The Hundred Days Offensive (8 August to 11 November 1918) was a series of massive
Allied offensives that ended the
First World War
World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
. Beginning with the
Battle of Amiens (8–12 August) on the
Western Front, the Allies pushed the
Imperial German Army
The Imperial German Army (1871–1919), officially referred to as the German Army (), was the unified ground and air force of the German Empire. It was established in 1871 with the political unification of Germany under the leadership of Kingdom o ...
back, undoing its gains from the
German spring offensive (21 March – 18 July).
The Germans retreated to the
Hindenburg Line, but the Allies broke through the line with a series of victories, starting with the
Battle of St Quentin Canal on 29 September. The offensive led directly to the
Armistice of 11 November 1918 which ended the war with an Allied victory. The term "Hundred Days Offensive" does not refer to a planned Allied campaign, but rather the rapid series of Allied victories.
Background
The
German spring offensive on the
Western Front had begun on 21 March 1918 with
Operation Michael and had petered out by July. The
German Army
The German Army (, 'army') is the land component of the armed forces of Federal Republic of Germany, Germany. The present-day German Army was founded in 1955 as part of the newly formed West German together with the German Navy, ''Marine'' (G ...
had advanced to the
River Marne, but failed to achieve their aim of a victory that would decide the war. When the German ''Operation Marne-Rheims'' ended in July, the Allied supreme commander,
Ferdinand Foch
Ferdinand Foch ( , ; 2 October 1851 – 20 March 1929) was a French general, Marshal of France and a member of the Académie Française and French Academy of Sciences, Académie des Sciences. He distinguished himself as Supreme Allied Commander ...
, ordered a counter-offensive, which became known as the
Second Battle of the Marne. The Germans, recognizing their untenable position, withdrew from the Marne to the north. For this victory, Foch was granted the title
Marshal of France
Marshal of France (, plural ') is a French military distinction, rather than a military rank, that is awarded to General officer, generals for exceptional achievements. The title has been awarded since 1185, though briefly abolished (1793–1804) ...
.
After the Germans had lost their forward momentum, Foch considered the time had arrived for the
Allies to return to the
offensive. General
Pershing who commanded the
American Expeditionary Force
The American Expeditionary Forces (AEF) was a formation of the United States Armed Forces on the Western Front (World War I), Western Front during World War I, composed mostly of units from the United States Army, U.S. Army. The AEF was establis ...
(AEF) was keen to use his army as an independent force. The
British Expeditionary Force (BEF) had been reinforced by large numbers of troops returned from the
Sinai and Palestine campaign and from the
Italian front, and by replacements previously held back in Britain by
Prime Minister
A prime minister or chief of cabinet is the head of the cabinet and the leader of the ministers in the executive branch of government, often in a parliamentary or semi-presidential system. A prime minister is not the head of state, but r ...
David Lloyd George.
[.]
The military planners considered a number of proposals. Foch agreed to a proposal by
Field Marshal
Field marshal (or field-marshal, abbreviated as FM) is the most senior military rank, senior to the general officer ranks. Usually, it is the highest rank in an army (in countries without the rank of Generalissimo), and as such, few persons a ...
Sir Douglas Haig,
commander-in-chief of the BEF, to strike on the
River Somme, east of
Amiens
Amiens (English: or ; ; , or ) is a city and Communes of France, commune in northern France, located north of Paris and south-west of Lille. It is the capital of the Somme (department), Somme Departments of France, department in the region ...
and south-west of the site of the 1916
Battle of the Somme, to force the Germans away from the vital
Amiens
Amiens (English: or ; ; , or ) is a city and Communes of France, commune in northern France, located north of Paris and south-west of Lille. It is the capital of the Somme (department), Somme Departments of France, department in the region ...
–
Paris
Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
railway.
The Somme was chosen because it remained the boundary between the BEF and the French armies, along the Amiens–Roye road, allowing the two armies to cooperate. The
Picardy terrain provided a good surface for
tank
A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and battlefield mobility provided by tracks and a powerful engine; ...
s, unlike in
Flanders
Flanders ( or ; ) is the Dutch language, Dutch-speaking northern portion of Belgium and one of the communities, regions and language areas of Belgium. However, there are several overlapping definitions, including ones related to culture, la ...
, and the defences of the German
2nd Army under General
Georg von der Marwitz were relatively weak, having been subjected to continual raiding by the
Australians
Australians, colloquially known as Aussies, are the citizenship, citizens, nationality, nationals and individuals associated with the country of Australia. This connection may be residential, legal, historical or ethno-cultural. For most Aust ...
in a process termed
peaceful penetration.
Battles
Advance in Picardy
Battle of Amiens
The Battle of Amiens (with the French attack on the southern flank called the Battle of Montdidier) opened on 8 August, with an attack by more than 10 Allied divisions—Australian, Canadian, British, and French forces—with more than 500 tanks.
The mastermind of the plan was the Australian Lieutenant General
John Monash
General (Australia), General Sir John Monash (; 27 June 1865 – 8 October 1931) was an Australian civil engineer and military commander of the World War I, First World War. He commanded the 13th Brigade (Australia), 13th Infantry Brigade befor ...
. Through careful preparation, the Allies achieved surprise.
The attack, led by the British
Fourth Army, broke through the German lines, and tanks attacked German rear positions, sowing panic and confusion. By the end of the day, a gap wide had been created in the German line south of the Somme. The Allies had taken 17,000 prisoners and 339 guns. Total German losses were estimated to be 30,000 men, while the Allies had suffered about 6,500 killed, wounded and missing. The collapse in German morale led
Erich Ludendorff to dub it "the Black Day of the German Army".
The advance continued for three more days but without the spectacular results of 8 August, since the rapid advance outran the supporting artillery and ran short of supplies.
During those three days, the Allies had managed to gain . Most of this was taken on the first day as the arrival of German reinforcements after this slowed the Allied advance.
On 10 August, the Germans began to pull out of the
salient that they had managed to occupy during Operation Michael in March, back towards the
Hindenburg Line.
Somme

Haig refused to continue the attack and instead prepared to launch a fresh offensive by the
Third Army at
Albert (the
Battle of Albert), which opened on 21 August.
The offensive was a success, pushing the German 2nd Army back over a front. Albert was captured on 22 August.
The attack was widened on the south, by the French
Tenth Army starting the Second Battle of Noyon on 17 August, capturing the town of
Noyon on 29 August.
On 26 August, to the north of the initial attack, the
First Army widened the attack by another with the Second Battle of Arras of 1918.
Bapaume fell on 29 August (during the
Second Battle of Bapaume).
Advance to the Hindenburg Line
With the front line broken, a number of battles took place as the Allies forced the Germans back to the Hindenburg Line. East of Amiens (after the
Battle of Amiens), with artillery brought forward and munitions replenished, the Fourth Army also resumed its advance, with the Australian Corps crossing the Somme River on the night of 31 August, breaking the German lines during the
Battle of Mont Saint-Quentin. On 26 August, to the north of the Somme, the First Army widened the attack by another with the Second Battle of Arras of 1918, which includes the
Battle of the Scarpe (1918) (26 August) and the
Battle of Drocourt-Queant Line (2 September).
South of the BEF, the French
First Army approached the Hindenburg Line on the outskirts of St. Quentin during the Battle of Savy-Dallon (10 September),
and the French Tenth Army approached the Hindenburg Line near
Laon during the Battle of Vauxaillon (14 September).
The British Fourth Army approached the Hindenburg Line along the St Quentin Canal, during the
Battle of Épehy (18 September). By 2 September, the Germans had been forced back close to the Hindenburg Line from which they had launched their offensive in the spring.
Battles of the Hindenburg Line

Foch planned a series of
concentric attacks on the German lines in France (sometimes referred to as the Grand Offensive), with the various axes of advance designed to cut German
lateral communications, intending that the success of an attack would enable the entire front line to be advanced.
The main German defences were anchored on the Hindenburg Line, a series of defensive fortifications stretching from
Cerny on the
Aisne
Aisne ( , ; ; ) is a French departments of France, department in the Hauts-de-France region of northern France. It is named after the river Aisne (river), Aisne. In 2020, it had a population of 529,374.
Geography
The department borders No ...
river to
Arras
Arras ( , ; ; historical ) is the prefecture of the Pas-de-Calais department, which forms part of the region of Hauts-de-France; before the reorganization of 2014 it was in Nord-Pas-de-Calais. The historic centre of the Artois region, with a ...
.
Before Foch's main offensive was launched, the remaining German salients west and east of the line were crushed at
Havrincourt and
St Mihiel on 12 September and at the Battle of Épehy and the
Battle of the Canal du Nord on 27 September.
The first attack of the Grand Offensive was launched on 26 September by the French and the AEF in the
Meuse-Argonne Offensive (this offensive includes the battles of Somme-Py, Saint-Thierry, Montfaucon, and Chesne of 1 November). On 28 September, the Army Group under
Albert I of Belgium
Albert I (8 April 1875 – 17 February 1934) was King of the Belgians from 23 December 1909 until his death in 1934. He is popularly referred to as the Knight King (, ) or Soldier King (, ) in Belgium in reference to his role during World War I ...
(the Belgian Army, the British
Second Army and the
French Sixth Army), attacked near
Ypres in Flanders (the
Fifth Battle of Ypres). Both attacks made good progress initially but were then slowed by supply difficulties. The Grand Offensive involved attacking over difficult terrain, resulting in the Hindenburg Line not being broken until 17 October.
On 29 September, the central attack on the Hindenburg Line commenced, with the British Fourth Army (with British, Australian and American forces) attacking in the
Battle of St Quentin Canal and the French First Army attacking fortifications outside St Quentin. By 5 October, the Allies had broken through the entire depth of the Hindenburg defences over a front.
General Rawlinson wrote, "Had the Boche
ermansnot shown marked signs of deterioration during the past month, I should never have contemplated attacking the Hindenburg line. Had it been defended by the Germans of two years ago, it would certainly have been impregnable…."
On 8 October, the First and Third British Armies broke through the Hindenburg Line at the
Second Battle of Cambrai. This collapse forced the German High Command to accept that the war had to be ended. The evidence of failing German morale also convinced many Allied commanders and political leaders that the war could be ended in 1918; previously, all efforts had been concentrated on building up forces to mount a decisive attack in 1919.
Subsequent operations

Through October, the German armies retreated through the territory gained in 1914. The Allies pressed the Germans back toward the lateral railway line from
Metz
Metz ( , , , then ) is a city in northeast France located at the confluence of the Moselle (river), Moselle and the Seille (Moselle), Seille rivers. Metz is the Prefectures in France, prefecture of the Moselle (department), Moselle Departments ...
to
Bruges, which had supplied the front in northern France and Belgium for much of the war. As the Allied armies reached this line, the Germans were forced to abandon increasingly large amounts of heavy equipment and supplies, further reducing their morale and capacity to resist.
The Allied and German armies suffered many casualties. Rearguard actions were fought during the
Pursuit to the Selle (9 October), battles of
Courtrai
Kortrijk ( , ; or ''Kortrik''; ), sometimes known in English as Courtrai or Courtray ( ), is a Belgian city and municipality in the Flemish province of West Flanders.
With its 80,000 inhabitants (2024) Kortrijk is the capital and largest cit ...
(14 October),
Mont-d'Origny (15 October),
the Selle (17 October),
Lys and Escaut (20 October) (including the subsidiary battles of the Lys and of the Escaut), the
Serre (20 October),
Valenciennes (1 November),
the Sambre (including the Second Battle of Guise) (4 November), and Thiérache (4 November), and the
Passage of the Grande Honnelle (5 November), with fighting continuing until the
Armistice
An armistice is a formal agreement of warring parties to stop fighting. It is not necessarily the end of a war, as it may constitute only a cessation of hostilities while an attempt is made to negotiate a lasting peace. It is derived from t ...
took effect at 11:00 on 11 November 1918. The last soldier to die was
Henry Gunther, one minute before the armistice came into effect.
See also
*
Canada's Hundred Days
Notes
References
Bibliography
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External links
* Lloyd, Nicholas
Hundred Days Offensive in
*
ttp://maps.omniatlas.com/europe/19180920/ Maps of Europe during the Allied Hundred Days Offensive at omniatlas.com
{{DEFAULTSORT:Hundred Days Offensive
Conflicts in 1918
1918 in France
1918 in Belgium
Battles of the Western Front (World War I)
Battles of World War I involving Australia
Battles of World War I involving Belgium
Battles of World War I involving British India
Battles of World War I involving Canada
Battles of World War I involving France
Battles of World War I involving New Zealand
Battles of World War I involving Newfoundland
Battles of World War I involving Portugal
Battles of World War I involving South Africa
Battles involving Thailand
Battles of World War I involving the United Kingdom
Battles of World War I involving the United States
Military operations of World War I involving Germany
Military operations of World War I involving chemical weapons
Wilhelm, German Crown Prince
Paul von Hindenburg
Philippe Pétain