[Ennath]

August 21, 1914
Battle of Charleroi

France's pre-war strategy document, Plan XVII, called for French 5th Army to join 3rd and 4th Armies in an invasion of Germany through the Ardennes. This however assumed that Germany would not attempt an invasion of Belgium further north. Whilst Charles Lanrezac, 5th Army commander, believed this a distinct possibility, particularly as he observed a massive build-up of German forces, Joseph Joffre, the French Commander-in-Chief, refused to consider the possibility. Joffre did however allow Lanrezac to extend his lines northwest to the Sambre on August 12, but at the same time Lanrezac lost some of his troops, transferred to the Ardennes offensive; they were replaced by a corps from the 2nd Army in Lorraine. On August 15, after lobbying from Lanrezac, Joffre directed 5th Army north into the angle formed by the Sambre and Meuse Rivers.

Hoping to gain the initiative, Joffre ordered 3rd and 4th Armies to attack through the Ardennes against Arlon and Neufchateau. Advancing on August 21, they encountered the German 4th and 5th Armies and were badly defeated. As the situation along the front developed, Field Marshal Sir John French's British Expeditionary Force (BEF) disembarked and began assembling at Le Cateau. Communicating with the British commander, Joffre requested that French to cooperate with Lanrezac on the left. Responding to Joffre's order to move north, Lanrezac positioned 5th Army south of the Sambre extending from the Belgian fortress city of Namur to just past the mid-size industrial town of Charleroi in the west. His I Corps, led by Louis Franchet d'Esperey, extended the right south behind the Meuse. To his left, the cavalry corps of Jean-Francois André Sordet linked 5th Army to the BEF.

On August 18, Lanrezac received additional instructions from Joffre directing him to attack north or east depending upon the enemy's location. Seeking to locate Karl von Bülow's 2nd Army, Lanrezac's cavalry moved north of the Sambre but were unable to penetrate the German cavalry screen. Early on August 21, Joffre, increasingly aware of the size of German forces in Belgium, directed Lanrezac to attack when "opportune" and arranged for the BEF to provide support. In authorizing an attack across the river, Joffre expected the German forces to comprise no more than 18 divisions, against which would be ranged Lanrezac's 15, with reinforcements from the BEF adding another 3. Lanrezac, however, believed the German strength to be much higher, nearer in fact to the real figure of 38 divisions. Consequently, on August 21, he asked for a postponement of the attack, preferring to wait for the arrival of the British.

Lanrezac adopted a defensive position behind the Sambre but failed to establish heavily-defended bridgeheads north the river. Additionally, due to poor intelligence regarding the bridges, several were left completely undefended. Attacked later in the day by the lead elements of Bülow's army, the French were pushed back over the river. Though ultimately held, the Germans were able to establish positions on the south bank, successfully defending 2 bridgeheads against repeated French counterattacks. Thousands of Belgians fled from Charleroi and nearby villages.

Bülow assessed the situation and requested that Klemens von Haussen's 3d Army, operating to the east, join in the attack on Lanrezac with the goal of executing a pincer. Haussen agreed to strike west the next day. On the morning of August 22, Lanrezac's corps commanders, on their own initiative, launched attacks north in an effort to throw the Germans back over the Sambre. These proved unsuccessful as 9 French divisions were unable to dislodge 3 German divisions. The failure of these attacks cost Lanrezac high ground in the area while a gap between his army and 4th Army began to open on his right.

Responding, Bülow renewed his drive south with 3 corps without waiting for Haussen to arrive. The center of the French lines, at Charleroi, suffered heavy losses and retreated, whereas the French corps west of Charleroi held its position, as did Franchet d'Esperey's corps in the east. On the 23rd, Bülow managed to cross the Meuse but he chose not to threaten 5th Army's rear in the south, instead ordering a full frontal attack against the French right. Recognizing the dire threat, Franchet counter-marched his men towards their old positions. Engaging Hausen's troops, I Corps checked their advance but could not push them back across the river. He did, however, secure the line of retreat.

Lanrezac, having difficulty communicating with Franchet, expected the lines of retreat to be closed at any moment. Whilst aware that Haussen’s German 3rd Army had established a bridgehead across the Meuse to his south, he did not know that Charles Mangin's brigade had successfully held them back and was on the verge of a successful counterattack. Once news of the Belgian pull-out from Namur reached him, along with the retreat of French 4th Army from the Ardennes, Lanrezac ordered a general withdrawal. Sordet's cavalry, which had reached a state of exhaustion, needed to be withdrawn. This opened a 10-mile gap between Lanrezac's left and the British.

Further west, French's BEF had fought the Battle of Mons. French had ordered his men to begin falling back. This exposed Lanrezac's army to greater pressure on both flanks. Seeing little alternative, he began making plans to withdraw south. These were quickly approved by Joffre. In the fighting around Charleroi, the Germans sustained around 11,000 casualties while the French incurred approximately 30,000.

Lanrezac's decision to withdraw probably saved the French Army from destruction By retreating the French were able to hold northern France, but the French public at large - and Joffre - saw Lanrezac's action as simply lacking “offensive spirit”. Given that Joffre had permitted the withdrawal his subsequent condemnation of Lanrezac - he blamed him for the failure of Plan XVII - looks opportunistic.