12–15 September

When the Germans turned to face the pursuing Allies on 13 September, they held one of the most formidable positions on the Western Front. Between Compiègne and Berry-au-Bac, the Aisne River winds westward and is about 100 feet (30 m) wide, ranging from 12–15 feet (3.7–4.6 m) deep. 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. Low crops in the unfenced countryside offered no natural concealment to the Allies. Deep, narrow paths cut into the escarpment at right angles, exposing any infiltrators to extreme hazard. The forces on the northern plateau commanded a wide field of fire.^[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. At Chivres-Val east of Venizel, there was an escarpment the Germans had selected as their strongest position. 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. Contact was established along the entire front. 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. Under the thick cover of the foggy night, the BEF advanced up the narrow paths to the plateau. When the mist evaporated under a bright morning sun, they were mercilessly raked by fire from the flank. Those caught in the valley without the fog's protective shroud fared no better.

It soon became clear that neither side could budge the other and since neither chose to retreat, the impasse hardened into stalemate, that would lock the antagonists into a relatively narrow strip for the next four years. On 14 September, Sir John French ordered the entire BEF to entrench, but few entrenching tools were available. Soldiers scouted nearby farms and villages for pickaxes, spades and other implements. Without training for stationary warfare, the troops merely dug shallow pits in the soil. These were at first intended only to afford cover against enemy observation and artillery fire. Soon the trenches were deepened to about seven feet. Other protective measures included camouflage and holes cut into trench walls then braced with timber.

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. Siege howitzers now lobbed massive shells into the Allied trenches. Skillful use of trench mortars and hand and rifle grenades (first used against British troops on 27 September), enabled the Germans to inflict great losses upon Allied troops, who had neither been trained nor equipped with these weapons. Searchlights, flares and periscopes were also part of the German equipment intended for other purposes, but put to use in the trenches.

A shortage of heavy weapons handicapped the British. Only their 60-pounders (four guns to a division) were powerful enough to shell enemy gun emplacements from the Aisne's south shore, and these guns were inferior to German artillery in calibre, range and numbers. Four artillery battery of 6-inch (150 mm) guns (a total of sixteen), were rushed from England. Although a poor match against the German 8-inch (200 mm) howitzers, they helped somewhat. Defensive firepower was limited to rifles and two machine guns allotted to each battalion. The British regulars were excellent marksmen but even their combined accuracy was no match for the German machine guns and grenades.

British aircraft were used to report troop movements, although few were equipped with wireless. Aviators were able to recognise the advantage of observing artillery fire. On 24 September, Lieutenants B.T. James and D.S. Lewis detected three well-concealed enemy gun batteries that were inflicting considerable damage on British positions. They radioed back the location of the batteries, then droned in a wide circle, waiting to spot their own gunners' exploding shells. Anti-aircraft fire was desultory and inaccurate. 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."