Background
On the morning of 27 May 1918, the Germans began a bombardment (feuerwalze) of the Allied front lines with over 4,000 artillery pieces. The British suffered heavy losses, due to the fact that Duchene had ordered them to mass together in the front trenches, in defiance of instructions from the French Commander-in-Chief Henri-Philippe Petain. Huddled together, they made easy artillery targets.
The bombardment was followed by a poison gas drop. Once the gas had lifted the main infantry assault by 17 German Sturmtruppen divisions commenced, led by Crown Prince Wilhelm, the eldest son of Kaiser Wilhelm II.
Taken completely by surprise and with their defences spread thin, the Allies were unable to stop the attack and the German army advanced through a 40 km gap in the Allied lines. Reaching the Aisne in under six hours, the Germans smashed through eight Allied divisions on a line between Reims and Soissons, pushing the Allies back to the river Vesle and gaining an extra 15 km of territory by nightfall.
Victory seemed near for the Germans, who had captured just over 50,000 Allied soldiers and well over 800 guns by 30 May 1918. But after having advanced within 56 km of Paris on 3 June, the German armies were beset by numerous problems, including supply shortages, fatigue, lack of reserves and many casualties along with counter-attacks by and stiff resistance from newly arrived American divisions, who engaged them in the Battles of Chateau-Thierry and Belleau Wood.
On 6 June 1918, following many successful Allied counter-attacks, the German advance halted on the Marne, much as the "Michael" and "Georgette" offensives had in March and April of that year.'

Aftermath

Chemins des Dames Ridge