Low-lying ground extends one mile (1.6 km) on each side, rising abruptly to a line of steep cliffs 300–400 feet (91–122 m) high, then gently levelling to a plateau.

The Germans settled on the higher northern side 2 miles (3.2 km) beyond the crest, behind a dense thicket that covered the front and slope.

[1] In dense fog on the night of 13 September, most of the British Expeditionary Force (BEF) crossed the Aisne on pontoons or partially demolished bridges, landing at Bourg-et-Comin on the right and at Venizel on the left.

The French Fifth Army crossed the Aisne at Berry-au-Bac and captured the eastern tip of Chemin des Dames, a steep ridge named after the royal coach road Louis XV had built for his daughters.

East of Chemin des Dames, the French Fourth, Fifth and Ninth armies made only negligible progress beyond the positions they had reached on 13 September.

Trench warfare was also new for the Germans, whose training and equipment were designed for a mobile war to be won in six weeks, but they quickly adapted their weapons to the new situation.

The German Army used only percussion shells, which, according to Canadian sources, "not one in several hundred ever hit its aerial target, and fell to earth frequently at some point in the British lines and there burst."

For a three-week period following the unexpected development of trench warfare, both sides gave up frontal assaults and began trying to envelop each other's northern flank.

One 6-inch gun poked out at each mile; none of these forts had high explosive projectiles or smokeless gunpowder and several thousand surrounding acres had been cleared to provide unobstructed fields of fire.

At daybreak on 29 September, General Hans von Beseler, called out of retirement at the age of sixty-five, arrayed six divisions in an arc facing the outer ring of forts.

Belgian guns belched dense, black smoke, revealing their exact location and the fields cleared by the defenders deprived the forts of any concealment.

A British Royal Marine Division joined the defending troops during the attack, but even this combined force was unable to stem the German drive.