Second Battle of the Marne - Wikipedia

On August 6, 1918, the World War I Second Battle of the Marne ended.
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The battle began on 15 July 1918 when 23 German divisions of the First and Third armies—led by Bruno von Mudra and Karl von Einem—assaulted the French Fourth Army under Henri Gouraud east of Reims (the Fourth Battle of Champagne (French: 4e Bataille de Champagne)). The U.S. 42nd Division was attached to the French Fourth Army. Meanwhile, 17 divisions of the German Seventh Army, under Max von Boehn, aided by the Ninth Army under Johannes von Eben, attacked the French Sixth Army led by Jean Degoutte to the west of Reims (the Battle of the Mountain of Reims (French: Bataille de la Montagne de Reims)). Ludendorff hoped to split the French in two.

East of Reims the French Fourth Army had prepared a defense in depth to counter an intense bombardment and infiltrating infantry. [1] [2] Their main line of resistance was four to five km behind the front, beyond the range of the enemy field guns, it was a continuous trench line — to prevent infiltration— dug on a reverse slope so it could not be overlooked by enemy artillery observers on the ground. Between the front and the main line of resistance were two lines of strong points, again mostly on reverse slopes. The French gun line behind the front was lightly manned, but the remaining guns fired frequently, so the Germans did not detect its weakness from rate of firing, although aerial observers did spot a concentration of field guns behind the main line of resistance. German offensive tactics stressed surprise, but French intelligence based on aerial observation gave clear warning and from twenty-seven prisoners taken in a trench raid they learned the hour for the attack.[3]

The German bombardment was scheduled for 12:10. The French opened fire on the German assault trenches at 11:30, naturally shaking the confidence of attackers. When the Germans opened fire they pounded the almost empty French front line and their counter-battery fire struck many vacated gun pits. The attackers moved easily through the French front and then were led onward by a rolling barrage, which soon was well ahead of the infantry because they were held-up by the points of resistance. When they encountered the French mainline they were ordered to rest, regroup and wait until their field guns were moved into range. They attacked the main line at 08:30 the following morning, an hour after their schedule. They were stopped by accurate fire by the bulk of the French artillery. They tried again at noon, but failed. A French counter-attack gained little ground, but convinced the German commanders that they could not prevail. The Fourth Army was now able to send reinforcements to their neighbors to the west who had not fared as well.

In the west on the opening day of the offensive the defenders of the south bank of the Marne had to hold the river bank by enduring an intense three hour bombardment, including many gas shells. Under this cover stormtroopers swarmed across the river in every sort of transport—including 30-man canvas boats and rafts. They began to erect skeleton bridges at 12 points under fire from the Allied survivors. Some Allied units, particularly Colonel Ulysses G. McAlexander's 38th Infantry Regiment of the 3rd U.S. Infantry Division, the "Rock of the Marne", held fast or even counterattacked, but by evening, the Germans had captured a bridgehead on either side of Dormans 4 mi (6.4 km) deep and 9 mi (14 km) wide, despite the aerial intervention of 225 French bombers, dropping 44 short tons (40 t) of bombs on the makeshift bridges. Ludendorff regarded their advance as "the very pinnacle of military victory".[4]

The French were reinforced by the British XXII Corps and 85,000 American troops, the German advance on stalled 17 July 1918.