The Hundred Days Offensive was a World War I offensive by the Allies against the Central Powers on the Western Front from 1918-08-08 to 1918-11-11 . The offensive was the final straw for the battered German armies which surrendered and deserted in large numbers. The offensive led to the retreat of the German armies and the end of World War I.

Background

The great German offensives on the Western Front beginning with Operation Michael in March 1918 had petered out by July, having advanced to the Marne River, but failed to achieve a decisive breakthrough. When Operation Marne-Rheims petered out in July, the Allied supreme commander, French Field Marshal Ferdinand Foch, ordered a counter-offensive which became the Second Battle of the Marne. The Germans, recognising their untenable position, withdrew from the Marne to the north.

Foch now considered the time had arrived for the Allies to return to the offensive and agreed on a proposal by the commander of the British Expeditionary Force (BEF), Field Marshal Douglas Haig, to strike on the Somme, east of Amiens and southwest of the 1916 battlefield of the Battle of the Somme.

The Somme was chosen as a suitable site for the offensive for a number of reasons. As in 1916, it marked the boundary between the BEF and the French armies, in this case defined by the Amiens-Roye road, allowing the two armies to cooperate. Also the Picardy countryside provided a good surface for tanks, which was not the case in Flanders. Finally, the German defences, manned by the German Second Army of General Georg von der Marwitz , were relatively weak, having been subjected to continual raiding by the Australians in a process termed Peaceful Penetration .

Amiens

Main article: Battle of Amiens

The Battle of Amiens opened on 1918-08-08 with an attack by 10 divisions with more than 500 tanks. The attack broke through the German lines and armoured vehicles attacked German rear positions, sowing panic and confusion. By the end of the day, a gap 15 miles (25 km) long had been punched in the German line south of the Somme. The Allies had taken 17,000 prisoners and captured 330 guns. Total German losses were estimated to be 30,000 on 8 August while the Allies suffered about 6,500 killed, wounded and missing.

The advance continued for three more days but without the spectacular results of 8 August as the rapid progress had outrun the supporting artillery. On 10 August the Germans began to pull out of the salient they had occupied in Operation Michael in March and back towards the Hindenburg Line.

Somme

Main article: Second Battle of the Somme (1918)

On 1918-08-15 , Haig called an end to the offensive south of the Somme and began to plan for an offensive at Albert. That offensive opened on 1918-08-21 . Some 130,000 American troops were involved, along with soldiers from the British third and fourth armies. The offensive was an overwhelming success, pushing the German second army back over a fifty-five kilometre front. Albert was captured in 22 August, Bapaume on August 29, and Péronne on 31 August. By September 2, the Germans had been forced back to the Hindenburg Line.

Breaking the Hindenburg Line

Main articles: Meuse-Argonne Offensive

The Hindenburg Line, a series of German defensive fortifications stretching from Cerny on the Aisne River to Arras, was broken by a series of Allied offensives in September and October.

First, the remaining German salients west of the line were crushed in battles at Havrincourt and St Mihiel on 1918-09-12 , Epehy and Canal du Nord on 1918-09-18 .

Then on 1918-09-26 260,000 soldiers of the American Expeditionary Force went "over the top" in the Meuse-Argonne Offensive north of Verdun. All divisions were successful in capturing their initial objectives, except the 79th division of the AEF. They met stiff resistance at Montfaucon and were unable to progress. This failure allowed the Germans to recover and regroup. Casualties were heavy in the AEF, but even heavier in the German Fifth Army, and on 1918-10-14 American soldiers had penetrated the Hindeburg Line.

To the north the Allies penetrated the Hindenburg Line along the St Quentin Canal on 1918-09-26 , and at Beaurevoir and Cambrai early in October.

Pursuit

Through October the German armies were forced back through the territory gained in 1914. The retreat never turned into a rout. There were rearguard actions at Ypres, Courtrai, Selle , Valenciennes, Sambre and Mons, with fighting continuing until the last minutes before the Armistice with Germany took effect at 11:00 on 1918-11-11 .