science

Plan XVII

Plan XVII is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Plan XVII rather than just read about it. In short: Plan XVII (pronounced [plɑ̃ dis.sɛt]) was the name of a "scheme of mobilisation and concentration" which the French Conseil Supérieur de la Guerre (the peacetime title of the French Grand Quartier Général) developed from 1912 to 1914, to be put into effect by the French Army in the event of war between France and Germany. The plan was for the mobilisation, concentration and deployment of the French armies to make po…

Key takeaways

Plan XVII belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Plan XVII to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Plan XVII from memory before moving on to harder problems.

Reference excerpt

Plan XVII (pronounced [plɑ̃ dis.sɛt]) was the name of a "scheme of mobilisation and concentration" which the French Conseil Supérieur de la Guerre (the peacetime title of the French Grand Quartier Général) developed from 1912 to 1914, to be put into effect by the French Army in the event of war between France and Germany. The plan was for the mobilisation, concentration and deployment of the French armies to make possible an invasion either of Germany or of (neutral) Belgium or of both, before Germany completed the mobilisation of its reserves simultaneous with an expected Russian offensive. The French generals implemented the plan from 7 August 1914, with disastrous consequences for their armies, which suffered defeat in the Battle of the Frontiers (7 August – 13 September) at a cost of 329,000 casualties. The French armies (and the British Expeditionary Force) in Belgium and northern France were forced into a retreat as far as the Marne river, where at the First Battle of the Marne (5–12 September), the German armies were defeated and forced to retreat to the Aisne river, eventually leading to the Race to the Sea.

Background

Concentration plans 1871–1911 After the French defeat in the Franco-Prussian War 1870–1871, from 1874–1880, General Raymond Adolphe Séré de Rivières (20 May 1815 – 16 February 1895) oversaw the construction of the Séré de Rivières system, a line of fortresses 65 km (40 mi) long from Belfort to Épinal and another line of similar length from Toul to Verdun, about 40 km (25 mi) back from the frontier. The River Meuse flows northwards from Toul to Verdun, Mézières and Givet on the Belgian border and a tributary of the Moselle between Belfort and Épinal, near parallel to the 1871–1919 French-German border. The Trouée de Charmes (Charmes Gap), 70 km (43 mi) wide, between Épinal and Toul was left unfortified and the fortress city of Nancy was to the east, 12 km (7.5 mi) from the German frontier. A second series of fortifications, to prevent the main line being outflanked, was built in the south, from Langres to Dijon and in the north from La Fère to Rheims and from Valenciennes to Maubeuge, although for financial reasons these defences were incomplete in 1914. During the 1870s, the French army drew up concentration plans according to a defensive strategy, which exploited the Meuse and branches of the Moselle parallel to the 1871 border. The completion of the fortress lines between Belfort and Verdun in the late 1880s and railway building from the interior to the border, then gave the French army the means to contemplate a defensive-offensive strategy, in which a German attack would be repulsed and then followed up by a counter-attack. In August 1891, Plan XI was completed, with an option for an offensive as well as a defensive strategy from the start, to exploit the opportunity created by the improvement in relations between the Third Republic and the Russian Empire. The Franco-Russian Alliance (1892–1917) led to Plan XII in February 1892, in which an immediate invasion of Germany was considered possible. But from Plan XI to Plan XVI, the strategy remained defensive-offensive, French attacks being expected after the repulse of a German invasion.

In 1888, the French began to study a possible German offensive north of Verdun or through Belgium and Plan XII was written with a contingency for a German breach of Belgian neutrality. In 1904, this was given more attention after a German (Le vengeur [The Avenger]) sold a copy of the German concentration plan to French intelligence and described mobilisation methods and war plans. Using this windfall and other sources of information, the French adapted Plan XV of 1906, to be ready for a German invasion of Belgium and later plans contained increases in the forces to be assembled to the north and north-east of Verdun. Plan XVI of March 1909, anticipated a German enveloping manoeuvre through Luxembourg and Belgium, after the findings of a 1908 analysis by General Henri de Lacroix, in which he dwelt on the German preference for enveloping manoeuvres and predicted that two German armies would march through eastern Belgium, around the northern flank of the French fortress zone, one to emerge from the Ardennes at Verdun and the other at Sedan. Lacroix wanted to improve the prospects of the usual defensive-offensive strategy by assembling a new Sixth Army near Châlons-sur-Marne, (now Châlons-en-Champagne), 80 km (50 mi) west of Verdun, easily to move towards Toul in the centre, Verdun on the left or to the vicinity of Sedan and Mézières behind the northern flank.

Prelude

Concentration plans, 1911–1914

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Plan XVII

Start with the simplest possible case. Write down what Plan XVII claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Plan XVII before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Plan XVII ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Plan XVII

In research: Plan XVII appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Plan XVII in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Plan XVII is common in secondary-school and first-year university syllabi. It links to neighbouring topics 20th-century military history of France, German Empire in World War I, Military history of France during World War I, so understanding it makes those chapters shorter.
In everyday life: Look for Plan XVII outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Plan XVII in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Plan XVII means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Plan XVII out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Plan XVII in simple terms?

Why does Plan XVII matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Plan XVII?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Plan XVII.