Treaty of London recognised Belgium as an independent and neutral state. Until 1911, Belgian strategic analysis anticipated that if war came, the Germans would attack France across the Franco-German border and trap the French armies against the Belgian frontier, as they had done in 1870. British and French guarantees of Belgian independence were made before 1914 but the possibility of landings in Antwerp was floated by the British military attaché in 1906 and 1911, which led the Belgians to suspect that the British had come to see Belgian neutrality as a matter of British diplomatic and military advantage, rather than as an end in itself. The
Agadir Crisis (1911) left the Belgian government in little doubt as to the risk of a European war and an invasion of Belgium by Germany. In September 1911, a government meeting concluded that Belgium must be prepared to resist a German invasion, to avoid accusations of collusion by the British and French governments. Britain, France and the Netherlands were also to continue to be treated as potential enemies. In 1913 and 1914, the Germans made inquires to the Belgian military attaché in Berlin, about the passage of German military forces through Belgium. If invaded, Belgium would need foreign help but would not treat foreign powers as allies or form objectives beyond the maintenance of Belgian independence. Neutrality forced the Belgian government into a strategy of military independence, based on a rearmament programme begun in 1909, which was expected to be complete in 1926. The Belgian plan was to have three army corps, to reduce the numerical advantage of the German armies over the French, intended to deter a German invasion.
Conscription began in 1909 but with a reduction in the term of service to fifteen months; the Agadir Crisis made the government continue its preparations but until 1913 the size of the army was not fixed as a proportion of the population. The annual conscription of 13,300 recruits was increased to 33,000 so that a field army of 180,000 men could be attained. Older men would continue to serve as garrison troops and by 1926 340,000 men would be available. Implementation of the new scheme had disrupted the old one but had not become effective by 1914. During the crisis over the assassination of
Archduke Franz Ferdinand of Austria, regiments were divided and eight conscription classes were incorporated into the army, to provide 117,000 men for the field army and 200,000 fortress troops. The Belgian army planned all-round defence, rather than concentrating the army against a particular threat. Belgian defences were to be based on a National Redoubt at Antwerp, with the field army massed in the centre of the country 60 kilometres (37 mi) from the border, ready to manoeuvre to delay an invasion, while the frontiers were protected by the fortified regions of Liège and Namur. The German invasion of Belgium on 4 August 1914, in violation of Article VII of the Treaty of London, was
the reason given by the British government for declaring war on Germany.
Belgian defensive plans
Belgian military planning was based on the assumption that other powers would eject an invader but the likelihood of a German invasion did not lead to France and Britain being seen as allies or for the Belgian government to do more than protect its independence. The
Anglo-French Entente (1904) had led the Belgians to perceive that the British attitude to Belgium had changed and that it was now seen as a protectorate. A Belgian General Staff was formed in 1910 but the Chef d'État-Major Général de l'Armée, Lieutenant-Général Harry Jungbluth was retired on 30 June 1912 and not replaced until May 1914 by Lieutenant-General Chevalier de Selliers de Moranville. Moranville began planning for the concentration of the army and met railway officials on 29 July. Belgian troops were to be massed in central Belgium, in front of the
National redoubt of Belgium ready to face any border, while the
Fortified Position of Liège and
Fortified Position of Namur were left to secure the frontiers. On mobilisation, the King became Commander-in-Chief and chose where the army was to concentrate. Amid the disruption of the new rearmament plan the disorganised and poorly trained Belgian conscripts would benefit from a central position to delay contact with an invader. The army would also need fortifications for defence but these had been built on the frontier. Another school of thought wanted a return to a frontier deployment, in line with French theories of the offensive. The Belgian plan that emerged was a compromise in which the field army concentrated behind the Gete river with two divisions forward at Liège and Namur.
Germany: Schlieffen–Moltke Plan
German strategy had given priority to offensive operations against France and a defensive posture against Russia since 1891. German planning was determined by numerical inferiority, the speed of mobilisation and concentration and the effect of the vast increase of the power of modern weapons. Frontal attacks were expected to be costly and protracted, leading to limited success, particularly after the French and Russians modernised their fortifications on the frontiers with Germany.
Alfred von Schlieffen, Chief of the
German General Staff (
Oberste Heeresleitung, OHL) from 1891 to 1906 devised a plan to evade the French frontier fortifications, with an offensive on the northern flank, which would have a local numerical superiority and obtain rapidly a decisive victory. By 1898–1899, such a manoeuvre was intended to swiftly pass between Antwerp and Namur and threaten Paris from the north.
Eastern Front to 26 September 1914
Helmuth von Moltke the Younger succeeded Schlieffen in 1906 and was less certain that the French would conform to German assumptions. Moltke adapted the deployment and concentration plan to accommodate an attack in the centre or an enveloping attack from both flanks as variants, by adding divisions to the left flank opposite the French frontier, from the c. 1,700,000 men expected to be mobilised in the Westheer (Western Army). The main German force would still advance through Belgium and attack southwards into France, the French armies would be enveloped on the left and pressed back over the Meuse, Aisne, Somme, Oise, Marne and Seine, by short, rapid attacks, unable to withdraw into central France. The French would either be annihilated or the manoeuvre from the north would create conditions for victory in the centre or in Lorraine, on the common border.
A corollary to the emphasis on the Western Front was a lack of troops for the
Eastern Front against Russia. In the east the Germans planned a defensive strategy and relied on the
Austro-Hungarian Army (Landstreitkräfte Österreich-Ungarns/Császári és Királyi Hadsereg) to divert the Russians from East Prussia, while France was crushed. Divisions from the German army in the west (Westheer) would be redeployed to the East to deal with the Russians as soon as a breathing-space was gained against the French.
France: Plan XVII
, King of the Belgians; Albert became king in 1909 and commanded the Belgian army throughout World War I
Under Plan XVII the French peacetime army was to form five field armies, with a group of reserve divisions attached to each army and a group of reserve divisions on each flank, a military force of c. 2,000,000 men. The armies were to concentrate opposite the German frontier around Épinal, Nancy and Verdun–Mezières, with an army in reserve around Ste. Ménéhould and Commercy. Since 1871, railway building had given the French General Staff sixteen lines to the German frontier, against thirteen available to the German army and the French could afford to wait until German intentions were clear. The French deployment was intended to be ready for a German offensive in Lorraine or through Belgium. It was anticipated that the Germans would use reserve troops but also expected that a large German army would be mobilised on the border with Russia, leaving the western army with sufficient troops only to advance through Belgium south of the Meuse and the Sambre rivers. French intelligence had obtained a 1905 map exercise of the German general staff, in which German troops had gone no further north than Namur and assumed that plans to besiege Belgian forts were a defensive measure against the Belgian army.
A German attack from south-eastern Belgium towards Mézières and a possible offensive from Lorraine towards Verdun, Nancy and St. Dié was anticipated; the plan was an evolution from Plan XVI and made more provision for the possibility of a German offensive from the north through Belgium. The First, Second and Third armies were to concentrate between Épinal and Verdun opposite Alsace and Lorraine, the Fifth Army was to assemble from Montmédy to Sedan and Mézières and the Fourth Army was to be held back west of Verdun, ready to move east to attack the southern flank of a German invasion through Belgium or southwards against the northern flank of an attack through Lorraine. No formal provision was made for combined operations with the
British Expeditionary Force (BEF) but joint arrangements had been made and in 1911 during the
Second Moroccan Crisis, the French had been told that six British divisions could be expected to operate around Maubeuge.