World War I: Battle of Mons

British forces before the Battle of Mons
British forces rest before the Battle of Mons. Photograph Source: Public Domain

The Battle of Mons was fought August 23, 1914, during World War I (1914-1918) and was the British Army's first engagement of the conflict. Operating at the extreme left of the Allied line, the British assumed a position near Mons, Belgium in an attempt to stop the German advance in that area. Attacked by the German First Army, the outnumbered British Expeditionary Force mounted a tenacious defense and inflicted heavy losses on the enemy. Largely holding through the day, the British finally fell back due to increasing German numbers and the retreat of the French Fifth Army on their right.


Crossing the Channel in the early days of World War I, the British Expeditionary Force deployed in the fields of Belgium. Led by Field Marshal Sir John French, it moved into position in front of Mons and formed a line along the Mons-Condé Canal, just to the left of the French Fifth Army as the larger Battle of the Frontiers was getting underway. A fully professional force, the BEF dug in to await the advancing Germans who were sweeping through Belgium in accordance to the Schlieffen Plan (Map).

Comprised of four infantry divisions, a cavalry division, and a cavalry brigade, the BEF possessed around 80,000 men. Highly trained, the average British infantryman could hit a target at 300 yards fifteen times a minute. Additionally, many of the British troops possessed combat experience due to service across the empire. Despite these attributes, German Kaiser Wilhelm II allegedly dubbed the BEF a "contemptible little army" and instructed his commanders to "exterminate" it. The intended slur was embraced by the members of the BEF who began to refer themselves as the "Old Contemptibles".

Armies & Commanders


  • Field Marshal Sir John French
  • 4 divisions (approx. 80,000 men)


  • General Alexander von Kluck
  • 8 divisions (approx. 150,000 men)

First Contact

On August 22, after being defeated by the Germans, the commander of the Fifth Army, General Charles Lanrezac, asked French to hold his position along the canal for 24 hours while the French fell back. Agreeing, French instructed his two corps commanders, General Douglas Haig and General Horace Smith-Dorrien to prepare for the German onslaught. This saw Smith-Dorrien's II Corps on the left establish a strong position along the canal while Haig's I Corps on the right formed a line along the canal which also bent south along the Mons–Beaumont road to protect the BEF's right flank. French felt this was necessary in case Lanrezac's position to the east collapsed. A central feature in the British position was a loop in the canal between Mons and Nimy which formed a salient in the line.

That same day, around 6:30 AM, the lead elements of General Alexander von Kluck's First Army began making contact with the British. The first skirmish occurred in the village of Casteau when C Squadron of the 4th Royal Irish Dragoon Guards encountered men from the German 2nd Kuirassiers. This fight saw Captain Charles B. Hornby use his saber to become the first British soldier to kill an enemy while Drummer Edward Thomas reportedly fired the first British shots of the war. Driving the Germans off, the British returned to their lines (Map).

The British Hold

At 5:30 AM on August 23, French again met with Haig and Smith-Dorrien and told them to strengthen the line along the canal and to prepare the canal bridges for demolition. In the early morning mist and rain, the Germans began appearing on the BEF's 20-mile front in increasing numbers. Shortly before 9:00 AM, German guns were in position north of the canal and opened fire on the BEF's positions. This was followed by an eight-battalion assault by infantry from IX Korps. Approaching the British lines between Obourg and Nimy, this attack was met by heavy fire form the BEF's veteran infantry. Special attention was paid to the salient formed by the loop in the canal as the Germans attempted to cross four bridges in the area.

Decimating the German ranks, the British maintained a such a high rate of fire with their Lee-Enfield rifles that the attackers believed they were facing machine guns. As von Kluck's men arrived in greater numbers, the attacks intensified forcing the British to consider falling back. On the north edge of Mons, a bitter fight continued between the Germans and the 4th Battalion, Royal Fusiliers around a swing bridge. Left open by the British, the Germans were able to cross when Private August Neiemeier jumped in the canal and closed the bridge.


By afternoon, French was forced to order his men to begin falling back due to heavy pressure on his front and the appearance of the German 17th Division on his right flank. Around 3:00 PM, the salient and Mons were abandoned and elements of the BEF became engaged in rearguard actions along the line. In one situation a battalion of the Royal Munster Fusiliers held off nine German battalions and secured the safe withdrawal of their division. As night fell, the Germans halted their assault to reform their lines.

Though the BEF established new lines a short distance south, word arrived around 2:00 AM on August 24 that the French Fifth Army was in retreat to the east. With his flank exposed, French ordered a retreat south into France with the goal of establishing at line along the Valenciennes–Maubeuge road. Reaching this point after a series of sharp rearguard actions on the 24th, the British found that the French were still retreating. Left little choice, the BEF continued to move south as part of what became known as the Great Retreat (Map).


The Battle of Mons cost the British around 1,600 killed and wounded, including later WWII hero Bernard Montgomery. For the Germans, the capture of Mons proved costly as their losses numbered around 5,000 killed and wounded. Though a defeat, the stand of the BEF bought valuable time for Belgian and French forces to fall back in an attempt to form a new defensive line. The BEF's retreat ultimately lasted 14 days and ended near Paris (Map). The withdrawal ended with the Allied victory at the First Battle of the Marne in early September.

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Hickman, Kennedy. "World War I: Battle of Mons." ThoughtCo, Jul. 31, 2021, Hickman, Kennedy. (2021, July 31). World War I: Battle of Mons. Retrieved from Hickman, Kennedy. "World War I: Battle of Mons." ThoughtCo. (accessed June 8, 2023).