World War I: Battle of the Frontiers

Marshal Joseph Joffre during World War I
Marshal Joseph Joffre. Photograph Source: Public Domain

The Battle of the Frontiers was a series of engagements fought from August 7 to September 13, 1914, during the opening weeks of World War I (1914-1918).

Armies & Commanders:


  • General Joseph Joffre
  • Field Marshal Sir John French
  • King Albert I
  • 1,437,000 men


  • Generaloberst Helmuth von Moltke
  • 1,300,000 men


With the beginning of World War I, the armies of Europe began mobilizing and moving towards the front according to highly detailed timetables. In Germany, the army prepared to implement a modified version of the Schlieffen Plan. Created by Count Alfred von Schlieffen in 1905, the plan was a response to Germany's likely need to fight a two-front war against France and Russia. After their easy victory over the French in the 1870 Franco-Prussian War, Germany viewed France as less of a concern than its larger neighbor to the east. As a result, Schlieffen elected to mass the bulk of Germany's military might against France with the goal of winning a quick victory before the Russians could fully mobilize their army. With France out of the war, Germany would be free to focus their attention on the east (Map).

Anticipating that France would strike across the border into Alsace and Lorraine, which had been lost during the earlier conflict, the Germans planned to violate the neutrality of Luxembourg and Belgium to attack the French from the north in a massive battle of encirclement. German troops were to hold along the border while the right wing of the army swung through Belgium and past Paris in an effort to destroy the French army. In 1906, the plan was adjusted by Chief of the General Staff, Helmuth von Moltke the Younger, who weakened the critical right wing to reinforce Alsace, Lorraine, and the Eastern Front.

French War Plans

In the years before the war, General Joseph Joffre, Chief of the French General Staff, sought to update his nation's war plans for a potential conflict with Germany. Though he originally desired to design a plan that had French troops attack through Belgium, he was later unwilling to violate that nation's neutrality. Instead, Joffre and his staff developed Plan XVII which called for French troops to concentrate along the German border and commence attacks through the Ardennes and into Lorraine. As Germany possessed a numerical advantage, the success of Plan XVII was based on them sending at least twenty divisions to the Eastern Front as well as not immediately activating their reserves. Though the threat of an attack through Belgium was acknowledged, French planners did not believe the Germans to have sufficient manpower to advance west of the Meuse River. Unfortunately for the French, the Germans gambled on Russia mobilizing slowly and devoted the bulk of their strength to the west as well as immediately activated their reserves.

Fighting Begins

With the start of the war, the Germans deployed the First through Seventh Armies, north to south, to implement the Schlieffen Plan. Entering Belgium on August 3, First and Second Armies pushed back the small Belgian Army but were slowed by the need to reduce the fortress city of Liege. Though the Germans started to bypass the city, it took until August 16 to eliminate the last fort. Occupying the country, the Germans, paranoid about guerrilla warfare, killed thousands of innocent Belgians as well as burned several towns and cultural treasures such as the library at Louvain. Dubbed the "rape of Belgium," these actions were needless and served to blacken Germany's reputation abroad. Receiving reports of German activity in Belgium, General Charles Lanrezac, commanding the Fifth Army, warned Joffre that the enemy was moving in unexpected strength. 

French Actions

Implementing Plan XVII, VII Corps from the French First Army entered Alsace on August 7 and captured Mulhouse. Counterattacking two days later, the Germans were able to reclaim the town. On August 8, Joffre issued General Instructions No. 1 to the First and Second Armies on his right. This called for an advance northeast into Alsace and Lorraine on August 14. During this time, he continued to discount reports of enemy movements in Belgium. Attacking, the French were opposed by the German Sixth and Seventh Armies. As per Moltke's plans, these formations conducted a fighting withdrawal back to a line between Morhange and Sarrebourg. Having obtained additional forces, Crown Prince Rupprecht launched a converging counterattack against the French on August 20. In three days of fighting, the French withdrew to a defensive line near Nancy and behind the Meurthe River (Map).    

Further north, Joffre had intended to mount an offensive with the Third, Fourth, and Fifth Armies but these plans were overtaken by events in Belgium. On August 15, after urging from Lanrezac, he ordered Fifth Army north into the angle formed by the Sambre and Meuse Rivers. To fill the line, the Third Army slid north and the newly-activated Army of Lorraine took its place. Seeking to gain the initiative, Joffre directed Third and Fourth Armies to advance through the Ardennes against Arlon and Neufchateau. Moving out on August 21, they encountered the German Fourth and Fifth Armies and were badly beaten. Though Joffre attempted to restart the offensive, his battered forces were back at their original lines by the night of the 23rd. As the situation along the front developed, Field Marshal Sir John French's British Expeditionary Force (BEF) landed and began concentrating at Le Cateau. Communicating with the British commander, Joffre asked French to cooperate with Lanrezac on the left.


Having occupied a line along the Sambre and Meuse Rivers near Charleroi, Lanrezac received orders from Joffre on August 18 instructing him to attack either north or east depending on the enemy's location. As his cavalry was unable to penetrate the German cavalry screen, Fifth Army held its location. Three days later, having realized that the enemy was west of the Meuse in force, Joffre directed Lanrezac to strike when an "opportune" moment arrived and arranged for support from the BEF. Despite these orders, Lanrezac assumed a defensive position behind the rivers. Later that day, he came under attack from General Karl von Bülow's Second Army (Map). 

Able to cross the Sambre, German forces succeeded in turning back French counterattacks on the morning of August 22. Seeking to gain an advantage, Lanrezac withdrew General Franchet d'Esperey's I Corps from the Meuse with the goal of using it to turn Bülow's left flank. As d'Esperey moved to strike on August 23, Fifth Army's flank was threatened by elements of General Freiherr von Hausen's Third Army which had begun crossing the Meuse to the east. Counter-marching, I Corps was able to block Hausen, but could not push Third Army back over the river. That night, with the British under heavy pressure on his left and a grim outlook on his front, Lanrezac decided to retreat south.


As Bülow pressed his attack against Lanrezac on August 23, he requested General Alexander von Kluck, whose First Army was advancing on his right, to attack southeast into the French flank. Moving forward, First Army encountered French's BEF which had assumed a strong defensive position at Mons. Fighting from prepared positions and employing rapid, accurate rifle fire, the British inflicted heavy losses on the Germans. Repelling the enemy until evening, French was compelled to pull back when Lanrezac departed leaving his right flank vulnerable. Though a defeat, the British bought time for the French and Belgians to form a new defensive line.


In the wake of the defeats at Charleroi and Mons, French and British forces began a long, fighting withdrawal south towards Paris. Retreating, holding actions or unsuccessful counterattacks were fought at Le Cateau (August 26-27) and St. Quentin (August 29-30), while Mauberge capitulated September 7 after a short siege. Forming a line behind the Marne River, Joffre prepared to make a stand to defend Paris. Increasingly irate by the French habit of retreating without informing him, French wished to pull the BEF back towards the coast, but was convinced to stay at the front by War Secretary Horatio H. Kitchener (Map).

The opening actions of the conflict had proved a disaster for the Allies with the French suffering around 329,000 casualties in August. German losses in the same period totaled approximately 206,500. Stabilizing the situation, Joffre opened the First Battle of the Marne on September 6 when a gap was found between Kluck and Bülow's armies. Exploiting this, both formations were soon threatened with destruction. In these circumstances, Moltke suffered a nervous breakdown. His subordinates assumed command and ordered a general retreat to the Aisne River. Fighting continued as the fall progressed with the Allies assaulting the Aisne River line before both commenced a race north to the sea. As this concluded in mid-October, heavy combat began again with the start of the First Battle of Ypres.   

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Your Citation
Hickman, Kennedy. "World War I: Battle of the Frontiers." ThoughtCo, Apr. 5, 2023, Hickman, Kennedy. (2023, April 5). World War I: Battle of the Frontiers. Retrieved from Hickman, Kennedy. "World War I: Battle of the Frontiers." ThoughtCo. (accessed June 6, 2023).