The Great War mobilised France from August 1914 to November 1918. After the Marne, the front stabilised in trenches; Verdun and the Somme became symbols of attrition. In 1917 mutinies and exhaustion; in 1918 the Allied offensive with American support forced the Armistice of 11 November.
1914–1915
German invasion through Belgium, Battle of the Marne, “race to the sea”, trench warfare; costly offensives in Artois and Champagne.
1916–1917
Verdun (February–December 1916), Somme, Chemin des Dames; political and military crisis; arrival of US forces.
1918 and aftermath
German spring offensives, then Allied counter-attack; Armistice; Treaty of Versailles (1919). Human and material losses reshaped the Third Republic. See the 20th century.