The Battle of the Frontiers of France refers to a series of four separate battles, stretching from the Swiss frontier to Mons in Belgium, each of which saw German armies achieve their main objectives (First World War). It marks the period when the German armies advancing through Belgium emerged at the French borders and began to force the French to retreat back towards Paris and the Marne.
The battle was fought on a massive scale. Both the French and Germans committed well over 1,000,000 men, in five French and seven German armies. In comparison the British Expeditionary Force was tiny – only 70,000 strong – although the professionalism of the British regulars increased their effectiveness somewhat. The overall Battle of the Frontiers of France was made up of four separate battles – part of the Battle of Lorraine (14 August-7 September), the Battle of the Ardennes (20-25 August), the Battle of the Sambre or Charleroi (22-23 August) and the Battle of Mons (23 August).
The opening phase of the war saw the Germans invade Belgium and Luxembourg and the French attack Alsace-Lorraine (Battle of Lorraine, 14 August-7 September). This saw two French armies advance almost unopposed into Alsace-Lorraine while their German opponents retreated to the east, waiting for the right moment to launch their counterattack. That moment came on 20 August. The German counterattack forced the French First and Second Armies to retreat back to their starting point, which they reached by 23 August.
Like the Battle of Lorraine, the Battle of the Ardennes (20-25 August) began with a French offensive which it was hoped would outflank the German armies advancing through Belgium. However, this time the advancing French troops collided head on with advancing German troops, making up the hinge of the German advance through Belgium. The French advance was stopped and then the two French armies forced into a retreat, at first to the Meuse and then to a line running south west from Verdun.
The third of the battles of the Frontiers – the Battle of the Sambre or Charleroi, was in many ways the most important. It was fought between the French Fifth Army of General Charles Lanrezac and the German Second and Third Armies (General Karl von Bulow and General Max von Hausen). Lanrezac had been worried about a potential German advance through Belgium for some time, but General Joffre remained convinced that the main attack would come further south. His Fifth Army had been posted at the northern end of the French line, but not far enough north for his comfort. Finally, as news of the German advance into Belgium reached French headquarters, Joffre ordered Lanrezac to move north to defend the line of the Sambre River.
On 21 August the first German troops reached the river, and found several undefended bridges across the river. French information on the river had been woefully inaccurate; failing to give a true indication even of how many bridges existed. On 21 August German troops crossed the Sambre at two locations. This was not necessarily a crisis, but on 22 August Lanrezac ordered a counterattack which ended in failure. On the next day the Germans attacked on the French right, crossing the Meuse near its junction with the Sambre. A gap had developed between the French Fifth Army and the Fourth, retreating after defeat in the Ardennes. At 11.00 pm on 23 August Lanrezac was forced to order a general retreat.
The Battle of Mons (23 August) was essentially part of the wider fighting on the Sambre. In the aftermath of their setbacks on 22 August the French asked Sir John French to launch a counterattack on what was believed to the right flank of the German armies. Instead French agreed to hold the line of the Mons canal for 24 hours. This was a wise choice – the German line was actually much longer that the French believed, extending past the British position at Mons. The German First Army under General Alexander von Kluck was heading straight for the British positions. On 23 August the four British infantry divisions were attacked by at least six of von Kluck’s fourteen divisions.
The British were badly outnumbered, but the BEF was a fully professional army. The British regulars were trained to fire fifteen aimed shots per minute. At Mons the accuracy and speed of the British rifle fire convinced many Germans that they were facing massed machine guns. The British regulars were also the only troops on the western front to be at least the equals of the Germans at digging trenches. Much of this expertise had been earned at high cost in the Boer War, where British regulars had suffered heavy casualties attacking entrenched Boer riflemen.
At the end of the day the British had suffered 1,600 casualties, most in II Corps. The line along the Mons canal had been held, but to the east the French had been forced to retreat. On the morning of 24 August, Sir John French was forced to order a retreat.
The Battle of the Frontiers of France was a decisive German victory. By the time it ended the French strategy of an attack into Germany had been defeated, while the German armies advancing through Belgium had swept aside all resistance along the Franco-Belgium border and were ready to begin the advance south and south west towards Paris. Over the next two weeks the British and French would be forced into a retreat that would only stop at the Marne. Both the French and Germans lost over 300,000 men in the battle making it one of the most expensive of the war.
Despite its size and cost, the Battle of the Frontiers of France did not have a significant impact on the course of the war. A French victory on the Sambre might have stalled the entire plan, but the German victory left the most dangerous part of the German plan – the sweep around Paris – still to come. This was the part of his plan that had most worried Schlieffen. The German plan was designed to envelop and destroy the French armies. The right wing of the German advance would somehow have to get past Paris to achieve this, but whichever side of the city was chosen would allow the French to attack an exposed flank. In the event, von Kluck’s army would pass to the east of Paris, but still fail to maintain contact with the Second Army, creating a gap that would be exploited by Joffre during the Battle of the Marne.