance against France via Belgium and the Netherlands’ and that Schlieffen ‘even provided for the rapid capture of the Belgian and Dutch rail network: 5 German cavalry divisions had orders to capture the bridges across the Maas and to secure the rail lines running from Germany’. ⁶⁴

The cavalry dash to the bridges at Venlo, Roermond, and Maaseyck would prove Foley’s point beyond all doubt – if only it were relevant to his argument, which it is not. The seizure of those particular crossings certainly indicates a line of advance through the southern Netherlands and central Belgium, but it comes under the heading of Aufmarsch West I, the plan for a one-front war, so it reveals nothing at all about Schlieffen’s intentions in the west in a two-front war. ⁶⁵ In fact, the source that Foley appeals to contains no information about that year’s west-front deployment in a two-front war, except for the number of units involved. ⁶⁶ He was perhaps thinking of the Aufmarsch West II for the following year (1906/7) when he deduced that the Germans intended to attack France in a two-front war, but even here the information is extremely sparse: all we have to go on is a bare order of battle showing the composition of the seven armies deployed in the west, but with no indication of their assembly areas or their operational tasks. Aufmarsch West I for that year is an explicitly offensive plan in which ‘the entire force, with the exception of 7th Army, will carry out a left wheel through Belgium’; but that is the directive for a war ‘against France alone’, and we cannot jump to the conclusion that it also applied to the alternative plan for a war ‘against France and Russia’. ⁶⁷

For support in this matter Foley could have looked to an argument advanced long ago by Gerhard Ritter, though that was also based on a dubious leap of logic. From Wolfgang Foerster’s evidence that the right wing in Aufmarsch West II was relatively just as strong as in Aufmarsch West I, ⁶⁸ Ritter concluded that it must have had exactly the same mission as in Aufmarsch West I. On the strength of this solecism he declared that ‘the great envelopment on the right was to be the programme whatever happened, even if the chances of success were greatly diminished by deploying troops to the East’. ⁶⁹

We cannot infer from the relative strength of the right wing in Aufmarsch West II that it was supposed to attack through Belgium. A relatively strong German right wing also made perfectly good sense as part of a defensive strategy. Friedrich von Boetticher pointed out that Schlieffen’s 1893/4 deployment included a strong right wing to oppose a French attack through Luxembourg. ⁷⁰ In 1898 Schlieffen said that the right wing must be made strong to counter a French attack that would probably come through Belgium and Luxembourg. ⁷¹ Herrmann von Kuhl recalled Schlieffen testing a scenario in which the mass of the French army conducted a great rightward wheel through Belgium and Luxembourg and against the lower Moselle, exposing its left flank to a German counter-attack from the direction of the Rhine. ⁷² That is apparently what happened in the west-front general staff ride of 1901. The French attacked through Belgium and Luxembourg and were decisively beaten on German soil west of the Rhine. ⁷³ That frontier victory over the mass of the French army must have required a very strong German right wing, so we cannot argue that such a deployment pattern necessarily signifies an attack on France by way of Belgium.

There is also some direct and categorical evidence against Foley’s thesis. In late 1905 Schlieffen remarked that the German army would be massively outnumbered in a two-front war and therefore could not mount an offensive in either direction. Even an attack against one opponent ‘would require so many forces and so much time that too little would be left over for a defensive against the other’. Under these circumstances the Germans must wait for their enemies to attack first and then try to beat them with counter-attacks in quick succession. ⁷⁴ Schlieffen delivered this unequivocal ruling on 23 December 1905. Eight days later, on 31 December, he wrote the first draft of his plan for the invasion of France through Belgium, but this was not a case of schizophrenia. Schlieffen’s thinking was by now lucidly polarized according to what kind of war Germany would have to fight. In a war against France alone he favoured an all-out attack, but in a two-front war he insisted on a purely counter-offensive strategy.

III. To the Marne

Faced with a two-front war in 1914, Moltke ignored Schlieffen’s advice and launched a strategic attack on France by way of Belgium and Luxembourg, only to be thwarted at the battle of the Marne. Moltke had written down some general observations on the Schlieffen plan in 1911, misconstruing it as applicable in a two-front war. He said that he agreed with ‘the basic idea of opening the war with a strong offensive against France while initially remaining on the defensive with weak forces against Russia’. By attacking through Belgium the Germans could ‘meet the enemy in the open’ so as to defeat him ‘quickly and decisively’ and then despatch reinforcements to the eastern front. ⁷⁵ Annika Mombauer has shown that this concept dominated Moltke’s strategic thinking in the pre-war years and at the start of hostilities, ⁷⁶ but she fails to discern those respects in which it was completely antithetical to the Schlieffen plan. In the first place, Schlieffen never proposed a strategic attack through Belgium in the event of a two-front war. The December 1905 memorandum deals with a ‘war against France’ in which Russia plays no effective part, ⁷⁷ so that the entire German army can be deployed in the west, and there is no eastern front standing in urgent need of reinforcements. Moreover, Schlieffen did not foresee the French being quickly defeated ‘in the open’ after the Germans had outflanked the border position. Rather, he thought they would fall back on a ‘second fortified line’ between Paris and Verdun, and to overcome that position the Germans would need forces greatly exceeding anything that could be deployed in the west in a two-front war. Moltke somehow convinced himself that he was following ‘the basic idea’ of the Schlieffen plan, and Robert Foley endorses that claim when he says that ‘Moltke stuck to the basics of Schlieffen’s 1905 memorandum’. ⁷⁸ But there can surely be nothing more basic to a war plan than the specification and provision of the means to put it into effect. What Moltke ‘stuck to’ in 1914 was the Schlieffen plan under the wrong circumstances, the outward form of the Schlieffen plan lacking the necessary substance – in short, a perversion of the Schlieffen plan.

Terence Zuber denies even this negative connection, arguing that ‘Moltke’s concept of the operation in France in 1914 … had nothing whatsoever to do with the “Schlieffen plan”’. ⁷⁹ He says that the offensive extent of Moltke’s scheme was revealed in his operational order of 5 September 1914, which took up Beseler’s 1900 plan to break the French fortress line by attacking it from the front and the rear. ⁸⁰ But this order was issued five weeks into the war. If we examine Moltke’s original planning we find no affinity with Beseler’s study, ⁸¹ which proposed an advance by 10 or 11 corps on an 80- to 90-kilometre front north of Verdun, keeping at a safe distance from the Belgian fortresses of Liège and Namur. Moltke planned a coup de main against Liège to open a much wider invasion corridor admitting 26 corps organized in five armies. These armies were defined as ‘the main forces’, and their mission was to march ‘through Belgium and Luxembourg to France’. The strongest armies were those on the extreme right, 1st and 2nd with 6 corps each. They were to advance north of the Meuse aiming initially for Brussels, as in the Schlieffen plan. So the Schwerpunkt of the German advance in 1914 was against Brussels–Namur and on into France, not against Rheims–Verdun and onto the rear of the fortress system, as Beseler envisaged. The attack in 1914 was conceived as ‘a wheeling movement’ (‘Schwenkung’), the overall pace of which should be governed by the progress made on the right wing – which means that 4th and 5th Armies, those nearest to Verdun, would be the slowest-moving parts of the phalanx, whereas the Beseler plan said that the success of the attack depended on moving quickly around Verdun and against the rear of the fortress system. ⁸²

Nor did the deployment instructions for 6th and 7th Armies on the German left wing give any hint of a breakthrough attack against the front of the fortified position. The principal task of these armies, with eight corps altogether, was ‘the protection of the left flank of the main forces’. They were enjoined in the first instance to ‘advance against the Moselle below Frouard and the Meurthe … in order to pin down the French forces assembled there and prevent them being transferred to the French left wing’. ⁸³ As in the Schlieffen plan, the German left wing was meant to secure and subserve the main attack through Belgium, not to embark on a major offensive of its own.

So where is Zuber’s evidence for saying that Moltke intended all along to break the French fortress line? He points out that one variant of the original instructions given to the left wing was to transfer elements of 6th Army from the line east of the Meurthe and Moselle to the west bank of the Moselle in front of Metz, and he surmises that the point of this move was probably to break through the French line of fortifications between Toul and Verdun. ⁸⁴ Covering the same ground in a more recent publication, he asserts as a plain fact that 6th Army was ‘to attack west from Metz to break through the French fortress line’. ⁸⁵ But that is a highly inflated reading of the evidence. Moltke’s instruction said that ‘if 6th and 7th Armies do not encounter superior French forces, then parts of 6th Army … could move through or south of Metz to intervene in fighting on the left bank of the Moselle’. ⁸⁶ Zuber apparently understands fighting on the left bank of the Moselle as code for a breakthrough attack on the Meuse forts between Toul and Verdun. But if the intention was to break through the French border position, that should have been attempted precisely where the Germans did ‘not encounter superior French forces’. Zuber would have us believe that 6th Army was to march away from a weakly defended sector of the enemy position in order to launch a breakthrough attack on another sector that might well be much better defended.

That is not very convincing, but there is a logical explanation for the proposed redeployment of ‘parts of 6th Army’ to the front of Metz. If no superior enemy forces were encountered on the Meurthe, that would suggest that enemy strength was being concentrated elsewhere – probably around Verdun in preparation for a thrust at the left flank of the main German forces. Allowance was made for this particular danger in the instructions to 5th Army, which was meant to push its right wing north-west to capture Longwy and Montmédy, while its left wing maintained the connection with Diedenhofen. In the course of this evolution the army would be ‘sharply echeloned to the left’ so that it could turn to face an enemy advance from Verdun: ‘In order to ward off a French counter-attack undertaken with strong forces from the direction of Verdun, the deployment of 5th Army in a position with the front towards the south-west or the south may become necessary at any time.’ ⁸⁷ It was surely in order to help 5th Army repel such an attack that elements of 6th Army could be shifted northwards. That would make sense of the formulation ‘intervene in fighting on the left bank of the Moselle’ (‘das Eingreifen … in Kämpfe auf dem linken Moselufer’), which clearly implies that these forces were to take part in an ongoing engagement, not start a new operation of their own. By joining in 5th Army’s defensive battle, 6th Army would be acting on its duty to protect the left flank of the main German army and engage strong enemy forces that might otherwise stand in the way of the attack through Belgium. Zuber finds no support for his theory in the relevant documentation: there is not the slightest whiff of a breakthrough concept in the original German war plan for 1914.

But that is not quite the end of the matter. Zuber claims that Moltke’s intention of breaking the French fortress line also emerged in his operational instructions of 27 August, where 6th and 7th Armies were given the task of ‘breaking through the “Trouée de Charmes”, but only if the French began a general withdrawal’. ⁸⁸ Zuber does not say what he understands by ‘a general withdrawal’, but it is essential to clarify this point. The Reichsarchiv history of the Great War stated that the ‘breakthrough’ order was to be carried out if the French right wing withdrew to its fortified line (‘Durchbruch … für den Fall, daß der Gegner in die Festungsfront zurückging’). ⁸⁹ But here the Reichsarchiv historians were misreading their own source materials. Moltke’s order said: ‘If the enemy withdraws, then 6th Army … will cross the Moselle and proceed in the general direction of Neufchâteau.’ ⁹⁰ What was meant in this context by a withdrawal of the enemy right wing is made quite clear in the analytical part of the instructions: ‘If this French wing withdraws, then it will try to use the fortress triangle Langres–Dijon–Besançon as a base for continuous flanking attacks from the south against the German armies, or to assemble forces for a new offensive.’ ⁹¹ The enemy withdrawal in question was not, then, a retreat behind the fortress line, but an abandonment of that position in favour of a new base of operations to the south. In that case the advance of 6th Army across the Moselle would not be a breakthrough at all, but quite literally a walkover. The army would simply march through the vacated line between Toul and Epinal and position itself between the enemy’s fortress triangle and the left flank of the main German forces. Moltke did not order a breakthrough attack on 27 August: he merely gave instructions that if the enemy fell back from his border position to his fortress triangle, 6th Army must get to the right place for continuing the role it had from the very start, that of protecting the left flank of the main German forces (‘Der Armee fällt dann der Schutz der linken Flanke des Heeres zu’). ⁹² The responsibility for bringing about a decisive result still lay with the armies attacking west of Verdun, which were exhorted to continue a vigorous pursuit and prevent the retreating enemy from organizing a new defensive front. ⁹³

We do not find a definite intention of breaking the fortress line until we come to Moltke’s operational order of 5 September, directing 4th and 5th Armies to advance on the rear of the position and thereby create the opportunity for 6th and 7th Armies to break through in front. ⁹⁴ But this new approach was clearly a response to the failure of the old one. Moltke explained that ‘the enemy has eluded the enveloping attack of 1st and 2nd Armies, and some of his forces have now established a connection with Paris’. This latter development was a game-changing setback for the Germans. A French position leaning on the fortified capital presented no open flank, so a renewal of the envelopment attack was now impossible. Moltke also noted that the enemy was transferring troops from his right and centre to his left, where they would combine with newly raised units to stiffen the defence of Paris and even ‘threaten the right flank of the German army’. ⁹⁵ The spearhead of the German attack, the supposedly decisive right wing, had mutated quite suddenly into the Achilles heel of the whole operation.

But Moltke had been forewarned of this dilemma. As we have seen, Schlieffen anticipated that the French could block the German advance by forming a continuous front between Paris and Verdun. His argument in the 1905 memorandum was that the Germans could achieve a decisive result only if they were strong enough to outflank that position by marching around the western side of Paris while simultaneously pinning the enemy down all along the front. He gave precise figures for the strength required in that operation: 33 and a half corps, including 25 active corps. ⁹⁶ Moltke’s army along the Paris–Verdun front consisted of 22 corps, only 15 of which were active formations. ⁹⁷ In terms of first-line units with their complement of heavy artillery, he was 10 corps short of what Schlieffen regarded as indispensable for success at this juncture. We could argue that Moltke ought to have strengthened his main front with 2 army corps from the left wing, as the Schlieffen plan requires; but even then he would have approached the line Paris–Verdun with just 24 corps, a force weaker still than the one Schlieffen had said was ‘too weak to continue operations in this direction’. ⁹⁸ Moltke followed the trajectory of the Schlieffen plan, but only up to the point where it was painfully obvious that he would have needed the army of the Schlieffen plan to proceed any further along these lines. Lacking the strength and support to advance across the lower Seine, his right wing became a positive liability, caught in an exposed position to the east of fortress Paris and the new French 6th army assembled there for a counter-attack.

In fairness to Zuber, it could be said that Moltke tried to get out of this quandary by converting to the Beseler plan – except that the Beseler plan did not start with a German right wing hung out under the menacing shadow of Paris. If Moltke wanted to switch the German offensive to the left, he would first have to extricate the right wing from the danger it was in, which is why his new plan had a dual aspect. When he resolved to attack the fortress line, he also ordered 1st and 2nd Armies to break off their advance east of Paris and withdraw to a west-facing position from where they should ‘respond offensively to enemy operations out of Paris’, lending each other ‘mutual support’ as they did so. ⁹⁹ But there was an air of unreality about this order, almost as if Moltke could not bring himself to acknowledge the true extent of the emergency on his right wing. The scale of the Germans’ numerical disadvantage made it illusory to think that 1st and 2nd Armies could act in concert against a French advance from Paris. The German 2nd Army and half of the 3rd, with 134 battalions altogether, were facing 268 enemy battalions. It was surely inconceivable that 2nd Army, already outnumbered two to one in its own sector, could have turned to assist 1st Army in countering the threat from Paris. On any realistic assessment it was Alexander von Kluck’s 1st Army alone, with 128 battalions, which would have to meet the 127 battalions of the French 6th Army, as well as coping with 64 British battalions in front. ¹⁰⁰ Late in the evening of 5 September, Kluck instructed his corps commanders to begin the withdrawal to their defensive alignment with 2nd Army on the following day; but that was the very day when the French 6th Army attacked out of Paris, aiming directly at 1st Army’s right flank. By noon on 7 September, Kluck had committed practically all of his forces to joining in the resultant battle on the Ourcq, causing a famously fateful gap to open between 1st and 2nd Armies. ¹⁰¹

Provocative to the end, Terence Zuber maintains that this crisis could have been averted if 1st Army had carried out the withdrawal to its ‘assigned defensive position’. That would have provided a ‘firm German right flank’, stabilizing the situation on this front and enabling the Germans to concentrate their efforts on the left. Kluck and his chief of staff, Hermann von Kuhl, had ruined Moltke’s new concept by refusing to do what they were told. ¹⁰² But where exactly was the ‘assigned defensive position’ that 1st Army was supposed to occupy? Kluck and Kuhl benefited from a visit to their headquarters by Oberstleutnant Richard Hentsch on 5 September. ¹⁰³ Hentsch was sent by Moltke to clarify the new instructions and explain their urgency, so we may assume that he was acting in full accord with Moltke’s intentions when he approved the withdrawal of 1st Army to a line between Crouy and Joiselle. On the right wing, IInd Army Corps and IVth Reserve Corps were ordered to stand ‘south-west of Crouy’ ¹⁰⁴ – and that is in fact precisely where they were on 6 September. The 1st Army situation report for that day said that IInd Army Corps and IVth Reserve Corps were engaged in ‘heavy fighting south-west of Crouy against strong enemy forces advancing from Paris’. ¹⁰⁵ Kluck’s right wing had in effect taken up its ‘assigned defensive position’, but that did not provide a ‘firm German right flank’. In order to avoid an envelopment of his right flank and, as per his instructions, ‘respond offensively’ to the enemy action, Kluck was obliged to bring up all the reinforcements he could muster from his left, and take the risk of becoming separated from 2nd Army.

There is, then, no counterfactual version of the Marne in which Kluck religiously follows his 5 September orders in every particular and thereby consolidates the German right wing. Even if 1st Army had reached all of its designated positions before the Allies began their counter-attack, the material preconditions for the battle of the Marne would have been no different. It may be true that Moltke had ‘reverted to Beseler’s 1900 plan’, ¹⁰⁶ but he still faced a desperate struggle on the right wing in consequence of his underpowered imitation of Schlieffen’s 1905 plan. The Reichsarchiv considered that he was now engaged in ‘a hopeless attempt to master two quite different tasks with a force that was being pulled apart and was in any case insufficient’. The conclusion, put in suitably Clausewitzian terms, was that ‘the “culminating point” of the German offensive had been overstepped’. ¹⁰⁷ But that was always the most likely outcome. The die was cast long before, when Moltke decided to emulate the Schlieffen plan under circumstances for which it was never intended, and with forces that were, as Schlieffen had demonstrated, wholly inadequate for such an undertaking.

One obvious question remains: Moltke had studied the Schlieffen plan, so why did he pay no heed to Schlieffen’s argument about the number of troops that would be necessary for a decisive attack on France? The answer may perhaps be found in their opposing views of the relation between attack and defence. Echoing Clausewitz once again, Schlieffen maintained that ‘the defensive is the stronger form of war’, ¹⁰⁸ but Moltke was convinced that ‘the stronger form of combat lies in the offensive’ because it represents a ‘striving after positive goals’. He allowed that the offensive spirit could be blunted in a long-drawn-out assault on the French border position, but he thought that an attack ‘in the open’, brought about by an advance through Belgium, would lend the German army ‘the impetus and initiative that we need all the more, the greater the number of enemies we have to contend with’. ¹⁰⁹ Moltke subscribed to a then fashionable belief that the moral advantage of the offensive could make up for a lack of numbers. Unfortunately for the Germans, it was Schlieffen’s Clausewitzian outlook that was vindicated at the battle of the Marne.