Opposing forces

The American forces initially consisted of 15 divisions of the U.S. First Army commanded by General John J. Pershing until October 16 and then by Lieutenant General Hunter Liggett.^[9] The logistics were planned and directed by then Colonel George C. Marshall. The French forces next to them consisted of 31 divisions, including the Fourth Army (under Henri Gouraud) and the Fifth Army (under Henri Mathias Berthelot).^[10] The U.S. divisions of the AEF were oversized (12 battalions per division versus the French-British-German nine battalions per division), being up to twice the size of other Allies' battle-depleted divisions upon arrival, but the French and other Allied divisions had been partly replenished prior to the Grand Offensive, so both the U.S. and French contributions in troops were considerable. All of the heavy equipment (tanks, artillery, and aircraft) was provided by the Allies (mainly by the French Army). For the Meuse–Argonne front alone, this represented 2,780 artillery pieces, 380 tanks, and 840 planes.

Concerning armored support, the 35th Division was completed by the 1st Tank Brigade (under George S. Patton) with 127 American-crewed Renault FT light tank and 28 French-crewed Schneider medium tanks. The 3rd US Tank brigade with 250 French-crewed tank was also involved supporting the V Corps. The 37th and 79th Division were augmented with a French tank regiment (Renault FT light tank) and 2 groups of medium tank (St-Chamond). The 91st Division was augmented with an equivalent force (1 light tank regiment and 2 groups medium tank).

As the battle progressed, both the Americans and the French brought in reinforcements. Eventually, 22 American divisions participated in the battle at one time or another, representing two full field armies.^[11] Other French forces involved included the 2nd Colonial Corps, under Henri Claudel, which had also fought alongside the AEF at the Battle of Saint-Mihiel earlier in September 1918.

The opposing forces were wholly German. During this period of the war, German divisions procured only 50 percent or less of their initial strength. The 117th Division, which opposed the U.S. 79th Division during the offensive's first phase, had only 3,300 men in its ranks. Morale varied among German units. For example, divisions that served on the Eastern front had high morale, while conversely divisions that had been on the Western front had poor morale. Resistance grew to approximately 200,000–450,000 German troops from the Fifth Army of Group Gallwitz commanded by General Georg von der Marwitz. The Americans estimated that they opposed parts of 44 German divisions overall, though many fewer at any one time.

Objectives

• Pierce the Hindenburg Line: The primary objective of the Allied forces, particularly the AEF under the command of General John J. Pershing, was to breach the heavily fortified Hindenburg Line and advance beyond it. The Hindenburg Line was a series of heavily fortified defensive positions, including trenches, barbed wire entanglements, machine-gun nests, and artillery emplacements, designed to halt any Allied offensive.
• Advance into German Territory: By breaking through the Hindenburg Line, the Allies aimed to penetrate deep into German-held territory, disrupt enemy communication and supply lines, and weaken the German Army's ability to resist further Allied advances. This would also put pressure on Germany's ability to sustain the war effort, potentially hastening the end of the conflict.
• Force Germany to Surrender: The ultimate objective of the Battle of the Argonne Forest, as part of the broader Allied offensive on the Western Front, was to bring about the collapse of the German Army and compel Germany to seek an armistice and end the war. The success of the offensive was critical for achieving this goal and bringing about a decisive victory for the Allies.

First phase (September 26 – October 4, 1918)

The Allies decided to prepare for the assault on September 26 at 02:30 by launching one of the most expensive and stunning artillery barrages. This barrage was done with 2711 artillery guns and helped to destroy obstacles like barbed wire to help the Allies push up more effectively when the assault began. One of these artillery groups was led by Capt. Harry S. Truman, a future US president.^[12] "During the three hours preceding H hour, the Allies expended more ammunition than both sides managed to fire throughout the four years of the American Civil War. The cost was later calculated to have been $180 million, or $1 million per minute (about $3.5 billion in 2022 dollars)."^[13] The American attack began at 05:30 on September 26 with mixed results. The V and III Corps met most of their objectives, but the 79th Division failed to capture Montfaucon, the 28th "Keystone" Division's attack virtually ground to a halt due to formidable German resistance, and the 91st "Wild West" Division was compelled to evacuate the village of Épinonville though it advanced 8 km (5.0 mi). The inexperienced 37th "Buckeye" Division failed to capture Montfaucon d'Argonne.

The subsequent day, September 27 most of the 1st Army failed to make any gains. The 79th Division finally captured Montfaucon and the 35th "Santa Fe" Division captured the village of Baulny, Hill 218, and Charpentry, placing the division forward of adjacent units. On September 29, six extra German divisions were deployed to oppose the American attack, with the 5th Guards and 52nd Division counterattacking the 35th Division, which had run out of food and ammunition during the attack. The Germans initially made significant gains, but were barely repulsed by the 35th Division's 110th Engineers, 128th Machine Gun Battalion, and Harry Truman's Battery D, 129th Field Artillery. In the words of Pershing, "We were no longer engaged in a maneuver for the pinching out of a salient, but were necessarily committed, generally speaking, to a direct frontal attack against strong, hostile positions fully manned by a determined enemy."^[14]

The German counterattack had shattered so much of the 35th Division—a poorly led division, most of whose key leaders had been replaced shortly before the attack, made up of National Guard units from Missouri and Kansas—that it had to be relieved early, though remnants of the division subsequently reentered the battle.^[15] Part of the adjacent French attack met temporary confusion when one of its generals died. Nevertheless, it was able to advance 15 km (9 mi), penetrating deeply into the German lines, especially around Somme-Py (the Battle of Somme-Py (French: Bataille de Somme-Py)) and northwest of Reims (the Battle of Saint-Thierry (French: Bataille de Saint-Thierry)).^[10] The initial progress of the French forces was thus faster than the 3 to 8 km (2 to 5 mi) gained by the adjacent American units, though the French units were fighting in a more open terrain, which can be an easier terrain from which to attack.^[3]

With the US struggling to make the progress they wanted, as well as struggling to pull their logistics together, Pershing ordered a halt to the attack on October 1st. This allowed the Pershing to regroup all the men and reinforce the line. This move to halt the attack was not popular among the Allied Generals and almost lost Pershing his job. Despite the lack of faith in Perishing he was allowed to continue leading the offensive. And The Offensive started up again on October 4th. ^[12]

Second phase (October 4–28, 1918)

The second phase began on October 4, when the first assault divisions (the 91st, 79th, 37th and 35th) were replaced by the 32nd, 3rd and 1st Divisions. The 1st Division created a gap in the lines when it advanced 2.5 km (1.6 mi) against the 37th, 52nd, and 5th Guards Divisions.^[vague] It was during this phase that the Lost Battalion affair occurred. The battalion was rescued by an attack by the 28th and 82nd Divisions (the 82nd attacking soon after taking up its positions in the gap between the 28th and 1st Divisions) on October 7.On October 12 Pershing had to reorganize the AEF and First Army due to the many struggles that were occurring in the second phase including disasters like the lost battalion which reflected badly on Pershing's leadership. Pershing started by dividing the First Army into two smaller armies. The First Army would be led by Hunter Ligget, and the newly formed Second Army would be led by Robert Bullard. Pershing, now free to focus on just the AEF, cleaned out all of the AEF’s senior officers. This was done as Pershing felt the AEF leaders lacked the aggression that was needed in the offensive.^[12] The Americans launched a series of costly frontal assaults that finally broke through the main German defenses (the Krimhilde Stellung of the Hindenburg Line) between October 14–17 (the Battle of Montfaucon (French: Bataille de Montfaucon)). During the Battle of Montfaucon Missouri and Kansas National Guard soldiers were the first U.S. troops who tried to break through the stronghold of the Hindenburg Line at Côte de Châtillon but they were repulsed due to poor leadership. Next, the elite U.S. 1st Infantry Division tried and failed after suffering catastrophic casualties. The Rainbow Division (42nd Division) under Brigadier General Douglas MacArthur was finally able to take Côte de Châtillon after exposing a gap in the German defenses that was discovered by MacArthur's soldiers. This victory at Côte de Châtillon was considered the decisive turning point of the whole Meuse–Argonne offensive.^[16] By the end of October, U.S. troops had advanced ten miles and cleared the Argonne Forest. On their left the French had advanced twenty miles, reaching the Aisne River.^[3] It was during the opening of this operation, on October 8, that Corporal (later Sergeant) Alvin York made his famous capture of 132 German prisoners near Cornay.^[17] On October 23, notable injuries were sustained to Major Frank Cavanaugh as a result of enemy shellfire. From October 27 to November 1 Liggett allowed the Army to reorganize. This was due to the huge number of casualties that First Army had taken, First Army had lost over 9000 men and had over 100,000 men injured since the start of the operation. The First Army needed time to not only train the fresh troops coming in, but also needed time for First Army engineers to build roads and light rails. Liggett wanted to ensure that he had manpower and resources, because that was the advantage they held over the Germans was the ability to reinforce and outnumber.^[12]

Third phase (October 28 – November 11, 1918)

By October 31, the Americans had advanced 15 km (9.3 mi) and had cleared the Argonne Forest. On their left the French had advanced 30 km (19 mi), reaching the River Aisne. The American forces reorganized into two armies. The First, led by General Liggett, moved to the Carignan-Sedan-Mezieres Railroad. The Second Army, led by Lieutenant General Robert L. Bullard, was directed to move eastward toward Metz. The two U.S. armies faced portions of 31 German divisions during this phase. The American troops captured German defenses at Buzancy, allowing French troops to cross the River Aisne, whence they rushed forward, capturing Le Chesne (the Battle of Chesne (French: Bataille du Chesne)).^[18] In the final days, the French forces conquered the immediate objective, Sedan and its critical railroad hub (the Advance to the Meuse (French: Poussée vers la Meuse)), on November 6 and American forces captured surrounding hills. On November 11, news of the German armistice put a sudden end to the fighting.