The Battle of Charleroi, another of the frontier battles, was an action taking place 12–23 August 1914. The battle was joined by the French Fifth Army, advancing north towards the River Sambre, and the German Second and Third armies, moving southwest through Belgium. The Fifth army was meant to join the Third and Fourth armies in their attack through the Ardennes. However, this plan was put into effect assuming the Germans were not considering an assault further north, through Belgium—which was the German plan all along. Charles Lanrezac, commander of the Fifth Army, was strongly against the idea, fearing an attack from the north. However Joseph Joffre, chief-of-staff, rejected any such idea; after much persuasion, Lanrezac finally convinced him to move the Fifth Army northwards.