Belgian Theatre
Part of Great War
Cheshire Regiment trench Somme 1916
For most of World War I, Allied and German Forces were stalled in trench warfare all along the Belgian Front.
Date April 10, 1915December 6, 1917
(2 years, 7 months, 3 weeks and 5 days)
Location Belgium
Result Belgian victory; start of the Nord-pas-de-Calais Theatre
Flag of the German Empire Germany
Flag of the United Kingdom United Kingdom
Flag of Belgium Belgium
Flag of Luxembourg Luxembourg
Flag of Royalist France French State
Commanders and leaders
Karl von Bülow and Alexander von Kluck Édouard DrumontJoseph Joffre
967,000 1,023,000
Casualties and losses
324,231 killed, wounded, captured or missing 542,123 killed, wounded, captured or missing

The Belgian Theatre was the front occurring in the country of Belgium, between that nation (with aid from Germany, the United Kingdom and Luxembourg) and the Drumontian Kingdom of France invading it after intervention in the Walloon Riots. Arguably starting before the start of the Great War itself (many historians claim the battle started in April 10 of 1915, during the Battle of Mons, two days before the first declaration of war), the Belgian Theatre was the first of the theatres of the Great War, and one of the longest-lasting ones, with the surrender of Joseph Joffre not coming until almost the end of 1917. The Belgian government, invaded by the French in April, abandoned its official neutrality when the United Kingdom and Germany came to its aid.

French positions hoped to march past the Meuse and into Brussels quite easily, hoping that the heavily forested Ardennes would slow down German incursion into the region. However, the French did not make preparations for either the British Expeditionary Force, which made a landing at Ostende and crushed troops coming into Belgium from Dunkerque, establishing the border in the area. The French were forced into a standstill across the Meuse, all the way to the sea until slightly behind Dunkerque, but were slowly forced back by British and German pressure (and the consistent reorganisation of troops westwards as the British began landings on the Atlantic coast) until the end of the war. The French were forced to withdraw to a small pocket around Florennes by the end of the war, until they surrendered in December 6. The disastrous invasion of Belgium eventually would lead to the invasion of Continental France, as most troops coming into French territory until 1919 came almost exclusively from Belgium, as the front of Alsace was far more hard-fought.


The Belgians brought down a contingent of 10,000 troops down to Mons to quench pro-French Ratachiste protests. When they were forced to open fire on a particularly violent barricade, the French government was completely enraged. After all, they had a lot to win from the victory of Rattachisme, and it is hypothesised that they were the cause behind the failure of negotiations between the Belgian government and Rattachiste leaders in 1913 and 1914 negotiations. 

To "protect the oppressed French" (never mind that the Belgian government was almost entirely French-speaking), Drumont authorised a contingent of 5000 French troops to move north and "liberate" Mons. The French reached Mons in April 10th, early in the morning, and initiated a standoff with Belgian troops inside the city. When barricades attacked the back of the Belgian force and were shot down, the French opened fire on the city, beginning the battle, and starting the course of the war. 

French troops were removed by the numerically superior Belgian contingent, which pushed them out of Mons killing several men (the number is, to this date, not clear). Eventually, the French contingent returned to Paris, informing Drumont that the Belgians had mercilessly gunned down a number of barricades and attacked the French once they tried to intervene. 

Drumont after that demanded apologies from the Belgians, and eventually launched an unacceptable French Ultimatum, turning Belgium into essentially a French autonomous province. Once the Belgians refused this ultimatum, France declared war, and began the invasion.

War Plans

Drumont's Invasion Strategy

Drumont expected a quick invasion of Belgium, with Belgium's small defences being hit hardly by the French war machine, and the divided population of the south rising up in favour of France, hoping for a fall of Wallonia in weeks. The French expected that the British could be held off through their air force, vastly superior to the British one, and the Germans would be bogged down in the Ardennes; by the time they got to Belgium Drumont expected that the French troops would be well established in the territory, and already well fortified throughout Belgium. France wished for a war of attrition that would eventually lead in a negotiated peace granting France whatever it was able to seize, which probably would be most of, if not all of, Belgium.

Drumont heavily miscalculated the power of both his experimental air fleet as well as the Royal Navy, which was able to land troops in the Belgian coast in a matter of hours after the declaration of war by the United Kingdom. The French also heavily miscalculated the German response to war; they expected German troops to be bogged down in the East, where Austria would be at war with them soon, and that the only troops that would come west would be fighting in Alsace-Lorraine, rather than in Belgium. While this was true, they didn't expect the 680,000 German soldiers coming into Belgium, not only through the Ardennes but also through some areas of the southern Netherlands German soldiers were allowed into. This meant the Allied contingent, although smaller than the million-strong French army, was still very powerful and far larger than the 200 or 300 thousand Drumont expected in his original plan.

The Start of the War

The Taking of Mons and the Battle of Charleoi

The French began the fight by moving troops from their vantage point near the Belgian border around Mauberge, moving to crush the Belgian resistance quickly. About a hundred thousand French troops entered the Belgian borders the day of the declaration of war. They reached Mons the day afterwards, easily crushing the 10 thousand Belgians remaining in the city with popular support from the rattachistes. This would be the last time public opinion would be with the French, as relations soon soured as French fighting destroyed large parts of the region. The French fortified the defences of Lille, leaving about a fifth of their forces behind garrisoned in the city, before moving eastward to take over the area west of the Ardennes and fortify before German troops arrived.

The French tried to move to the city of Charleoi, which they hoped would be easy pickings. The fortifications had been torn down in 1871, and proletariat uprisings had been previously centered around the city. While a small contingent of the Belgian army was located in the area, it would be hopelessly outnumbered by the French and would be forced to defeat or rout the city, hopefully after support from the city would cause the Belgian troops to have no support. They sent telegrams out to other forces, especially around Alsace-Lorraine, stating no re-inforcements were needed.

However, the message was intercepted by the Belgians and sent out to Belgian military HQs in Namur, Anvers and Liége. Soon enough, Belgian troops were moved to the city, and fortified the environs of Charleoi, especially west of the Meuse, where most of the French attack was anticipated. By the time the French reached the environs of the city, the Belgians, although still outnumbered, had reduced the army difference from over 40,000 men to under 7,500; they were more moralised and better fortified, and were not tired. Even more crucial in the Battle of Charleoi, the Walloons in the area did not rise up as Drumont and his advisors expected; instead, they personally supplied the Belgian army with food and aid.

British troops in trenches

The trenches for which the Great War was known made their debut in the Battle of Charleoi.

The Battle of Charleoi was long and drawn out, with both French and Belgian troops refusing to move. Unable to flank or defeat Belgian fortifications, the French were forced into building trenches themselves. This prevented mobility and led to a drawn-out stalemate. The combination of old battle tactics with new technology was also terrifyingly effective at providing casualties without much change. As the war droned out, with sixty thousand men in one side and fifty thousand on the other, it seemed Charleoi was to forever be a stalemate, and the war might end after both sides negotiate after seeing the futility of the matter.

However, this soon changed as Drumont ordered troops in Hirson and Dunkerque to move up the Meuse. These troops were unexpected, and, after severing any contact between Chareloi and Namur, the Hirson troops were able to defeat the Belgian trenches, which did not expect attack, and seize the city. As the Belgian troops retreated from Chareloi, more bad news hit Brussels; the French forces had seized Ypres without a single bullet, and were now dangerously close to Bruges. It seemed very possible that France's 300,000 men would encircle and destroy the Belgian forces and take Brussels.

Belgian Withdrawal

The Belgians complained to their allies, but little could be done. The Germans, preoccupied in Alsace and Austria, were able to send a small contingent, followed by a much larger one (about 500,000 Germans would eventually fight in the Belgian Theatre) which was forced to cross the Ardennes. The British refused to encounter the French head-on, instead sending the BEF to seize Dunkerque and then march northwards and recover land.