Trench warfare begins After their initial success on the Marne, Entente and German forces began a series of outflanking manoeuvres to try to force the other to retreat, in the so-called Race to the Sea. Britain and France soon found themselves facing entrenched German positions from Lorraine to Belgium's Flemish coast. The sides took set positions, the British and French seeking to take the offensive while Germany sought to defend the territories they had occupied. One consequence of this was that the German trenches were much better constructed than those of their enemy: the Anglo-French trenches were only intended to be 'temporary' before their forces broke through the German defences. Neither side proved able to deliver a decisive blow for the next four years, though protracted German action at Verdun (1916) and Allied failure the following spring brought the French army to the brink of collapse. Futile attempts at more frontal assaults, at terrible cost to the French poilu infantry, led to mutinies which threatened the integrity of the front line.
In the trenchesAround 800,000 soldiers from Britain and the Empire were on the Western Front at any one time, 1,000 battalions each occupying a sector of the line from Belgium to the Arne and operating a month-long four stage system, unless an offensive was underway. The front contained over 6,000 miles of trenches. Each battalion held its sector for around a week before moving back to support lines and then the reserve lines before a week out-of-line, often in the Poperinge or Amiens areas.