Upon the assassination of Archduke Franz Ferdinand, the European powers were quickly engulfed in an all-out war now known as World War I. Germany had prepared for this scenario years in advance, though the failure of the Schlieffen Plan led to a long drawn out conflict.
Nearly every country nowadays will plan for future conflicts. These plans are typically called “wargaming.” The modern version of wargaming was invented by Prussia in the 18th century, but not adopted widely by other nations until after the Franco-Prussian War of 1870-1871.
The dominant German victory in the war was largely credited with their wargaming plans and other nations adopted the practice so as not to be left behind.
In the lead up to World War I, Europe increasingly became caught up in a series of entangling alliances. Should one nation go to war, it could drag virtually the entire continent along with it. A classic description of Europe at the time was of a “powder keg” just waiting to explode.
The primary divisions were among the Triple Alliance (Germany, Austria-Hungary, and Italy) as well as the Triple Entente (Great Britain, France, and Russia). Russia also supported the Balkan region, including Serbia.
When Austria-Hungary opened the conflict with an attack on the Serbian capital of Belgrade, the first domino fell, and Europe went to war.
The German Schlieffen Plan had prepared the nation for this exact moment and now was the time to implement it.
What Was the Schlieffen Plan?
Two Front War
The Schlieffen Plan was the German grand strategy to fight, and win, a two front war against France and Russia. The plan was devised and wargamed in 1905 by then-Chief of the General Staff of the German Army, Alfred von Schlieffen.
Schlieffen had great respect for the powers of France and Russia and knew Germany stood little chance in an all-out simultaneous two front war against both. It is thus that he devised several different strategies in 1905 for various potential future conflicts.
Schlieffen favored the use of a strong defense, followed by a devastating counter-offensive to defeat Germany’s enemies. This plan would make use of the extensive German rail network to quickly move troops between fronts and defeat each nation one at a time. This plan was later known as Aufmarsch II West.
It called for 80% of German forces along the western border, and 20% on the eastern border. Both fronts would initially begin on the defense, though unleash fierce counter attacks on first on the French.
Then troops would be sent from the west to the east to launch a subsequent counterattack on the Russians. This was meant to be the main German strategy in a two front war with France and Russia.
One Front War
However, in order to maximize German flexibility and preparedness, Schlieffen also devised an offensive strategy for a one-front war solely with France. This plan, named Aufmarsch I West, is what is now known as the Schlieffen Plan of WWI.
The Schlieffen Plan called for Germany to take the offensive and attack France. Instead of doing this head-on against the heavily fortified French border, Germany would instead first invade neutral Belgium and the Netherlands and then attack France through their northern borders.
Once in French territory, the German attackers would then pivot south in a hinge-like movement, enveloping the French army. In the process, Paris could be encircled and captured. Schlieffen envisioned the attack would take no more than 6 weeks, as the capture of Paris and encirclement of the French army would lead France to seek peace.
Schlieffen anticipated fierce French resistance, and thus knew that this strategy would only succeed if the entire Germany army was deployed against France. In short, the offensive strategy now known as the Schlieffen Plan was only meant for a one front war, with Russia remaining neutral.
As Schlieffen retired from service in 1906, he was replaced by Helmuth von Moltke (the Younger). Moltke implemented some changes to the plan and was the leader in charge to execute the plan at the outset of WWI.
Importantly, despite the obviousness of a two-front war against both Russia and France, Molke decided to implement both Aufmarsch I West and Aufmarsch II West.
Germany would go on the offensive against France, but with only 80% of their forces as the other 20% were tied up on the eastern border against Russia. It was believed that Russia would be slow to mobilize for war, and if France was defeated in 6 weeks, Germany could then deal with the Russian juggernaut.
With these revisions and ultimately incorrect assumptions, the brilliant Schlieffen Plan was doomed for failure.
The Schlieffen Plan in WWI
Germany began its execution of the modified Schlieffen Plan on August 4, 1914 with the invasion of neutral Belgium. Belgian resistance was strong, and it took the German army longer than anticipated to make their way through the country.
Great Britain subsequently declared war on Germany for violating Belgium’s neutrality. Despite this, Germany had advanced into French territory by the end of August and the French forces were in full retreat.
The French grand strategy, titled Plan XVII, was to attack Germany across the border at their former provinces of Alsace and Lorraine, south of Belgium and Luxembourg. Ironically, this is exactly what Germany was anticipating.
The French advancement east would make it easier for the Schlieffen Plan to envelop the French army when it hinged south after making its way through Belgium.
Despite a vicious attack, the French were repulsed and forced to retreat lest they be encircled by the Germans advancing through Belgium.
As the German army moved through France and turned south they made it to within 20 miles of Paris, near the Marne River. Despite the difficulties the Schlieffen Plan actually looked as if it might succeed.
The Attack Falters
However, a key vulnerability formed in the German’s attack. During the march south through France a hole formed between the main German forces. They were forced to close the gap, though this meant that the western most army did not go far enough west.
That army was meant to land on the western side of Paris so as to encircle the city. Instead, they ended up east of the city, exposing their right flank to the Parisian defenders themselves.
In addition, as the Germans marched through France, their advance slowed. The German Army was moving too fast for their supply lines to keep up, and the soldiers were weary and underfed.
The slowing advance allowed France time to regroup and organize a defensive stand. France did just that at the Marne River, east of Paris.
At the subsequent Battle of the Marne a heroic effort by the French defenders repulsed the Germans and sent them retreating back. The German offensive and modified Schlieffen Plan had failed.
It is not confirmed, though allegedly after the failure at Marne the defeated General Moltke reported to Kaiser Wilhelm II, “Your majesty, we have lost the war.”
Regardless of whether those words were spoken, the hopes for a quick victory on the Western Front were dashed. The Germans retreated back, settled in, and dug deep trenches in preparation for a long war of attrition.
Why Did the Schlieffen Plan Fail?
The Schlieffen Plan failed for several reasons. Firstly, the Schlieffen Plan implemented was not the one that was supposed to occur. In a two front war the Schlieffen Plan called for a defensive first strategy, followed by strategic counterattacks.
Instead, Germany went on the offensive on the Western Front, despite not having the manpower. Schlieffen himself estimated that Germany would need 48.5 corps to succeed in an offensive attack, yet Molke only deployed 34 corps, 6 of which were held back to defend Alsace and Lorraine.
The lack of manpower led to a weakened attack that stalled and caused the formation of a gap in the German lines that French forces exploited.
The failure of the Schlieffen Plan also resulted from several incorrect assumptions that hampered the attack. First, they underestimated how quickly the Russians could deploy their troops.
Six weeks were estimated, leading Moltke to believe France could be defeated before the Russians fully mobilized. In reality, the Russians first attacked in less than half that time, forcing Moltke to further weaken the German offensive on the Western Front by sending additional troops east.
The Germans also downplayed the political ramifications of invading neutral Belgium. The Germans did not believe the British would stand firm on their commitment defending the Belgians and they would not become bogged down in a continental European war.
This assumption proved to be false, as Britain joined the war just days after the German invasion of Belgium. Fighting the British and French together on the Western Front was never part of the German strategy.
The combination of the execution of the wrong strategy and a series of key incorrect assumptions led to the failure of the Schlieffen Plan. With it Germany was forced to settle into a brutal war of attrition that dramatically lowered their probability of victory in World War I.