It was one of five armies created and placed on a war footing by the Grand Quartier Général when Plan XVII was launched in response to the German attack of August 1914.

The 9th Cavalry Division (France) [fr] (from Tours) was formed from the 9th, 10th and 11th regions, and was commanded by general Jean de l'Espée.

[3] 15–18 July: Battle of Champagne, German offensive towards the Hand of Massiges [fr] at Prunay, halted in front of the French resistance position, after voluntary abandonment of the front lines (battle of Prosnes-Massiges).

On the 8th and 9th of October, working in coordination with I Corps, the French Fourth Army conducted a pincer attack that resulted in the Germans withdrawing.

[10] From 16-20 October, there was a French offensive with heavy fighting in the Olizy, Vouziers region.