6th September 1914: First Battle of the Marne begins with a French counter-offensive against the advancing German army

On the morning of 6 September, the French Sixth Army attacked the German First Army near the River Ourcq while the French Fifth Army and British Expeditionary Force advanced into the gap between the German First and Second Armies. On 9 September, German Chief of Staff Helmuth von Moltke ordered a withdrawal, marking the transition from mobile warfare to the long period of trench warfare that ...