The
Battle of Mons was the first major action of the
British Expeditionary Force (BEF) in the
First World War. It was a subsidiary action of the
Battle of the Frontiers, in which the
Allies clashed with
Germany on the French borders. At Mons, the
British Army attempted to hold the line of the Mons–Condé Canal against the advancing
German 1st Army. Although the British fought well and inflicted disproportionate casualties on the numerically superior Germans, they were eventually forced to retreat due both to the greater strength of the Germans and the sudden retreat of the
French Fifth Army, which exposed the British right flank. Though initially planned as a simple tactical withdrawal and executed in good order, the British
retreat from Mons lasted for two weeks and took the BEF to the outskirts of
Paris before it counter-attacked in concert with the French, at the
Battle of the Marne.