The Main Phases of the War, 1914–1918

1A short war that lasted four years

In August 1914 every general staff planned for a short war. German planners gave themselves about six weeks to defeat France; French plans aimed at a rapid offensive into Alsace-Lorraine. The war actually lasted from 28 July 1914 to 11 November 1918, four years and three months, and on the Western Front the armies spent most of that time within a few kilometres of the lines they held at the end of 1914. Explaining that gap between plan and reality is the main analytical task of this lesson. The diagram divides the war into three phases; notice that the middle phase is the longest.

2Phase 1, 1914: why the war of movement failed

The Schlieffen Plan, as modified by the chief of the German general staff, Helmuth von Moltke, sent German armies through Belgium to encircle Paris. It failed for several connected reasons:

• Belgian resistance at Liège and the British Expeditionary Force at Mons (23 August) delayed the German right wing.
• Russia mobilised faster than expected and invaded East Prussia, so Moltke moved two army corps to the east.
• The marching troops, supplied by horse-drawn wagons once they left the railways, were exhausted; the German First Army turned east of Paris instead of round it.
• French and British counter-attacks on the Marne (5–12 September) forced the Germans back to the River Aisne, where they dug in.

Each side then tried to outflank the other to the north, the "race to the sea", until the lines reached the Channel coast. After the First Battle of Ypres (October–November) a continuous line of trenches ran about 700 km from the Belgian coast to the Swiss border. In the east the Germans destroyed a Russian army at Tannenberg (26–30 August), but Austria-Hungary was defeated by Russia in Galicia and failed to conquer Serbia. The Ottoman Empire entered the war on Germany's side at the end of October.

3Phase 2, 1915–1917: stalemate and attrition

Why defence was stronger than attack. Machine guns, barbed wire and quick-firing artillery could stop infantry crossing open ground. Railways let a defender bring up reserves faster than an attacker could advance on foot over shell-torn ground. Once attackers had crossed the enemy's front line, telephone wires were cut and there was no portable radio, so commanders could not see or steer the battle.

How each side tried to break the deadlock:

The cost. On 1 July 1916, the first day of the Somme, the British army suffered about 57,000 casualties, about 19,000 of them killed, according to Britain's official history of the war. Verdun cost each side an estimated 330,000 to 380,000 men killed, wounded, missing or captured. The whole Somme battle is estimated to have cost the two sides together more than a million casualties.

1917, the year of crisis. After the failure of the Nivelle Offensive in April, parts of the French army refused to attack (May–June). Russia fell into revolution: the Tsar abdicated in March, and the Bolsheviks seized power in November and asked for an armistice. In October the Italians were routed at Caporetto. The one great gain for the Allies was the entry of the United States, whose army would take a year to arrive in strength.

4Phase 3, 1918: how the deadlock was broken

• Germany's gamble. The Treaty of Brest-Litovsk (3 March 1918) ended the war with Russia and freed German divisions for the west. Ludendorff's Spring Offensive, from 21 March, used short bombardments and small "storm troop" units that bypassed strong points. It advanced further than any attack since 1914, but it exhausted the best German units and left them holding long, exposed lines.
• Allied unity and American manpower. In spring 1918 the French general Ferdinand Foch was made supreme co-ordinator, then commander, of the Allied armies. By the autumn more than a million American soldiers were in France.
• Combined arms. At Amiens on 8 August the British and French, with Australian and Canadian troops, attacked with infantry, tanks, aircraft and accurately aimed artillery working together. Ludendorff later called it the "black day" of the German army. In the "Hundred Days" that followed, the Allies broke the Hindenburg Line.
• Collapse of the Central Powers. Bulgaria signed an armistice on 29 September, the Ottoman Empire on 30 October and Austria-Hungary on 3 November. Sailors mutinied at Kiel, revolution spread in Germany, and Wilhelm II abdicated on 9 November. The armistice was signed in a railway carriage at Compiègne at 5 a.m. on 11 November 1918 and came into force at 11 a.m.

5Lions led by donkeys? The debate on the generals

For much of the twentieth century the British generals, Haig above all, were remembered as callous men who sent soldiers to die in hopeless attacks. The phrase "lions led by donkeys" was made popular by the historian Alan Clark's book The Donkeys (1961). Since the 1990s historians such as Gary Sheffield (Forgotten Victory, 2001) have argued instead for a "learning curve": commanders faced a new kind of war with no radio and untested weapons, learned from costly failures such as the Somme, and by 1918 had built the army that won the Hundred Days. Critics reply that the learning was too slow and paid for in hundreds of thousands of lives. A strong answer uses both views and evidence from particular battles.