Battle of Gembloux (1940)

The Battle of Gembloux (or Battle of the Gembloux Gap) was fought between French and German forces in May 1940 during the Second World War. On 10 May 1940, The Nazi Wehrmacht, invaded Luxembourg, The Netherlands and Belgium under the operational plan Fall Gelb (Case Yellow). Allied armies responded with the Dyle Plan (Breda variant), intended to halt the Germans in Belgium, believing it to be the main German thrust. The Allies committed their best and most mobile to an advance into Belgium on 10 May and on 12 May, the Germans began the second part of Fall Gelb, the Manstein Plan an advance through the Ardennes, to reach the English Channel and cut off the Allied forces in Belgium.

Unaware that the German invasion of the Low Countries was a decoy, the French Army intended to halt the German advance into central Belgium and France on two defensive positions at the towns of Hannut and Gembloux. The French First Army, the most powerful Allied army, was to defend the Gembloux–Wavre axis. The French Corps de Cavalerie (Général René Prioux), advanced to Hannut, to screen the deployment of the rest of the First Army at Gembloux, by delaying a German advance.

After the Battle of Hannut, some 35 km (22 mi) to the north-east, the French retired towards Gembloux and the principal defensive position for the French on the Belgian front. For two days French defeated attacks by elements of the 6th Army. The German surprise attack through the Ardennes and the crossing of the Meuse at Sedan, forced the First Army to retreat from Gembloux, then back over the French frontier towards Lille. The retreat disorganised the Allied defence on the central sector of the Belgian front and the German armies occupied central Belgium. Strategically the battle was inconclusive, it diverted the First Army from Sedan, which allowed the Germans to achieve the strategic goals of Fall Gelb but the First Army survived and during the Siege of Lille diverted German forces from the Battle of Dunkirk, which allowed the British Expeditionary Force and a substantial French contingent to escape.

Between industrial northern France and Paris and the industrial Rhine-Ruhr River basin of Germany, the plain of central Belgium was a natural route of invasion. A ridge running roughly north-east to south-west through the Gembloux area forms a watershed, to the west streams flow into the Escaut (Scheldt) River and to the east into the Meuse (Maas) the area has few natural obstacles and is called the Gembloux Gap (Trouée de Gembloux).

The strategy, operational methods and tactics of the German Army and Luftwaffe have often been labelled "Blitzkrieg" (Lightning War). The concept is controversial and is connected to the problem of the nature and origin of "Blitzkrieg" operations, of which the 1940 campaign is often described as a classic example. An essential element of "Blitzkrieg" was considered to be a strategic, or series of operational developments, executed by mechanised forces to cause the collapse of the defenders' armed forces. "Blitzkrieg" has also been looked on as a revolutionary form of warfare but its novelty and its existence have been disputed. Rapid and decisive victories had been pursued by armies well before the Second World War. In the German wars of unification and First World War campaigns, the German General Staff had attempted Bewegungskrieg (war of manoeuvre), similar to the modern perception of "Blitzkrieg", with varying degrees of success. During the First World War, these methods had achieved tactical success but operational exploitation was slow as armies had to march beyond railheads. The use of tanks, aircraft, motorised infantry and artillery, enabled the Germans to attempt Bewegungskrieg with a faster tempo in 1940, than that of the slow-moving armies of 1914. The internal combustion engine and radio communication solved the problem of operational-level exploitation.

The term "Blitzkrieg" is seen as an anomaly, since there was no explicit reference to such strategy, operations or tactics in German battle plans. There is no evidence in German strategic, military or industrial preparations implying the existence of a thought-out "Blitzkrieg" tendency. Evidence suggests that in 1939 and 1940 the German Reich was preparing the war economy for a war of attrition, not a quick war of manoeuvre, although there was no total economic mobilisation for the war. Hitler's miscalculations in 1939 forced him into war before the war economy was ready and under these circumstances, the German General Staff reverted Vernichtungsgedanke, attempting to win a war quickly, with swift attacks on the flanks and rear of opposing armies, leading to their destruction before the economic and material superiority of the Allies became overwhelming. It was only after the defeat of France in 1940, that the German military intentionally pursued a "Blitzkrieg"-kind of warfare to achieve its ambitions in Europe. In 2005, Karl-Heinz Frieser echoed Matthew Cooper in 1978, who had called "Blitzkrieg" a myth and that it was the weakness of German enemies not the strength of the German army, which had led to the devastating German victories early in the war. Frieser wrote:

The campaign in the west was not a planned campaign of conquest. Instead, it was an operational act of despair to get out of a desperate strategic situation. What is called "Blitzkrieg thinking" did not develop until after [author's emphasis] the campaign in the west. It was not the cause but rather the consequence of victory. Something that in May 1940, had come off successfully to everyone's surprise, was now to serve the implementation of Hitler's visions of conquest in the form of the secret success.

French doctrine emanated from its experiences in the First World War. With only half the population and a third of the industry of Germany, France had suffered proportionally a much higher loss, especially in those killed or permanently disabled. French doctrine therefore rested on the idea of a battle carefully controlled by senior commanders to reduce losses. Doctrine relied on defence in depth, keeping mobile forces away from enemy fire and to secure the line against incursions of enemy armour. The defence of the infantry division on open terrain was based on the artillery which would directly support the infantry and tanks; heavier pieces were reserved for use by the senior commander to make his personal intervention felt on the battlefield. Infantry was to be disposed in depth: from 15 percent to 30 percent of a division's infantry strength in outposts on commanding ground before the main position to cover it from surprises, then the main position of resistance along a natural or artificial terrain obstacle covered by the general barrage of infantry and anti-tank weapons, this position to be some 2 km (1.2 mi) deep down to a stop-line where an anti-tank screen was to be located. Units were to be emplaced on commanding terrain in closed positions capable of defence in all directions, covering the intervals between them with cross fire. Behind the stop-line would be reserves, the divisional reconnaissance battalion and the artillery battery positions in closed strong points. Defence against tanks was a priority throughout the depth of the position. A division on open terrain would hold a front 6–7 km (3.7–4.3 mi) wide and some 5 km (3.1 mi) deep.