German Invasion of Belgium (1914) and the Schlieffen Plan

The German invasion of Belgium began on 4 August 1914, when German troops crossed the border of a neutral country to outflank the French army as part of the Schlieffen Plan. Belgium’s decision to resist, the siege of the fortress city of Liège and the killing of civilians that followed shocked international opinion. The invasion was also the immediate reason Britain entered the First World War.

Background: neutrality and the Schlieffen Plan

Belgium had been neutral since its independence. Under the Treaty of London of 1839, Britain, France, Prussia, Austria and Russia guaranteed its neutrality, and Belgium in turn was required to defend it. The country built strong fortress rings around Liège, Namur and Antwerp in the late nineteenth century to deter invasion.

German military planners, however, saw Belgium as the key to a quick victory over France. The plan associated with Alfred von Schlieffen, chief of the general staff until 1906, sent the strong right wing of the German army through Belgium to avoid the fortresses on the Franco-German border. His successor, Helmuth von Moltke the Younger, decided not to cross the Netherlands as well, which made it essential to capture Liège and its railway junctions at once.

The ultimatum

During the July Crisis, on the evening of 2 August 1914, Germany delivered an ultimatum demanding free passage through Belgium within 12 hours and promising compensation. The government of King Albert I rejected it the next morning, declaring that Belgium would defend its neutrality by force.

German troops crossed the border near Gemmenich early on 4 August. That day the British government sent its own ultimatum demanding that Germany respect Belgian neutrality. Bethmann Hollweg reportedly told the British ambassador that Britain was going to war over “a scrap of paper”, a phrase that became famous in British propaganda. When the ultimatum expired at 11 p.m. London time, Britain was at war.

The siege of Liège

Liège was protected by a ring of 12 forts commanded by General Gérard Leman. German infantry attacks on 5–6 August were driven back with heavy losses, but on 7 August a brigade led by Erich Ludendorff, who had taken command after its general was killed, slipped between the forts and entered the city.

The forts themselves held out until the Germans brought up super-heavy siege artillery, including Krupp 42 cm howitzers, nicknamed “Big Bertha”, and Austrian 30.5 cm Škoda mortars. Their shells smashed the concrete and steel of the forts one after another. Leman was captured unconscious in the ruins of Fort de Loncin on 15 August, and the last forts surrendered on 16 August.

The Germans had expected Liège to fall within a couple of days. Instead the forts, built of unreinforced concrete in the 1880s and never fully modernised, held out for well over a week, and their garrisons suffered terribly when the huge shells struck. At Fort de Loncin a shell detonated the magazine on 15 August, killing around 350 of the men inside; many of them still lie in the ruins, which are preserved as a memorial.

Historians debate how much the Belgian defence delayed the German timetable; estimates usually range from a few days to little more than that. But Belgian resistance boosted Allied morale and gave the French and British time to deploy.

The advance and the occupation

The Belgian army, about 117,000 strong in the field, fought delaying actions such as the cavalry battle at Halen on 12 August, then withdrew to the fortress of Antwerp. German troops entered Brussels unopposed on 20 August, and Namur fell on 25 August. The German armies swept on into France, meeting the British at Mons on 23 August, until they were stopped at the First Battle of the Marne.

Antwerp fell on 10 October after a siege, and the Belgian army escaped westwards to the river Yser. There, in late October, it opened the sluices at Nieuwpoort to flood the low-lying land, halting the German advance. For the rest of the war King Albert and the army held a small strip of West Flanders, while the rest of Belgium lived under a harsh German occupation.

Atrocities against civilians

During the invasion German troops killed civilians in hundreds of towns and villages, convinced that Belgian civilians, francs-tireurs, were firing on them. According to the detailed study by John Horne and Alan Kramer, about 6,500 civilians were killed in Belgium and northern France between August and October 1914. They found no evidence of organised civilian resistance; most alleged attacks were confusion, panic or friendly fire.

Among the worst incidents, about 674 civilians were killed at Dinant on 23 August. At Leuven (Louvain), from 25 August, around 248 civilians were killed and much of the town was burned, including the university library with its medieval manuscripts and some 230,000 books. These events were reported around the world and were exaggerated in Allied propaganda, which later made many people doubt even the true stories.

In Britain, the Bryce Report of May 1915, chaired by the former ambassador James Bryce, collected testimony about German atrocities. It mixed genuine evidence with unverified and sensational claims, and after the war its exaggerations fed a widespread belief that the atrocities had been invented. Research since the 1990s, using German as well as Belgian and French archives, has shown that mass killings of civilians did take place, even though many of the most lurid stories were false.

Key people

• King Albert I (1875–1934): led the Belgian army in person and stayed on Belgian soil behind the Yser throughout the war, earning the name of the Soldier King.
• Gérard Leman (1851–1920): commander of the defence of Liège, captured at Fort de Loncin, who spent much of the war as a prisoner in Germany.
• Erich Ludendorff (1865–1937): the staff officer who led the brigade into Liège, then went east to the victory at Tannenberg.
• Theobald von Bethmann Hollweg (1856–1921): German chancellor, who admitted to the Reichstag on 4 August that the invasion was a wrong which Germany would put right after the war.
• Cardinal Désiré-Joseph Mercier (1851–1926): Archbishop of Mechelen, whose pastoral letter Patriotism and Endurance at Christmas 1914 became a symbol of Belgian resistance to the occupation.

Timeline

• 1839, 19 April: the Treaty of London guarantees Belgian neutrality.
• 1914, 2 August: Germany sends Belgium an ultimatum demanding free passage.
• 1914, 4 August: German troops invade Belgium; Britain declares war on Germany.
• 1914, 7 August: German troops enter the city of Liège.
• 1914, 16 August: the last forts of Liège surrender.
• 1914, 20 August: German troops enter Brussels.
• 1914, 25 August: Namur falls; the burning of Leuven begins.
• 1914, 10 October: Antwerp surrenders.
• 1914, late October: Belgian troops flood the Yser plain and halt the German advance.

Consequences

The invasion gave Britain a clear and popular reason to enter the war and shaped Allied propaganda about “poor little Belgium”. Around 1.5 million Belgians fled their homes in 1914; about 250,000 found refuge in Britain, and many more crossed into the Netherlands and France. The occupation brought requisitions, food shortages, deportations of workers and executions, including that of the British nurse Edith Cavell in 1915. The country was ruled by a German governor-general, and in 1916–1917 roughly 120,000 Belgian men were deported for forced labour in Germany or behind the front.

Why it matters

The invasion of Belgium turned a continental war into a world war by bringing in Britain and its empire. It also marked a grim new treatment of civilians in war, and the memory of the atrocities of 1914, long disputed in Germany, has been confirmed by modern research.