Question: where did the second battle of marne take place

title: Second Battle of the Marne
text: The Allied preparation was very important in countering the German offensive . It was believed that the Allies had the complete picture of the German offensive in terms of intentions and capabilities . The Allies knew the key points of the German plan down to the minute . There is a legend , possibly true , that engineer Cpt . Hunter Grant , along with the help of engagement coordinator and engineer Cpt . Page , devised a deceptive ruse . A briefcase with false plans for an American countererattack was handcuffed to a man who had died of pneumonia and placed in a vehicle which appeared to have run off the road at a German - controlled bridge . The Germans , on finding and being taken in by these plans , then adjusted their attack to thwart the false Allied plan . Consequently , the French and American forces led by Foch were able to unleash a different attack on exposed parts of the enemy lines , leaving the Germans with no choice but to retreat . This engagement marked the beginning of a German withdrawal that was never effectively reversed . In September 1918 nine American divisions ( about 243,000 men ) joined four French divisions to push the Germans from the St. Mihiel salient .