The Schlieffen Plan and the Battle of the Marne
The Strategic Problem
Germany’s strategic problem after 1894 was simple to state and almost impossible to solve. The Franco-Russian Alliance meant that any war with one would mean war with both. Germany would have to fight on two fronts — against France in the west and Russia in the east — with one army. Russia’s vast territory and slow railways meant it would take roughly six weeks to fully mobilise. France, sitting next door, could mobilise within days. From these facts, Chief of the General Staff Alfred von Schlieffen drew a single conclusion: knock France out fast, then turn east before Russia is ready.
The Schlieffen Plan, drafted by Alfred von Schlieffen between 1891 and 1906, aimed to defeat France within six weeks by invading through neutral Belgium and encircling Paris from the west — before turning east to face the slower-mobilising Russian army.
The Plan in Outline
Schlieffen’s 1905 design called for the bulk of the German army — roughly seven-eighths of available strength — to mass on the right wing in the north, sweep through Belgium and the Netherlands, pivot south through northern France, and encircle Paris from the west. A small left wing would hold the French along the German border in Alsace-Lorraine, even pulling back to draw the French into a trap. The whole operation was timetabled to within days. Russia would still be mobilising; France would have collapsed; Germany would then transfer troops east on its excellent railways. The plan was an act of strategic boldness: it required the violation of Belgian and Dutch neutrality, the assumption that France would attack into the trap on the German border, and the gamble that Russia would not surprise everyone by mobilising faster than expected.
Schlieffen retired in 1906 and died in 1913. His successor as Chief of the General Staff, Helmuth von Moltke (the Younger), modified the plan in important ways. He dropped the violation of Dutch neutrality (concentrating the invasion on Belgium alone), strengthened the left wing in Alsace-Lorraine and weakened the critical right wing. He also redirected some forces east in case of early Russian pressure. Schlieffen on his deathbed reportedly urged: ‘Keep the right wing strong.’ Moltke’s changes have been blamed by some historians (including Gerhard Ritter) for the plan’s failure; others argue Moltke was responding sensibly to changed circumstances. Either way, the German army that marched in August 1914 was not exactly Schlieffen’s.
August 1914: Belgium and the BEF
German troops crossed into Belgium on 4 August 1914. Belgian neutrality had been guaranteed by the 1839 Treaty of London, signed by all the Great Powers including Prussia. Britain had warned that violating Belgian neutrality would mean war; Bethmann-Hollweg dismissed the treaty as a ‘scrap of paper’. Belgium was small but its forts at Liège held out longer than expected, slowing the German advance by perhaps four critical days. Meanwhile the British Expeditionary Force — the BEF, around 100,000 well-trained regulars — crossed the Channel and met the German advance at Mons on 23 August. The BEF inflicted heavy casualties before being forced to retreat. The professional accuracy of British rifle fire so impressed the Germans that some assumed they were facing machine guns.
The Battle of the Marne, 5-12 September 1914
By early September German armies were within 50 km of Paris. The French government had fled to Bordeaux. But the German advance had over-extended itself. The right wing was weakened, troops were exhausted from forced marches, and supply lines were stretched. On 5 September French commander General Joseph Joffre launched a massive counter-attack along the Marne river. The Germans were exposed at a critical gap between their First and Second Armies. French and British forces drove into the gap. Famously, around 6,000 reinforcements were rushed to the front from Paris in a fleet of around 600 commandeered Parisian taxis — a small contribution but a powerful symbol of national mobilisation.
By 12 September the German army had been forced to retreat north to the Aisne river. Moltke suffered a nervous collapse and was sacked. He is reported to have told the Kaiser that the war was lost, though the fighting would in fact continue for another four years. The retreat ended the Schlieffen timetable. France had not collapsed in six weeks. Russia was already attacking in East Prussia. The Germans now faced exactly the two-front war the plan had been designed to avoid.
From mid-September each side tried to outflank the other to the north — the so-called ‘race to the sea’. By the First Battle of Ypres in late October 1914 both armies had reached the English Channel. There was nowhere left to manoeuvre. Both sides dug in. By late November the Western Front had become a continuous line of trenches running roughly 700 km from the Channel coast to the Swiss border. Movement gave way to siege. The war that was supposed to be over by Christmas would last another four years. The failure of the Schlieffen Plan therefore did not just cost Germany the campaign of 1914 — it produced the strategic deadlock that defined the rest of the war.
The Schlieffen Plan failed for three connected reasons: Belgian resistance at Liège cost critical days; Russia mobilised faster than expected, forcing Germany to divert troops east; and Joffre’s counter-attack at the Marne (5-12 September 1914) drove the over-extended German right wing back to the Aisne.