Heinrich von Kluck, the First Army Commander of the right wing of a German advance, decided to move his troops north instead of west of Paris to meet Michel-Joseph Maunoury’s French Sixth Army. Because the Allies were able to intercept German radios, French commander-in-chief Joseph Joffre was able to keep France from Germany's occupation. Historian Christopher Klein supports our argument:
First Battle of Marne
French Troops at the First Battle of Marne, 1914, History.com
When the war broke out, Germany planned to quickly invade France with the aggressive Schlieffen Plan. At the First Battle of Marne, Anglo-French forces were ready to stop German forces moving through Belgium and France.
Map of the First Battle of Marne, Geocities.
“Dubbed the ‘Miracle of the Marne,’ the strategic victory for the Allies proved to be a critical turning point in World War I. Paris had been saved from capture. Notions of a short war had been dashed. The Schlieffen Plan had been torn to tatters.” ~(Klein 2018, 1)