The British Expeditionary Force arrived in France by boat, arriving shortly after Britain's declaration of war on Germany. Britain declared war on Germany on 4 August 1914, General Sir John French crossed to France on 14 August with detachments of the BEF, disembarking at the Channel port of Boulogne. French then and indicated that the BEF would be ready to begin operations against German forces by 24 August.

The British, nor any other belligerent on the Western Front, were given time to dig in and construct their trench networks. Trenches were dug hurriedly and in an ad-hoc manner (at least initially) and occurred organically as a direct result of the weapons technology of the time. The destructive capabilities of artillery and the threat posed by machine guns meant that the safest place to be was below ground level. The first trenches started as individual foxholes, dug to protect an individual soldier. In order to move around safely, those holes were expanded, deepened and connected, eventually creating connected networks of sub-ground level earthworks. One side might do this first and, unable to reach these new positions, the other side would do the same rather then withdraw and yield ground to the enemy. Overtime, trench systems were improved upon, expanded and made more elaborate.