The Battle of the Ardennes took place during the First World War fought on the frontiers of France, Germany, Belgium and Luxembourg from 21 to 23 August 1914.

Amid the disruption of the new rearmament plan the disorganised and poorly trained Belgian soldiers would benefit from a central position to delay contact with an invader but it would also need fortifications for defence, which were on the frontier.

Belgian plans became a compromise in which the field army concentrated behind the river Gete with two divisions forward at Liège and Namur.

[1] Field marshal Alfred Graf von Schlieffen was Chief of the German General Staff (Oberste Heeresleitung, OHL) from 1891 until his retirement in 1906.

[a] A student of Carl von Clausewitz, like other Prussian officers, he had been taught that "the heart of France lies between Paris and Brussels".

The Germans expected frontal attacks to be costly and protracted, leading to limited success, particularly after the French and Russians modernised the fortifications on their frontiers with Germany.

Moltke adapted the deployment and concentration plan to accommodate an attack in the centre or an enveloping attack from both flanks as variants to the plan, 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 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.

France had a population and birth rate smaller than those of Germany and invented the concept of élan vital and decided on a strategy of "offensive to the limit", making the will to fight the cornerstone of French military planning.

Colonel Louis Loyzeau de Grandmaison, took up Foch's doctrine and delivered two speeches before the École Militaire that set the foundations of Plan XVII, which was formally adopted in May 1913.

By 20 August, however, it was becoming clear, first to the Fifth Army (General Charles Lanrezac) and then to Commander-in-Chief Joseph Joffre, that a large German force was gathering in the area.

On 22 August in the Third army area, V Corps attacked dug-in German troops at Longwy at 5:00 a.m. in thick fog and heavy rain, with no artillery support.

To the north the IV Corps also advanced in fog, encountered German troops dug in near Virton and was forced back also with a division routed.

[16] Charbonneau explained that the defeat of the Colonial Corps was caused by faulty reconnaissance, the ineffectiveness of advanced guards in causing delay to advancing German units and that French offensive tactics neglected the importance of obtaining a superiority of fire, which had led to reckless attacks.

[17] At Neufchâteau, the French colonial infantry had been out-gunned and outnumbered by German units, which had been able to engage all their forces quickly.

Both sides had attempted to gain fire superiority before advancing and once this had been achieved by the Germans, they had been able to manoeuvre without severe casualties.

[18] The French commanders were ordered by Joffre to continue the offensive on 23 August as early as possible, since his strategy depended on the success of the Third and Fourth armies.

Ruffey replied in the morning that the attack could not begin until his divisions had reorganised and in the early afternoon found that the Germans had forestalled another advance, by pushing the V Corps in the centre back for 5.0 mi (8 km), which led to the rest of the army falling back level.

The 5th Colonial Brigade withdrew from Neufchâteau before dawn on 23 August, exposing the right flank of XII Corps, which also fell back.

By the end of 23 August, the survivors of the Third and Fourth armies were back to their jumping-off positions except for the XI and IX corps on the northern flank.