10 May – 4 June 1940 

The Fuhrer Directive

Sickle Cut

The German invasion of France can be separated into two phases: The first phase titled Fall Gelb, (Case Yellow) – also known as the Manstein Plan (after its planner Field Marshal Erich von Manstein) or Operation Sichelschnitt (Sickle Cut), was the invasion of France and the Low Countries, in which it was anticipated the Allied forces would be forced back, isolated or destroyed, with German forces acquiring large amounts of territory. The second phase – Fall Rot (Case Red) – was to take place two months later and secure the German positions and eliminate any remaining opposition.

The first phase – originally planned by General Franz Halder - was designed to push the French (and British Expeditionary Force) forces back from their pre-established strongholds – primarily by using Blitzkrieg tactics – to the Somme River in Northern France (which was similar to the events on the Western Front in the First World War.) 

The evolution of Plan/Case Yellow (Fall Gelb) in the lead up to the Invasion of France and the Low Countries.

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However, after the events of the Mechelen Incident, in which a German aircraft carrying a copy of the plans crash landed in France, the plan was revised by Manstein, and it was instead decided that the Germans would attack through the thickly forested Ardennes region – a feat which the French considered near impossible due to the terrain. General Philippe Pétain declared the Ardennes to be "impenetrable" as long as "special provisions" were taken to destroy an invasion force as it emerged from the Ardennes by a pincer attack.

The French held war exercises in 1938, carrying out a hypothetical German armoured attack in this region and it reinforced their belief that the Ardennes – along with the additional obstacle of the Meuse River – made this region virtually impregnable as any real German attack would be delayed enough to allow the French to bring up reinforcements.

German JU-87D 'Stuka' dive bombers in action during the Battle of France. These aircraft caused chaos, inflicting heavy casualties on retreating troops and fleeing civilians.

Planning the attack

By 1940, Germany had mobilised over 4 million men for the Heer (Army), a million for the Luftwaffe (air force) and just under two hundred thousand for the Kriegsmarine (Navy). Additionally, the Waffen-SS now numbered 100,000.

For Fall Gelb, the Germans had allocated around 3 million men, formed into 157 divisions. 135 of these divisions were to be used in the offensive, including 42 reserve divisions. The Germans had almost 2,500 tanks and over 7000 artillery pieces allocated as well.

German soldiers struggle to move a heavy artillery piece, 1940.

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However, despite the impressive sounding figures, there were many issues with the German military. Almost half the German army was at least 40 years old and half of all the soldiers only had a few weeks training. And despite the perception of an efficient, modern German war machine, only ten percent of it was fully motorised with only 120,000 vehicles, which sounds a lot but was less than half of what the French had. And although smaller, all the British Expeditionary Force (BEF) was motorised.

In summary, only half of the German divisions available in 1940 were fully fit for operations and were generally less well-equipped than the Allied armies, or indeed the German armies of the First World War. It would be more accurate to describe it as ‘semi-motorised’, as the small number of well-equipped divisions were offset by a large amount of second or even third-rate divisions.

German motorised units in France.

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When operating at their best though, the Germans made good use of combined arms operations - mobile offensive units, artillery, infantry, engineer, and tanks, all integrated into Panzer divisions to work as a cohesive unit. These Panzer divisions were supported by infantry and motorised divisions who had been trained to work with them.

They also made excellent use of wireless communications: Each tank had radio receivers, allowing them to be directed quickly during a battle and react swiftly to changing situations, conduct reconnaissance or exploit a sudden gap in the enemy defences. This also allowed the often out-gunned German tanks to lure enemy forces onto their anti-tank defences, rather than try to take them head on.

France, 1940: German infantry on the march. While panzers exploit gaps in the Allied lines,  German foot soldiers infantry rush to secure terrain.

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Although the German lacked heavy tanks with the firepower and armour to match the formidable French Char B1 tanks, they retained an advantage in other areas. They tended to have a crew of five in each of their Panzers which resulted in a more efficient – and therefore quicker - division of labour which could prove to be vital in the middle of a battle.

Luftwaffe support

The Luftwaffe was a sizeable, well-trained, and well-equipped arm of the Wehrmacht, with a number of its members having seen action in the Spanish Civil War. Army Group B was allocated almost 2000 combat aircraft to support its invasion of France, along with over 500 transport and glider aircraft. Over 3000 combat aircraft were allocated to support Army Groups A and C. In total, it was almost double the size of the Allied air force it would face.

It was to mainly provide close support to the land forces with dive-bombers such as the Ju87 Stuka (which effectively acted as flying artillery) and medium bombers such as the Dornier Do17 or Heinkel He111. However, it was flexible enough to carry out operational, tactical, and strategic bombing as required.

A Luftwaffe Heinkel He III medium bomber.

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Order of battle

The German order of battle for Fall Gelb was as follows: The German Army Group A – commanded by Generaloberst (colonel general) Gerd von Rundstedt – would be the main focus of the invasion, advancing through the supposedly impassable Ardennes region. Once across the Meuse River near Sedan, it would pivot north-west and advance on Amiens. At the same time, Army Group B – led by Generaloberst Fedor von Bock – would execute a feint attack to the North hoping to tempt Allied armies to advance into Belgium to confront them. Army Group C – led by Generaloberst Wilhelm Ritter von Leeb – was placed in reserve facing the Maginot Line.

Allied plans

Most of the Allied forces were gathered close to the Belgian border as it was expected that the main German thrust would attempt to bypass the Maginot line and come via Belgium. The Germans invading Belgium would give the French the excuse to advance their own forces into the country to meet them.

If the French forces were unable to reach the Belgium-German border quickly enough, then three additional defence lines had been allocated further back:

• Albert Canal Line (Furthest East: Antwerp – Eban-Emael – Gembloux – Givet)
• Dyle Plan (A long the Dyle River from Antwerp and ending at near Sedan)
• Escaut Plan/Plan E (A longer, curving line from Antwerp stretching to the west close to Lille and Maubeuge before also ending near Sedan)

The three potential Allied defensive positions in Belgium against a German invasion.

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Initially the least ambitious Escaut Plan/Plan E was favoured by the French but by late 1939, as Belgium strengthened its defences and increased the readiness of its army, the Dyle Plan became the favourite.

The 1^st Army Group was tasked with defending the region of France from the Channel Coast to the Maginot Line. It consisted of:

• The French Seventh Army, commanded by Général d'armée Henri Giraud.
• The British Expeditionary Force (BEF) First Army, commanded by Lord Gort.
• The French First Army, commanded by Général d'armée Georges Maurice Jean Blanchard.
• The French Ninth Army, commanded by Général d'armée André Corap.

If the Germans attacked, its role was to advance to the Dale line, with the Seventh Army covering west of Antwerp, ready to move into Holland. The BEF were to defend the stretch of the Dyle from Louvain to Wavre, covering a stretch of about 20 km with nine divisions. To its right, the French First Army of ten divisions would cover the 35km stretch from Wavre across the Gembloux Gap to Namur. The French Ninth Army would place itself south of Namur, close to the Meuse river and the left flank of the French Second Army. The Belgians were expected to delay the German advance sufficiently to give the French and British forces time to get into position.

The battle

On the 10^{th of} May 1940, Five Panzer divisions of Panzergruppe von Kleist began its advance through the Ardennes region. The German XIX Panzer Corps pushed south towards Sedan and the French Second Army while the German XLI Panzer Corps advanced north towards Monthermé and the French ninth article. In order to guard against a swift Allied counter move from the north, the German XV Corps headed towards Dinant.

The Germans execute Erich Von Manstein's plan for Fall Gelb. The Ardennes is just at the east of the red shading which marks the extent of the German advance between 10 - 16 May 1940. 

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The following day, XIX Panzer Corps forced back two cavalry divisions from the Second Army with two other cavalry divisions being withdrawn by the Ninth Army the next day – the Allied commanders needed them to reinforce the defences on the Meuse River. The Germans weren’t far behind, their advance parties arriving in the afternoon although no attempt was made by the Germans to cross the river at this point.

Tiny Luxembourg was the first victim of the German assault though, surrendering after one days fighting, its few hundred strong military no match for the Nazi juggernaut.

The Allies attempted to destroy bridges at Maastricht to hamper any German attempts to cross, it by sending in bombers, but the Allies air component in the area – the 135 Advanced Air Striking Force (AASF) – suffered heavy losses and were reduced to a total of 72 operational aircraft after only two days operations.

French troops and H35 tanks advancing through a damaged village during the invasion of France, 25 May 1940.

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The Netherlands surrendered on the 14 May – the vicious bombing of Rotterdam proving a devastating blow to Dutch morale and the threat of further air attacks persuading the Dutch commanders to throw in the towel.

Sensing an opportunity, the outstanding German panzer general, Heinz Guderian chose to ignore his orders and press on to the English Channel. After capturing Abbeville, and Amiens they clashed with Allied forces at the Battle of Boulogne and the Siege of Calais. Here the advantages of the modern, Blitzkrieg method of attack employed by the Germans were clearly paying dividends as the speed and precision of their advances left the Allies constantly on the back foot, seemingly always having to react to a German manoeuvre rather than being able to take the initiative themselves.

Soldiers from the SS-VT-Division (SS-Verfugungs-Division) during the Invasion of France, The Regiment was formed from the Pre-war cadre of the SS-Verfugungstruppe, which was the first SS combat formation outside of the LSSAH, Hitler's personal guard.

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One exception to this though was the brief but effective Allied counterattack at Arras which temporarily halted the German advance and briefly spread consternation and alarm amongst the German commanders. Ultimately though, it would peter out and the initiative would soon switch back to the Germans again.

The Manstein Plan had been a brilliant success. The British and French forces were split and in disarray with those in the North facing encirclement both the marauding German army Groups A and B – a factor which would shortly lead to the collapse of the Belgian Army.

Furthermore, poor and indecisive leadership amongst the Allies had hampered them at every turn, their commander's apparent paralysis at the unfolding events, preventing any realistic chance of the Allies being able to turn the tide of the battle.

A woman, fleeing from her home with the few possessions she can carry, takes cover behind a tree by the roadside, somewhere in France, on May 18, 1940, during an aerial attack by Nazi planes. Her bicycle, with her belongings tied to it, rests against the tree, to which she clings for protection.

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The British BEF were forced back to the Dunkirk area as the German forces pressed around them. However, thanks to the heroic diversionary battle at Calais, the ‘halt’ order issued to the German panzer forces and the daring implementation of Operation Dynamo, most of the BEF and a significant number of French troops, were successfully evacuated back to Britain – although most of their heavy equipment was left behind.

The Germans now found themselves in a dominant position, controlling the Netherlands, Luxembourg, Belgium and a large chunk of France and with the BEF no longer in the fight. Next they would turn to the remaining French division further south with the launch of Fall Rot.