The Battle of the Marne was fought from 5th – 10th September, 1914. This battle would prove to be a major turning point of the Great War as it denied the Germans an early victory.
From the 13th September, 1914 the First Battle of the Aisne took place, with both sides starting to dig trenches. Then for a three-week period following the development of trench warfare each side gave up frontal assaults and began trying to encircle each other's flank. This period became known as the Race to the Sea: the Germans aimed to turn the Allied left flank, and the Allies sought to turn the German right flank.
While war in the trenches is described in horrific, the mud, water, the stench of rotting bodies, the enormous rats—the reality was that the trench system protected the soldiers to a large extent from the worst effects of modern firepower and Artillery.
In total the trenches built during the Great War, laid end-to-end, would stretch some 25,000 miles—12,000 of those miles occupied by the Allies, and the rest by the Central Powers.