 Complete the following phrase:  The Great Retreat , also known as the retreat from Mons, was the long withdrawal to the River Marne in August and September 1914 by the British Expeditionary Force BEF and the French Fifth Army. The Franco-British forces on the Western Front in the First World War had been defeated by the armies of the German Empire at the Battle of Charleroi 21 August and the Battle of Mons 23 August. A counter-offensive by the Fifth Army, with some assistance from the BEF, at the First Battle of Guise Battle of St. Quentin failed to end the German advance and the retreat continued over the Marne. From 5 to 12 September, the First Battle of the Marne ended the Allied retreat and forced the German armies to retire towards the Aisne River and to fight the 