On July 15, 1918, the German First and Third Armies attacked the French Fourth Army just east of Reimes, beginning what came to be known as the Second Battle of the Marne. By this point the German forces had been ravaged by influenza, and despite having successfully advanced in Northern France from March until June of that year, the Kaiser’s troops were overworked, undernourished, and dispirited. The German commander, General Erich Ludendorff, had led the spring offensive hoping to penetrate the Allied lines on the Western Front, thus rallying his troops while simultaneously providing Germany with one last opportunity for an end-run to Paris.
https://en.wikipedia.org/wiki/Second_Battle_of_the_Marne