World War I: Schlieffen and His Plan

How Mobilization Became the Trigger for War

[For other articles in this World War I historical series, see World War I: The Question of Blame and From Waterloo to the Marne.]

Build no more defensive forts, build railways instead.

– Alfred Graf von Schlieffen, chief of the German General Staff, 1905

Schlieffen and His Plan

The French-Russian alliance had raised the prospect that Germany might face a war on two fronts. In response, Kaiser Wilhelm II ordered Alfred Graf von Schlieffen, chief of the German General Staff, to develop a plan to successfully fight both France and Russia. The strategy Schlieffen developed would have a profound effect on both the scope and the conduct of the war.

What came to be called the Schlieffen Plan was not the first attempt to craft a German strategy to fight a two-front war. Such a strategy had already existed prior to Schlieffen. Simply put, that strategy had been "hold in the west and attack in the east." The traditional invasion route into eastern France was through the Belfort Gap or "Burgundian Gate," a relatively flat, high plateau between the northern rim of the Jura Mountains and the southernmost part of the Vosges Mountains. This was the historic invasion route from central Europe into France. It was the invasion route that German armies had taken during the Franco-Prussian war of 1870. Subsequently, the French had heavily fortified the area. An extensive network of new forts was built centered on the four "front-line" cities of Belfort, Epinal, Toul and Verdun.

The German General Staff reasoned that a breakthrough through the heavily defended Belfort Gap would be difficult -- a point driven home by the subsequent slaughter at the Battle of Verdun in 1916. Its strategy was to pin down or "hold" French forces on the western front while it first dealt with Russian forces in the east. Russian mobilization was expected to be slow. Germany's forces were better trained and more mobile. The combined Austrian and German armies would deliver a knockout blow to Russian forces and force Russia out of the war. Bereft of its Russian ally, France could not hope to take on the combined might of Germany and Austria, and would have little choice but to sue for peace.

In December 1905, Schlieffen began circulating his proposed plan to the General Staff. The first version of the Schlieffen Plan -- there would be many modifications -- reversed the prevailing strategy. It envisioned a rapid thrust westward with the bulk of the German army to envelop the French army and annihilate it in less than 45 days. With France knocked out of the war, Germany would then use its modern railroad network to quickly transfer troops to the east and deal with its Russian opponents.

Russia, Schlieffen believed, would need at least six weeks to mobilize. That would give the Germany army a window in which to defeat France. Even if the Russians advanced into eastern Germany, he reasoned, these gains would be short-lived and would easily be reversed.

By using its more rapid mobilization to its advantage, Schlieffen reasoned that he could bring the whole weight of the German army on each of its opponents in turn. The key to Schlieffen's plan was to engage and destroy the French army and quickly knock France out of the war. To do this, he envisaged a broad, enveloping movement into northern France that would bypass Paris, trap the French army between the German right wing and its central and left wing, and then surround it and annihilate it.

A rapid thrust through the Belfort Gap, however, was unlikely, given its extensive fortifications. There was one other alternative route, a thrust through the Meuse valley across Belgium to the English Channel and then a pivot into northern France. The Meuse Valley, or Meuse Gap, was straddled by the Belgian city of Liege, which was in turn protected by a chain of 12 forts.

The original Schlieffen Plan had called for an invasion of Belgium, and also of a tiny sliver of the Netherlands, in order to better outflank the Belgian forts defending Liege. Subsequent revisions dropped the incursion into the Netherlands. The Dutch were thus able to retain their neutrality during the war. The proposed invasion of Belgium added a political element to the Schlieffen Plan whose consequences were not fully appreciated at the time.

By invading Belgium, Germany made it a virtual certainty that Great Britain would intervene on behalf of France in the defense of Belgium. The Anglo-French accords of 1905 did not specifically obligate Great Britain to come to the defense of France in the event she had been invaded. Both the British General Staff and the British government had given private assurances to the French government, and its military, of their willingness to come to their aid, but it is unlikely that a formal treaty of alliance would have had sufficient parliamentary support or public approval to be ratified.

There are too many possible "what ifs" to speculate how both the war and its outcome might have been altered had the Schlieffen Plan never been adopted by the German General Staff. Had Germany pursued a policy of "holding" in the west, what would France and England have done? Would France have invaded Germany? At the very least, given its preoccupation with the restoration of the "lost provinces" of Alsace and Lorraine, it is likely that France would have seen German preoccupation with a war in Russia as an opportunity to take back its historic territory.

In this case, the "Western Front" might well have been limited to a relatively narrow engagement in the 25-mile Belfort Gap and not the 200 miles of trench warfare that would ultimately result. In such a narrow theater, the participation of the British army would have been superfluous. Unburdened by its 1839 treaty commitment to uphold Belgian neutrality, British involvement might have been limited to bottling up the German High Seas fleet in the Baltic and to defending the French coasts from naval attack by the German fleet. British involvement might have stopped well short of committing ground troops, much less mobilizing the manpower of the Empire.

The Trigger of Mobilization

Schlieffen's plan to knock France out of the war quickly meant that the rapid mobilization of troops was not just an important tactical advantage but a critical element for achieving victory. On Aug. 1, in response to the German declaration of war against Russia, the French government ordered a full mobilization. The Germans followed suit. On Aug. 3, after Paris had refused to answer Berlin's demand to remain neutral, Germany declared war on France.

Simultaneously, Germany informed King Albert's neutral Belgian government that "it would treat it as an enemy" if it did not permit the free transit of German troops across its land. Belgium immediately ordered a full mobilization. Less than 24 hours later, in accordance with the strategy laid out in the latest version of the Schlieffen Plan, Germany invaded Belgium. In London on the stroke of midnight, Aug. 4, Prime Minister Herbert Asquith's government, having received no German guarantees to respect Belgium's neutrality, began a full mobilization of the army and fleet, and declared war on Germany.

By the first week of August, even as Europe was still in the midst of an all-out mobilization, hostilities had already commenced. The term mobilization is used freely to describe the process of calling up reservists in each of the belligerent countries. The process, however, was fundamentally different in each country.

German military units were geographically based. Their muster stations and arms depots were local. Once a mobilization order was issued, a unit could be assembled, armed and dispatched within 24 hours. Given Germany's extensive and efficient rail network, a military unit could be on the front within 48 hours of being called up.

French mobilization was slower because the composition of French military units was geographically diverse. Muster stations for French recruits were typically farther away, requiring a train journey to the muster station and, then, once assembled and armed, a second journey to their designated deployment. That difference meant that French mobilization was, at best, 2-3 days slower than that of Germany. Most of the time, France lagged about a week behind Germany in mobilizing and deploying its troops. In both the French and German cases, reservists would have undergone some prior military training.

Russian mobilization was an altogether different process. Russia's western front was organized into six military districts. Each district had multiple muster stations. Typically, these were located well back from the front lines -- in some cases, as much as 200 miles back. Three of these military districts fronted on German territory, and three fronted on Austrian territory. In August 1914, there were approximately 5,000 miles of paved roads in Russia, less than 1% of all roads. Russian track mileage was slightly greater than that of Germany, but it had to service an area many times larger.

Reservists had to travel long distances to their muster stations, often by foot. It was only after they had arrived at the military depots that they were assigned to their military units. Only then would Russian recruits meet their fellow soldiers and, more importantly, their officers. Few of those recruits had received prior military training. More than 60% of them were illiterate.

After their activation, military units would then proceed to their front lines, again, typically on foot. The result was that Russian mobilization was inherently far slower than either the French or German process. It took Russia between four and eight weeks to mobilize its military fully. Until its soldiers were ready, Russia relied on standing cavalry units to provide a screen for its forces and to defend its frontiers.

Austrian mobilization was also regionally based. Unlike Germany, however, their regions were broader, often corresponding to provinces. Additionally, as one might expect in a polyglot empire, military units were further broken down by native language. Troops drawn from the Friuli region, for example, were organized into Italian-speaking and German-speaking regiments.

This organizational scheme also meant that Serb units from Hungary, for example, were organized into separate formations from Serb units from Bosnia. The "ethnic, geographic and language" classification of military units ensured that they were not deployed in areas that might create personal conflicts, or divided loyalties, and raise questions about their reliability. Italian-speaking troops, for example, were usually deployed on the eastern front, far away from their brethren on the Italian front.

Great Britain did not have a large standing army, nor did it rely, at least not initially, on a large cadre of reservists that needed to be called up. British mobilization consisted primarily of activating the Royal Navy to its war stations and deploying its standing troops to the front lines.

The process of mobilization was extremely disruptive to civilian life. German mobilization required between 5,000 and 10,000 trains. Each train was scheduled at a precise 20-minute interval, each carrying the maximum number of cars that would fit on the station platform to allow all troops to disembark at the same time.

French mobilization required between 5,000 and 8,000 trains, comparably organized and scheduled. When a mobilization order was given, the entire civilian railroad schedule was suspended, and the rail network was turned over to military use.

Some historians have argued that it was the generals and their rush to mobilize that precipitated the war. Had mobilization been delayed, had diplomacy been given a little more time to find a peaceful solution, a general war might well have been averted. This statement is not entirely correct, although there is some element of truth in it.

The decision to mobilize was not made by the generals but by the civilian authorities. Whether it was a hereditary monarch or a democratically elected prime minister, it was ultimately a decision made by each nation's government, not its military leaders. It was a political as much as a military decision. In every country, the announcement of a general mobilization was met with spontaneous public celebrations and manifestations of patriotic support for the government.

No doubt there were generals who argued that prudence and an abundance of caution dictated that the decision to mobilize was better made sooner than later. In that sense, they were right. The very process of mobilization, and most importantly, the varying speed at which each nation could mobilize, created a significant element of instability.

First, the decisions to mobilize were by necessity interlocking. If one party mobilized, all its potential opponents would be hard pressed not to follow suit. The first mobilization made it virtually inevitable that it would trigger a cascading effect. Secondly, the varying speed at which each country mobilized also magnified the instability of the system. A faster mobilization meant a faster deployment and represented a significant tactical opportunity. For Germany, delaying its mobilization meant it was squandering a major battlefield advantage and undermining its war plan.

For France, whose mobilization was 3-7 days behind Germany's, delay meant it fell even further behind, and its peril was magnified proportionally. Finally, the process of mobilization, once started, was impossible to stop until it had run its course. To stop a mobilization in midstride would have produced chaos, with reservists and their units stranded, and would have left that country's forces in disarray. In fact, no military staff had a way of stopping a mobilization in midstride. They couldn't have done it even if they had wanted to.

By the first week of August, millions of men were arriving on the front lines. War had been declared. The fuse ignited at Sarajevo, just 33 days ago, had reached its powder keg.

Joseph V. Micallef is a military historian, bestselling author, keynote speaker, syndicated columnist and commentator on international politics and the future.

Want to Know More About the Military?

Be sure to get the latest news about the U.S. military, as well as critical info about how to join and all the benefits of service. Subscribe to Military.com and receive customized updates delivered straight to your inbox.