The British Expeditionary Force fought its first major engagement of the First World War at Mons, Belgium, on 23 August 1914, less than three weeks after Britain declared war on Germany.

The BEF had crossed to France under Field Marshal Sir John French to support the French armies. It was small compared with the forces deployed by Germany and France, consisting initially of four infantry divisions and a cavalry division. Many of its soldiers were experienced regulars trained in rapid rifle fire.

The British took positions along the Mons-Condé Canal on 22 August after cavalry patrols reported the German advance. They were on the left of the French Fifth Army and directly in the path of the German First Army.

German troops attacked the following day. British rifle fire inflicted heavy casualties and slowed the advance, but pressure grew around the canal crossings. At Nimy, men of the 4th Royal Fusiliers defended two bridges under heavy fire.

Lieutenant Maurice Dease continued operating machine guns despite being wounded several times. After Dease was fatally wounded, Private Sidney Godley continued firing while other troops withdrew. Godley was wounded and later captured. Both men received the Victoria Cross.

The BEF could not remain at Mons. The withdrawal of French forces on its right left the British position exposed, and orders were given to fall back. The fighting on 23 August therefore became the beginning of a long retreat southwards.

The Retreat from Mons continued towards the River Marne, with further fighting at places including Le Cateau. The Germans halted their advance at the First Battle of the Marne in September.