Plan XVII

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 <a href="/facts/Grand_Quartier_G%C3%A9n%C3%A9ral_(1914%E2%80%931919)/4VjmasPI">Grand Quartier Général</a>) developed from 1912 to 1914, to be put into effect by the <a href="/facts/French_Army/NCnjovlu">French Army</a> in the event of war between France and <a href="/facts/German_Empire/lwQutJyN"> Germany</a>. The plan was for the mobilisation, concentration and deployment of the French armies to make possible an invasion either of Germany or of (neutral) <a href="/facts/Belgium/YKuMXP5j">Belgium</a> or of both, before Germany completed the mobilisation of its <a href="/facts/Military_reserve/sC6pR1qU">reserves</a> simultaneous with an expected <a href="/facts/Imperial_Russian_Army/eUBgLeFn"> Russian</a> offensive.
The French generals implemented the plan from 7 August 1914, with disastrous consequences for their armies, which suffered defeat in the <a href="/facts/Battle_of_the_Frontiers/FPBH5CWn">Battle of the Frontiers</a> (7 August – 13 September) at a cost of 329,000 casualties. The French armies (and the <a href="/facts/British_Expeditionary_Force_(World_War_I)/5rt91hcp">British Expeditionary Force</a>) in Belgium and northern France were forced into a retreat as far as the <a href="/facts/Marne_(river)/dY4ldBTv">Marne</a> river, where at the <a href="/facts/First_Battle_of_the_Marne/moIvptYr">First Battle of the Marne</a> (5–12 September), the German armies were defeated and forced to retreat to the <a href="/facts/Aisne_(river)/VzGUWIN2">Aisne</a> river, eventually leading to the <a href="/facts/Race_to_the_Sea/CcwSDys2">Race to the Sea</a>.

Plan XVII open-in-new

Plan XVII