After an initial period of relatively rapid maneuver during which the German forces pushing through Belgium and the French and British forces attempting to stymie them made an endless series of abortive flanking movements that extended the lines to the sea, a stalemate naturally tended to develop. The infamous trench lines soon snaked across the French and Belgian countryside, creating an essentially futile static slaughterhouse whose sinister memory remains to this day.

Until the war of maneuver returned in 1918 and led to a decisive outcome for the war, the nexus of this horror lay in the rainy, sodden levels and low ridges of Flanders, near the medieval town of Ypres. In this tiny fragment of Europe, half a million men died over the course of three major battles and the times of attrition between, perishing in a squelching pit of mud, blood-tinged water, and rotting human flesh. In fact, with the exception of a few hours on Christmas Day 1914, the shelling, sniping, raids, and bloodshed in Flanders never ceased from the moment of first between the British Expeditionary Force (BEF) and the Imperial German army.

The Ypres salient bulged a few miles forward into Belgium, representing the only part of that nation the Germans had not occupied. Held by a mix of British, French, Canadian, Belgian, and colonial troops, this thorn in the Germans' side had held off massive but clumsily handled attacks by barely-trained German volunteers and conscripts in late 1914 at the First Battle of Ypres. Each side had attempted to launch a major offensive through Ypres at the same time, leading to a blood-soaked encounter battle that, after weeks of futile butchery amid the small farms, hedgerows, canals, and tracts of woodland, devolved into a grim stalemate. Lines of trenches faced each other and sniping, artillery bombardment, and small actions led to an ongoing stream of casualties.