World War II military campaign
The invasion of Belgium or Belgian campaign (10–28 May 1940), often referred to within Belgium as the 18 Days' Campaign (; ), formed part of the larger Battle of France, an offensive campaign by Germany during the Second World War. It took place over 18 days in May 1940 and ended with the German occupation of Belgium following the surrender of the Belgian Army.
On 10 May 1940, Germany invaded Luxembourg, the Netherlands, and Belgium under the operational plan "Fall Gelb" (Case Yellow). The Allied armies attempted to halt the German Army in Belgium, believing it to be the main German thrust. After the French had fully committed the best of the Allied armies to Belgium between 10 and 12 May, the Germans enacted the second phase of their operation, a break-through, or sickle cut, through the Ardennes, and advanced toward the English Channel. The German Army ("Heer") reached the Channel after five days, encircling the Allied armies. The Germans gradually reduced the pocket of Allied forces, forcing them back to the sea. The Belgian Army surrendered on 28 May 1940, ending the battle.
The Battle of Belgium included the first tank battle of the war, the Battle of Hannut. It was the largest tank battle in history at the time but was later surpassed by the battles of the North African Campaign and the Eastern Front. The battle also included the Battle of Fort Eben-Emael, the first strategic airborne operation using paratroopers ever attempted.
The German official history stated that in the 18 days of bitter fighting, the Belgian Army were tough opponents, and spoke of the "extraordinary bravery" of its soldiers. The Belgian collapse forced the Allied withdrawal from continental Europe. The British Royal Navy subsequently evacuated Belgian ports during Operation Dynamo, allowing the British Expeditionary Force (BEF), along with many Belgian and French soldiers, to escape capture and continue military operations. France reached its own armistice with Germany in June 1940. Belgium was occupied by the Germans until the autumn of 1944, when it was liberated by the Western Allies.
Pre-battle plans.
Belgium's strained alliances.
The Belgian strategy for a defence against German aggression faced political as well as military problems. In terms of military strategy, the Belgians were unwilling to stake everything on a linear defence of the Belgian–German border, in an extension of the Maginot Line. Such a move would leave the Belgians vulnerable to a German assault in their rear, through an attack on the Netherlands. Such a strategy would also rely on the French to move quickly into Belgium and support the garrison there.
Belgium was wary of continuing its alliance with France. Marshal Philippe Pétain had suggested a French strike at Germany's Ruhr area using Belgium as a spring-board in October 1930 and again in January 1933. Belgium feared it would be drawn into a war regardless, and sought to avoid that eventuality. The Belgians also feared being drawn into a war as a result of the French–Soviet pact of May 1935. The Franco-Belgian agreement stipulated Belgium was to mobilise if the Germans did, but what was not clear was whether Belgium would have to mobilise in the event of a German invasion of Poland.
The Belgians much preferred an alliance with the United Kingdom. The British had entered the First World War in response to the German violation of Belgian neutrality. The Belgian Channel ports had offered the German Imperial Navy valuable bases, and such an attack would offer the German "Kriegsmarine" and the "Luftwaffe" bases to engage in strategic offensive operations against the United Kingdom in the coming conflict. However, the British government paid little attention to the concerns of the Belgians. The lack of this commitment ensured the Belgian withdrawal from the Western Alliance, the day before the remilitarisation of the Rhineland. The lack of opposition to the remilitarisation served to convince the Belgians that France and Britain were unwilling to fight for their own strategic interests, let alone Belgium's. The Belgian General Staff was determined to fight for its own interests, alone if necessary.
Belgian place in Allied strategy.
The French government was infuriated at King Leopold III's open declaration of neutrality in October 1936. The French Army saw its strategic assumptions undermined; it could no longer expect cooperation from the Belgians in defending Belgium's eastern borders, which would allow it to stop a German attack well forward of the French border. The French were dependent on cooperation from the Belgians. Such a situation deprived the French of any prepared defences in Belgium to forestall an attack, a situation which the French had wanted to avoid as it meant engaging the German Panzer divisions in a mobile battle. The French considered invading Belgium immediately in response to a German attack on the country. The Belgians, recognising the danger posed by the Germans, secretly made their own defence policies, troop movement information, communications, fixed defence dispositions, intelligence and air reconnaissance arrangements available to the French military attaché in Brussels. Officially, the Belgian government retained a suspicious posture towards France, considering them as equal a danger to Belgian sovereignty as the Third Reich. French forces were not allowed to enter Belgium, even when the German plans to invade became imminent.
The Allied plan to aid Belgium was the Dyle Plan; the cream of the Allied forces, including French armoured divisions, would advance to the Dyle river in response to a German invasion. The choice of an established Allied line lay in either reinforcing the Belgians in the east of the country, at the Meuse–Albert Canal line, and holding the Scheldt Estuary, thus linking the French defences in the south with the Belgian forces protecting Ghent and Antwerp, seemed to be the soundest defensive strategy.
The weakness of the plan was that it abandoned most of eastern Belgium to the Germans. Militarily it would put the Allied rear at right angles to the French frontier defences; while for the British, with their communications located at the channel ports, would be parallel to their front. Despite the risk of committing forces to central Belgium and an advance to the Scheldt or Dyle lines, which would be vulnerable to an outflanking move, Maurice Gamelin, the French commander, approved the plan and it remained the Allied strategy at the outbreak of war.
The British, with no army in the field and behind in rearmament, were in no position to challenge French strategy, which had assumed the prominent role of the Western Alliance. Having little ability to overrule the French, the British strategy for military action came in the form of strategic bombing of the Ruhr industry.
Belgian military strategy.
On the official Belgian withdrawal from the Western Alliance, the Belgians refused to engage in any official staff meetings with French or British military staff for fear of compromising their neutrality. The Belgians did not regard a German invasion as inevitable and were determined that if an invasion did take place it would be effectively resisted by new fortifications such as Eben Emael.
The Belgians had taken measures to reconstruct their defences along their border with Germany upon Adolf Hitler's rise to power in January 1933. The Belgian government had watched with increasing alarm the German withdrawal from the League of Nations, its repudiation of the Treaty of Versailles and its violation of the Locarno Treaties. The government modernised fortifications at Namur and Liège, and established new lines of defence along the Maastricht–'s-Hertogenbosch canal, joining the Meuse, the Scheldt and the Albert Canal. Protection of the eastern frontier, based mainly on destroying a number of roads, was entrusted to new formations (frontier cyclist units and the newly formed "Chasseurs Ardennais"). By 1935, the Belgian defences were completed. Even so, it was felt that the defences were no longer adequate. A significant mobile reserve was needed to guard the rear areas, and as a result it was considered that the protection against a sudden assault by German forces was not sufficient. Significant manpower reserves would also be needed, but the public rejected a bill to require longer military service and training was rejected on the basis that it would increase Belgium's military commitments, perhaps in conflicts far from home.
King Leopold III made a speech on 14 October 1936 before the Council of Ministers to persuade the people and their government that Belgium's defences needed strengthening. He outlined three main military points for Belgium's increased rearmament:
a) German rearmament and the complete re-militarisation of Italy and Russia had caused most other states, even pacifists like Switzerland and the Netherlands, to take exceptional precautions.
b) Vast changes in military methods, particularly in aviation and mechanization, meant that initial operations could now be of alarming force, speed and magnitude.
c) The lightning reoccupation of the Rhineland came with bases for the start of a possible German invasion moving close to the Belgian frontier.
On 24 April 1937, the French and British publicly declared that Belgium's security was paramount to the Western Allies and that they would defend their borders against aggression of any sort, whether directed solely at Belgium, or to obtain bases to wage war against "other states". The British and French released Belgium from her Locarno obligations to render mutual assistance in the event of German aggression toward Poland, while the British and French maintained their military obligations to Belgium.
Militarily, the Belgians considered the "Wehrmacht" stronger than the Allies, and that engaging in overtures to the Allies would make Belgium a battleground without adequate allies.
The Belgians and French remained confused about what was expected of whom if or when hostilities commenced. The Belgians were determined to hold the border fortifications along the Albert Canal and the Meuse, without withdrawing, until the French Army arrived to support them. Gamelin was not keen on pushing his Dyle plan that far. He was concerned that the Belgians would be driven out of their defences and would retreat to Antwerp, as in 1914. In fact, the Belgian divisions protecting the border were to withdraw and retreat southward to link up with French forces. This information was not given to Gamelin.
As far as the Belgians were concerned, the Dyle Plan had advantages. Instead of the limited Allied advance to the Scheldt, or meeting the Germans on the Franco-Belgian border, the move to the Dyle river would reduce the Allied front in central Belgium by , freeing more forces for use as a strategic reserve. Belgium felt this would save more Belgian territory, in particular the eastern industrial regions. It also had the advantage of absorbing Dutch and Belgian Army formations (including some 20 Belgian divisions). Gamelin justified the Dyle Plan after the defeat using these arguments.
On 10 January 1940, in an episode known as the Mechelen Incident, German Army major, Hellmuth Reinberger, crash-landed in a Messerschmitt Bf 108 near Mechelen-aan-de-Maas. Reinberger was carrying the first plans for the German invasion of western Europe which, as Gamelin had expected, entailed a repeat of the 1914 Schlieffen Plan and a German thrust through Belgium (which was expanded by the "Wehrmacht" to include the Netherlands) and into France.
The Belgians suspected a ruse, but the plans were taken seriously. Belgian intelligence and the military attaché in Cologne correctly suggested the Germans would not commence the invasion with this plan. It suggested that the Germans would try an attack through the Belgian Ardennes and advance to Calais to encircle the Allied armies in Belgium. The Belgians correctly predicted that the Germans would attempt a "Kesselschlacht" (literally "cauldron battle", meaning encirclement), to destroy its enemies. The Belgians had predicted the exact German plan as offered by Erich von Manstein.
The Belgian high command warned the French and British of their concerns. They feared that the Dyle plan would put not just the Belgian strategic position in danger, but also the entire left wing of the Allied front. King Leopold and General Raoul Van Overstraeten, the King's "aide de camp", warned Gamelin and the French Army command of their concerns on 8 March and 14 April. They were ignored.
Belgian plans for defensive operations.
The Belgian plan, "in the event of German aggression" [italics in original] provided for:
(a) A delaying position along the Albert Canal from Antwerp to Liège and the Meuse from Liège to Namur, which was to be held long enough to allow French and British troops to occupy the line Antwerp–Namur–Givet. It was anticipated that the forces of the guarantor Powers would be