During the Battle of the Aisne (12 -15 September 1914) the character of the First World War changed entirely when both sides began to dig trenches.
Halting the retreat
After the Allied success at the Battle of the Marne, which put an end to the German advance through France, the German Army had been steadily retreating. By the middle of September the Allies were approaching the River Aisne. Field Marshall Sir John French took the decision to send his troops across the river, however he had no way of knowing whether the Germans were still retreating.
In fact the German Army had dug-in in shallow trenches along the Chemin des Dames ridge. When French sent his men against the German positions, time and again they were cut down by machine-guns and artillery fire.
The order is given
It soon became clear that this was not simply a rear-guard action and that the German retreat was at an end. French then issued an order to the British Expeditionary Force to begin digging trenches.
The British soldiers used whatever tools they could find, taking shovels from nearby farms, and even in some cases digging the earth with their hands. They could not have known that these shallow holes would soon stretch the length of the Western Front, or that both sides would occupy them for the next three years.