Battle of France

In World War II, the Battle of France, also known as the Fall of France, was the German invasion of France and the Low Countries, executed from 10 May 1940, which ended the Phony War. The battle consisted of two main operations. In the first, Fall Gelb, German armoured units pushed through the Ardennes, to cut off and surround the Allied units that had advanced into Belgium. The British Expeditionary Force (BEF) and many French soldiers were however evacuated from Dunkirk in Operation Dynamo. In the second operation, Fall Rot, executed from 5 June, German troops outflanked the Maginot Line to attack the larger territory of France itself. Italy declared war on France on 10 June. The French government fled to Bordeaux and Paris was occupied on 14 June. After the French Second Army Group was forced to surrender on 22 June, France capitulated on 25 June. For the Axis, the campaign was a spectacular victory.

France was divided into a German occupation zone in the north and west, a small Italian occupation zone in the southeast and a collaborationist rump state in the south, Vichy France. France and the Low Countries remained under German occupation until after the Allies defeated the German forces in France following the Allied landings in Normandy in 1944.

Prelude
Following the Invasion of Poland of September 1939 that started the Second World War, a period of inaction called the Phony War occurred between the major powers. Hitler had hoped that France and the United Kingdom would acquiesce in his conquest and quickly make peace. This was essential to him as Germany's stock of raw materials — and of the foreign currencies to buy them — was critically low. He was now dependent on supplies from his new ally the Soviet Union, a situation he was uncomfortable with for ideologic reasons. On 6 October he made a peace offer to both Western Powers. Even before these had time to respond to it, he also however formulated on 9 October a new military policy in case their reply would be negative: the Führer-Anweisung N°6, or "Führer-Directive Number 6".

German Strategy
Hitler had always fostered dreams about major military campaigns, to defeat the Western European nations as a preliminary step to the conquest of territory in the East, thus avoiding a two-front war. These intentions were however completely absent from the Führer-Directive N°6. This plan was firmly based on the seemingly more realistic assumption that Germany's military strength would still have to be built up for a number of years and that for the moment only limited objectives could be envisaged, aimed at improving Germany's position to survive a long protracted war[1] in the West. Hitler ordered a conquest of the Low Countries: the Netherlands, Belgium and Luxembourg, to be executed on the shortest possible notice. It should prevent France from occupying them first, which would threaten the vital German Ruhr Area; it also should provide a basis for a successful long-term air and sea campaign against England. There was no mention whatsoever of a possible immediately consecutive attack to conquer the whole of France itself, although as much as possible of the border areas in northern France should be occupied.

While writing the directive Hitler had assumed that such an attack could be initiated within a period of at most a few weeks, but the very day he issued it he was disabused of this illusion. It transpired that he had been misinformed about the true state of Germany's forces. The motorised units had to recover for an estimated three months, repairing the damage to their vehicles incurred in the Polish campaign; the ammunition stocks were largely depleted.

On 10 October the British refused Hitler's offer for peace; on 12 October the French did the same. On 19 October Franz Halder, chief of staff of the OKH, the Army High Command, presented the first plan for Fall Gelb ("Case Yellow"), the pre-war codename of plans for campaigns in the Low Countries: the Aufmarschanweisung N°1, Fall Gelb, or "Instruction for the advance Number 1, Case Yellow". Halder's plan has often been compared to the First World War Von Schlieffen Plan, executed in 1914. It was similar to it in that both plans entailed an advance through the middle of Belgium. But whereas the Von Schlieffen plan had had a surprising gigantic encirclement of the French army in mind, aimed at a decisive victory, Aufmarschanweisung N°1 was based on an unimaginative frontal attack, sacrificing a projected half a million German soldiers to attain the limited goal of throwing the Allies back to the Somme. Germany's strength would then for 1940 be spent; only in 1942[3] the main attack against France could begin.

Hitler was very disappointed by Halder's plan. He had supposed the conquest of the Low Countries could be quick and cheap; but as it was now presented, it would be anything but. It has even been suggested that Halder, who was at the time conspiring against Hitler and had begun carrying a revolver to shoot him in person if necessary, proposed the most pessimistic plan possible to discourage Hitler from the attack entirely.[4] Hitler reacted in fact in two ways. Firstly he decided that the German army should attack early, ready or not, in the hope that Allied unpreparedness might bring about an easy victory after all. He set the date on 12 November. This led to an endless series of postponements, as time and again commanders managed to convince Hitler that the attack should be further delayed for a few days or weeks to remedy some critical defect in the preparations, or to wait for better weather conditions. Secondly, because the plan as it was didn't appeal to him, he tried to make it different, without clearly understanding in which way it could be improved. This mainly resulted in a dispersion of effort, as besides the main axis in central Belgium, secondary attacks were forseen further south. On 29 October Halder let a second operational plan reflect these changes, Aufmarschanweisung N°2, Fall Gelb, which featured a secondary attack on the Liège-Namur axis.

Halder's plan was not only disliked by Hitler. Gerd von Rundstedt, the commander of Army Group A, also disagreed with it. Unlike Hitler however, Von Rundstedt, as a professional soldier, understood perfectly how it should be rectified. Its fundamental and obvious flaw was that it didn't conform to the classic principles of the Bewegungskrieg, the "manoeuvre warfare", that had since the 19th century been the basis of German tactics. A breakthrough would have to be accomplished that would result in the encirclement and destruction of the main body of Allied forces. The logical place to achieve this would be the Sedan axis, which just happened to lie in the sector of Von Rundstedt's Army Group A. Von Rundstedt on 21 October agreed with his chief of staff, Lieutenant-General Erich von Manstein, that an alternative operational plan had to be arranged that would reflect these basic ideas, making his Army Group A as strong as possible at the expense of Army Group B to the north.

While Von Manstein was formulating the new plans in Koblenz, it so happened that Lieutenant-General Heinz Guderian, the commander of the XIXth Army Corps, Germany's elite armoured unit, was lodged in a hotel nearby.[5]. Von Manstein now considered that, if he should involve Guderian in his planning, the tank general might well come up with some rôle for his Army Corps to play in it; and this might then be used as a decisive argument to relocate XIXth Army Corps from Army Group B to Army Group A, much to the delight of Von Rundstedt. At this moment Von Manstein's plan consisted in a move from Sedan to the north, right in the rear of the main Allied forces, to engage them directly from the south in full battle. When during informal discussions invited to contribute to the plan, Guderian proposed a radical and novel idea: not only his army corps, but the entire Panzerwaffe should be concentrated at Sedan. And this concentration of armour should not move to the north but to the west, to execute a swift deep strategic penetration towards the English Channel independently, without waiting for the main body of infantry divisions. This could lead to a strategic collapse of the enemy, avoiding the relatively high number of casualties normally caused by a classic Kesselschlacht or "annihilation battle". Such a risky independent strategic use of armour had been widely discussed in Germany before the war, but had not at all been accepted as received doctrine; the large number of officers serving in the Infantry, which was the dominant Arm of Service, had successfully prevented this. Von Manstein himself had to admit that in this special case however it might be just the thing needed. His main objection was that it would create an open flank of over 300 kilometres, vulnerable to French counterattacks. Guderian convinced him these could be prevented by launching simultaneous spoiling attacks to the south by small armoured units. This however would be a departure from the basic concept of the Führer-Directive N°6.

Von Manstein wrote his first memorandum outlining the alternative plan on 31 October. In it he carefully avoided mentioning Guderian's name and downplayed the strategic part of the armour units, in order not to generate unnecessary resistance. On 6 November, 21 November, 30 November, 6 December, 18 December 1939 and 12 January 1940 a further six memoranda followed, slowly growing more radical in outline. All were rejected by the OKH, nothing of their content reached Hitler.

The crash in Belgium of a light plane, on 10 January 1940, carrying two German officers with a copy of the then-current version of Aufmarschanweisung N°2 forced Hitler to again postpone the invasion. It has often been suggested this incident was the cause of a drastic change in German plans, but this is incorrect; in fact a reformulation of them later on 30 January, Aufmarschanweisung N°3, Fall Gelb, basically conformed to the earlier versions.[7] Late January the troublesome Von Manstein was by instigation of Halder removed to the east by having him on 27 January promoted commander of an army corps in Prussia, to begin his command in Stettin on 9 February. His indignant staff then brought his case directly to the attention of Hitler, who was informed of it on 2 February. Von Manstein was invited to explain his proposal to the Führer personally in Berlin on 17 February; much impressed by it, Hitler the next day ordered the plans to be changed in accordance with Von Manstein's ideas. They mainly appealed to Hitler because they at last offered some real hope of a cheap victory.

The man who had to carry out the change was again Franz Halder — Von Manstein would not be further involved. Halderconsented to shifting the main effort, the Schwerpunkt, to the south. Von Manstein's plan had the virtue of being unlikely (from a defensive point of view) as the Ardennes were heavily wooded and because of their poor road network implausible as a route for an invasion. An element of surprise would therefore be present. It would be essential that the Allies respond as envisioned in the original plans; namely, that the main body of French and British elite troops be drawn north to defend Belgium. To help to ensure this condition, German Army Group B had to execute a holding attack in Belgium and the Netherlands, giving the impression of being the main German effort, in order to draw Allied forces eastward into the developing encirclement and hold them there. To accomplish this, three of the ten available armoured divisions were still allocated to Army Group B.

However Halder had no intention of deviating from established doctrine by allowing an independent strategic penetration by the seven armoured divisions of Army Group A.[8] Much to the outrage of Guderian this element was at first completely removed from the new plan, Aufmarschanweisung N°4, Fall Gelb, issued on 24 February. The crossings of the river Meuse at Sedan should be forced by infantry divisions on the eighth day of the invasion. Only after much debate was this changed in this respect that the motorised infantry regiments of the armoured divisions would establish bridgeheads on the fourth day, to gain four days. Even now the breakout and drive to the Channel would start only on the ninth day, after a delay of five days during which a sufficient number of infantry divisions had to be built up in order to advance together with the armoured units in a coherent mass.

Even when adapted to more conventional methods, the new strategy provoked a storm of protest from the majority of German generals. They thought it utterly irresponsible to create a concentration of forces in a position where they couldn't possibly be sufficiently supplied, while such inadequate supply routes as there were, could easily be cut off by the French. If the Allies didn't react as expected the German offensive could end in catastrophe.[9] Their objections were ignored however; Halder argued that, as Germany's strategic position seemed hopeless anyway, even the slightest chance of a decisive victory outweighed the certainty of ultimate defeat implied by inaction.[10] The adaptation also implied that it would be easier for the Allied forces to escape to the south. Halder pointed out however that if so, Germany's victory would be even cheaper, while it would be an enormous blow to the reputation of the Entente — as the Anglo-French alliance was still commonly known in 1940 — to have abandoned the Low Countries. Moreover Germany's fighting power would then still be intact, so that it might be considered to immediately afterwards execute Fall Rot, the attack on France itself. However a decision to this effect would have to be postponed until after a possible successful completion of Fall Gelb. Indeed German detailed operational planning only covered the first nine days; there was no fixed timetable established for the advance to The Channel. In accordance with the tradition of the Auftragstaktik, much would be left to the judgment and initiative of the field commanders. This indetermination would have an enormous effect on the actual course of events.

In April 1940, the Germans launched for strategic reasons Operation Weserübung, an attack on the neutral countries of Denmark and Norway. The British, French, and Free Poles responded with an Allied campaign in Norway in support of the Norweigans.

Allied Strategy
In September 1939 Belgium and the Netherlands were still neutral. They tried to stay out of the war for as long as possible by adhering to a policy of strict neutrality. Though they in secret made arrangements with the Entente for future cooperation, should the Germans invade their territory, they refused to openly prepare for this. The Supreme Commander of the French army, Maurice Gamelin, suggested in September to take advantage of the fact that Germany was tied up in Poland by occupying the Low Countries before Germany could. This suggestion was not taken up by the French government however.

In September 1939, in a purely political move, French soldiers penetrated 3 miles into the Saar before withdrawing. At this time, France had deployed 98 divisions and 2,500 tanks against German forces consisting of 43 divisions and no tanks. It is probable that the French military would have defeated these forces if the Western allies had had the political will to take up an offensive.

After October, though important parts of the French army in the 1930s had been designed to wage offensive warfare, it was decided not to take the initiative in 1940. The Allies believed that even without an Eastern Front the German government might be destabilised by a blockade, as it had been in the First World War. For the event the Nazi regime wouldn't collapse, a possibility that seemed to grow ever more likely,[11] during 1940 a vast modernisation and enlargement programme for the Allied forces would be implemented, exploiting the existing advantages over Germany in war production to build up an overwhelming mechanised force, including about two dozen armoured divisions, to execute a decisive offensive in the summer of 1941. Should the Low Countries by that date still not have committed themselves to the Allied cause, the Entente firmly intended to violate their neutrality if necessary.[12]

Obviously the Germans might strike first and a strategy would have to be prepared for this eventuality. Neither the French nor the British had anticipated such a rapid defeat in Poland, and the quick German victory was disturbing. Most French generals favoured a very cautious approach. They thought it wise not presume the German intentions could be correctly predicted. A large force should be held in reserve in a central position, north of Paris, to be prepared for any contingency. Should the Germans indeed take the obvious route of advance through Flanders, they should only be engaged in northern France, when their infantry would be exhausted and they had ran out of supplies. When however they would try an attack on the centre of the Allied front, this Allied reserve would be ideally positioned to block it. If the Germans advanced through Switzerland, a large reserve would be the only means to deal with such a surprise.

Gamelin rejected this line of thought. For this he had several reasons. The first was that it was politically unthinkable to abandon the Low Countries to their fate, however prudent it might be from an operational point of view. Certainly the British government insisted that the Flemish coast remain under Allied control. The second reason was that the 1941 offensive had no chance of being decisive if it had to be launched from the north of France against German forces entrenched in central Belgium. The German offensive had to be contained as far east as possible. The last and for him personally most cogent argument was that Gamelin did not consider the French army capable of winning a mobile encounter battle with the German army. The French infantry divisions as yet were insufficiently motorised. The events in Poland only confirmed him in his opinion. Such a confrontation had to be avoided at all cost and Gamelin intended to send the best units of the French army along with the British Expeditionary Force north to halt the Germans at the KW-line, a defensive line that followed the river Dyle, east of Brussels, in a coherent tightly packed continuous front uniting the British, Belgian, and French armies. This plan thus presumed that the Germans planned to concentrate their forces where they could be well supplied by the better road network of northern Belgium.

Gamelin however did not have the personal influence to simply impose his will. The first step he took was to propose the "Escaut" variant as an option for Plan D — the codename for an advance into the Low Countries. It was named after the river in Flanders. This was a shrewd move: protecting the Flemish coast seemed the least one could do; on the other hand it created an enormous salient, showing that it made more sense to defend along the shorter Dyle line, which was precisely the content of Gamelin's next proposal. This however was too transparent. His second "Dyle Plan" met with strong opposition, not growing any less when the 10 January crash confirmed that the German plans conformed to Gamelin's expectations. Also Lord Gort, the commander of the British Expeditionary Force, was beginning to expect that whatever the Germans came up with instead would not be what he had initially predicted. The main objection was that the manoeuvre was very risky. The Allied forces had to complete their advance and entrenchment before the Germans reached the line, for which there seemed to be too little time. When entrenched they would have trouble reacting to German strategic surprises, also because their fuel supplies would have to be replenished. The next problem was that this line was very vulnerable to the German main strength, their large tactical bomber force. Nothing seemed to prevent them from breaking the line by a massive bombardment, forcing the French Army to an encounter battle after all.

Gamelin successfully countered these arguments by adopting the seemingly reasonable assumption that the Germans would try to attempt a breakthrough by concentrating their mechanised forces. They could hardly hope to break the Maginot Line on his right flank or to overcome the allied concentration of forces on the left flank. That only left the centre. But most of the centre was covered by the river Meuse. Tanks were useless in defeating fortified river positions. However at Namur the river made a sharp turn to the east, creating a gap between itself and the river Dyle. This Gembloux Gap, ideal for mechanised warfare, was a very dangerous weak spot. Gamelin decided to concentrate half of his armoured reserves there. By thus assuming that the decisive moment in the campaign would take the form of a gigantic tank battle, he avoided the problem of the German tactical bomber force as air attacks were considered less effective against mobile armoured units, the tanks of which would be hard to hit. Of course the Germans might try to overcome the Meuse position by using infantry. But that could only be achieved by massive artillery support, the gradual build-up of which would give Gamelin ample warning to reinforce.

During the first months of 1940 the size and readiness of the French army steadily grew and Gamelin began to feel confident enough to propose a somewhat more ambitious strategy. He had no intention of frontally attacking the German fortification zone, the Westwall, in 1941, planning instead to outflank it from the north, just as four years later Bernard Montgomery intended in Operation Market Garden. To achieve this, it would be most convenient if he already had an foothold on the north bank of the Rhine, so he changed his plans to the effect that a French army should maintain a connection north of Antwerp with the Dutch National Redoubt, "Fortress Holland". He assigned his sole strategic reserve, the elite 7th Army, to this task. His only reserves now consisted of individual divisions. Again there was much opposition to this "Dyle-Breda-Plan" within the French army, but Gamelin was strongly supported by the British government, because Holland proper was an ideal base for a German air campaign against England.

Germany
Germany deployed about three million men for the battle. Because between 1919 and 1935 no conscription had been allowed by the Treaty of Versailles, in May 1940 only 79 divisions out of a total of 157 raised had completed their training; another fourteen were nevertheless directly committed to battle, mainly in Army Group C and against the Netherlands. Beside this total of 93 front divisions (ten armoured, six motorised) there were also 39 OKH reserve divisions in the West, about a third of which would not be committed to battle. About a quarter of the combat troops consisted of veterans from the First World War, older than forty.

The German forces in the West would in May and June deploy some 2700 tanks and self-propelled guns, including materièl reserves committed; about 7500 artillery pieces were available with an ammunition stock for six weeks of fighting; an organic strength of about 2500 combat aircraft was ready for action, another thousand would during the campaign be committed to battle.

The German Army was divided into three army groups:


 * Army Group A commanded by Gerd von Rundstedt, composed of 45½ divisions including seven armoured, was to execute the decisive movement, cutting a "Sichelschnitt" — not the official name of the operation but the translation in German of a phrase after the events coined by Winston Churchill as "Sickle Cut" (and even earlier "armoured scythe stroke") — through the Allied defenses in the Ardennes. It consisted of three armies: the Fourth, Twelfth and Sixteenth. It had three Panzer corps; one had been allocated to Fourth Army, but the other two were united on a special independent operational level in Panzergruppe Kleist. This was done to better coordinate the approach march to the Meuse river; once bridgeheads had been established they had again to be divided among Twelfth and Sixteenth Army and Panzergruppe Kleist abolished.
 * Army Group B under Fedor von Bock, composed of 29½ divisions including three armoured, was tasked with advancing through the Low Countries and luring the northern units of the Allied armies into a pocket. It consisted of the Eighteenth and Sixth Army.
 * Army Group C, composed of 19 divisions under Wilhelm von Leeb, was charged with preventing a flanking movement from the east, and with launching small holding attacks against the Maginot Line and the upper Rhine. It consisted of the First and Seventh Army.

Allies
Due to a low birthrate that had even further declined during the First World War, France had a severe relative manpower shortage. Its population was furthermore only half of that of Germany. To compensate France had mobilised about a third of the male population between the ages of 20 and 45, bringing the strength of its armed forces to over six million men, more than the entire German Wehrmacht of 5.4 million. Only 2.2 million of these served in army units in the North though, but the total was brought to over 3.3 million by the British, Belgian and Dutch forces in that area. On 10 May there were 93 French, 22 Belgian, ten British and nine Dutch divisions in the North, for a total of 134. Six of these were armoured divisions, 24 motorised divisions. Twenty-two more were being trained or assembled on an emergency basis during the campaign (not counting the reconstituted units), among which two Polish and one Czech division. Beside full divisions the Allies had many independent smaller infantry units: the Dutch had the equivalent of about eight divisions in independent brigades and battalions; the French had 29 independent Fortress Infantry Regiments. Of the French divisions eighteen were manned by colonial volunteer troops; nineteen consisted of "B-divisions", once fully trained units that however had a large number of men over thirty and needed retraining after mobilisation. The best trained Allied forces were the British divisions, fully motorised and having a large percentage of professional soldiers; the worst the very poorly equipped Dutch troops.

The Allied forces deployed an organic strength of about 3100 modern tanks and self-propelled guns on 10 May, another 1200 would be committed to battle in new units or from the materièl reserves; also 1500 obsolete FT-17 tanks were sent to the front for a total of about 5800. They had about 14,000 pieces of artillery. Enjoying thus a clear numerical superiority on the ground,[15] the Allies suffered from an inferiority in the air as only about 1500 combat aircraft were ready for action on the continent. Another 800 had been allocated to combat units. Most of the RAF was kept behind in Britain to defend it against possible German air attacks, but some 750 British planes would reinforce the 400 operational in France, either from the materièl reserves or by flying missions over the continent from British airbases. An additional 2000 aircraft were nominally part of French metropolitan combat aircraft strength but most were of an obsolete type or newly produced planes not yet ready for combat.

The French forces in the north had three Army Groups: the Second and the Third defended the Maginot Line in the east; the First Army Group under Gaston-Henri Billotte was situated in the west and had to execute a swing movement into the Low Countries. At the coast was the 7th Army, reinforced by a Cavalry armoured division, that had to move to the Netherlands via Antwerp; then came nine divisions of the BEF that had to position itself to the right of the Belgian army in the Dyle Line; next was the 1st Army that had to hold the Gembloux Gap, reinforced by two Cavalry armoured divisions and having an Infantry armoured division in reserve. The most southern to move was the 9th Army that had to cover the entire Meuse sector between Namur and Sedan. At Sedan the 2nd Army would form the "hinge" and remain entrenched.

The First Army Group had 35 French divisions; the total of forty divisions of the other Allies in its sector brought their forces equal in number to the combined German forces of Army Group A and B. However, the former only had to confront the eighteen divisions of 9th and 2nd Army and thus would have a large local superiority. To reinforce a threatened sector Gamelin had sixteen strategic reserve divisions available on General Headquarters level, two of them armoured. These were "reserve" divisions in the operational sense only, in fact consisting of high quality troops — most of them had been active divisions in peace time — and thus not comparable to the German reserve divisions that were half-trained. Confusingly, all mobilised French divisions were officially classified as A or B "reserve divisions", although most of them served directly in the front armies.

The North
Germany initiated Fall Gelb on the evening prior to and the night of 10 May. During the late evening of the 9th German forces occupied Luxembourg.[16]. In the night Army Group B launched its feint offensive into the Netherlands and Belgium. Fallschirmjäger (paratroopers) from the 7th Flieger and 22. Luftlande Infanterie-Division under Kurt Student executed that morning surprise landings at The Hague, on the road to Rotterdam and against the Belgian Fort Eben-Emael in order to facilitate Army Group B's advance.

The French command reacted immediately, sending 1st Army Group north in accordance with Plan D. This move committed their best forces, diminished their fighting power through loss of readiness and their mobility through loss of fuel. That evening 7th Army crossed the Dutch border, finding the Dutch already in full retreat. The French and British air command was less effective than their generals had anticipated, and the Luftwaffe quickly obtained air superiority, depriving the Allies of key reconnaissance abilities and disrupting Allied communication and coordination.

The Netherlands
German 18th Army secured all the strategically vital bridges in and toward Rotterdam, which penetrated Fortress Holland and bypassed the New Water Line from the south. However an operation organised separately by the Luftwaffe to seize the Dutch seat of government, The Hague, ended in complete failure. The airfields surrounding the city (Ypenburg, Ockenburg, and Valkenburg) were taken with heavy casualties, only to be lost that same day to counterattacks by the two Dutch reserve infantry divisions. The Dutch would capture or kill 1,745 Fallschirmjäger, shipping 1,200 prisoners to England.

The French 7th Army failed to block German armoured reinforcements of the 9th Panzer Division; they reached Rotterdam on 13 May. That same day in the east the Dutch retreated from the Grebbe Line to the New Water Line, when a counter-offensive to contain a German breach had failed. The Dutch Army, still largely intact, surrendered in the evening of 14 May after the Germans bombed Rotterdam. It considered its strategic situation to have become hopeless and feared a further destruction of the major Dutch cities. However the Dutch troops in Zealand and the colonies continued the fight while Queen Wilhelmina established a government-in-exile in Britain.

Central Belgium
Because Army Group B had been so weakened compared to the earlier plans, the German feint offensive by 6th Army was in danger of stalling immediately, as the Belgian defences on the Albert Canal position were very strong. The main approach route was blocked by Fort Eben-Emael, a large fortress then generally considered the most modern in the world, controlling the junction of the Meuse and the Albert Canal. Any delay might endanger the outcome of the entire campaign, as it was essential that the main body of Allied troops was engaged before Army Group A would establish bridgeheads.

To overcome this difficulty, the Germans resorted to unconventional means. In the early hours of 10 May gliders landed on the roof of Fort Eben-Emael unloading assault teams that disabled the main gun cupolas with hollow charges. The bridges over the canal were seized by German paratroopers. Shocked by a breach in its defences just where they had seemed the strongest, the Belgian Supreme Command withdrew its divisions to the KW-line five days earlier than planned. At that moment however the BEF and the French 1st Army were not yet entrenched. When Erich Hoepner's XVI Panzer Corps, consisting of 3rd and 4th Panzer Divisions was over the bridges launched in the direction of the Gembloux Gap, this seemed to confirm the expectations of the French Supreme Command that here would be the German Schwerpunkt. The two French Cavalry armoured divisions, the 2nd DLM and 3rd DLMs (Division Légère Mécanique, "Mechanised Light Division") were ordered forward to meet the German armour and cover the entrenchment of 1st Army. The resulting Battle of Hannut on 12 and 13 May was, with about 1500 AFVs participating, the largest tank battle until that date. The French lost about a hundred tanks, the Germans lost over 160 but managed on the second day to breach the screen of French tanks, which on 14 May however were successfully withdrawn after having gained enough time for the 1st Army to dig in. Hoepner against orders tried on 15 May to break the French line, the only time in the campaign when German armour would frontally attack a strongly held fortified position; the attempt was repelled by the 1st Moroccan Infantry Division, costing 4PD another 120 tanks. This defensive success for the French was however already made irrelevant by the events further south.

The Centre
In the centre, the progress of German Army Group A was to be delayed by Belgian motorised infantry and French Light Divisions of the Cavalry (Divisions Légères de Cavalerie) advancing into the Ardennes. These forces however had an insufficient anti-tank capacity to block the surprisingly large number of German tanks they encountered and quickly gave way, withdrawing behind the Meuse. The German advance was however greatly hampered by the sheer number of troops trying to force their way through the poor road network. The time-tables proved to have been wildly optimistic and soon a traffic congestion formed, in the beginning to the east reaching well over the Rhine, that would last for almost two weeks. This made Army Group A very vulnerable to French air attacks, but these didn't materialise. Although Gamelin was well aware of the situation, the French tactical bomber force was far too weak to challenge German air superiority so close to the German border. However on the 11th Gamelin ordered many reserve divisions to begin reinforcing the Meuse sector. Because of the danger the Luftwaffe posed, movement over the rail network was limited to the night, slowing the reinforcement, but the French felt no sense of urgency as the build-up of German divisions would be accordingly slow.

The German advance forces reached the Meuse line late in the afternoon of 12 May. To allow each of the three armies of Army Group A to cross, three major bridgeheads were to be established: at Sedan in the south, at Monthermé twenty kilometres to the northwest and at Dinant, another fifty kilometres to the north. The first units to arrive had hardly even a local numerical superiority; their already insufficient artillery support was further limited by an average supply of just twelve rounds per piece.

Sedan
At Sedan the Meuse Line consisted of a strong defensive belt, constructed six kilometres deep according to the modern principles of zone defence on slopes overlooking the Meuse valley and strengthened by 103 pillboxes, manned by 147th Fortress Infantry Regiment. The deeper positions were held by the 55th Infantry Division (55e DI), and this was only a grade “B” reserve division, but already reinforcements were arriving; in the morning of 13 May 71st DI was inserted to the east of Sedan, allowing 55th DI to narrow its front by a third and deepen its position to over ten kilometres. Furthermore it had a superiority in artillery to the German units present on 13 May.[18] The French command fully expected that the Germans would only attack such formidable defences when a large infantry and artillery force had been build up, a concentration that apparently could not be completed before 20 May, given the traffic congestion — a date very similar to Halder's original projection. It thus came as a complete surprise when crossing attempts were made as early as the fourth day of the invasion.

On 13 May the German XIX Army Corps forced three crossings near Sedan, executed by the motorised infantry regiments of 1st, 2nd and 10th Panzerdivision, reinforced by the elite Großdeutschland infantry regiment. Instead of slowly massing artillery as the French expected, the Germans concentrated most of their tactical bomber force to punch a hole in a narrow sector of the French lines by carpet bombing (punctuated by dive bombing). Between 12:00 and 16:00 Luftflotte 3, supported by Luftflotte 2, executed the heaviest air bombardment the world had yet witnessed and the most intense by the Luftwaffe in the entire war,[19] carrying out that day 1,215 bomber sorties, mainly against the narrow strip of the Sedan river bend. The forward platoons and pillboxes of the 147 RIF, little affected by the bombardment, held their positions throughout most of the 13th, initially repulsing the crossing attempts of 2nd and 10th Panzerdivision on their left and right; however in the centre of the river bend there was a gap in the line of bunkers. In the late afternoon Großdeutschland penetrated this position, trying to quickly exploit this opportunity. The deep French zone defence had been devised to defeat just this kind of infiltration tactics; it now transpired however that the morale of the deeper company positions of the 55th DI had been broken by the impact of the German air attacks: they had been routed or were too dazed to any longer offer effective resistance. The French supporting artillery batteries had fled and this created an impression among the remaining main defence line troops of the 55e DI that they were isolated and abandoned. They too went into rout by the late evening of 13 May. At a cost of a few hundred casualties[20] the German infantry had penetrated up to eight kilometres into the French defence zone by midnight; even then most of the infantry hadn't crossed yet, much of the success being due to the actions of just six platoons, mainly assault engineers.[21]

The disorder begun at Sedan was spread down the French lines by groups of haggard and retreating soldiers. During the night the second, 295th, regiment of 55th DI, holding the last prepared defence line at the Bulson ridge, ten kilometres from the Meuse, was panicked by the false rumour that German tanks were already behind their positions. It fled, creating a gap in the French defences, before even a single German tank had crossed the river. This "Panic of Bulson" involved the divisional artillery, so that the crossing sites were no longer in reach of the French batteries.

In the morning of 14 May two French FCM 36 tank battalions (4 and 7 BCC) and the reserve regiment of 55th DI, 213rd RI, executed a counterattack on the German bridgehead. It was repulsed at Bulson by the first German armour and anti-tank units which had been rushed across the river from 7:20 A.M. on the first pontoon bridge. That day every available Allied light bomber was employed in an attempt to destroy the three bridges; but, despite heavy losses for the RAF, mostly caused by a concentration of over 300 AA-guns, they failed to hit them.

The commander of XIX Army Corps, Heinz Guderian, on 12 May had indicated that he wanted to enlarge the bridgehead to at least twenty kilometres. His superior Ewald von Kleist however ordered him to limit it to a maximum of eight kilometres before consolidation. On 14 May, 11:45 AM, Von Rundstedt confirmed this order,[22] which basically implied that the tanks should now start to dig in. Nevertheless Guderian immediately disobeyed, expanding the perimeter to the west and to the south.

In the original Von Manstein plan as Guderian had suggested it, secondary attacks would be carried out to the southeast, in the rear of the Maginot Line, to confuse the French command. This element had been removed by Halder. Guderian now sent 10th Panzer Division and Großdeutschland south to execute precisely such a feint attack,[23] using the only available route south over the Stonne plateau. However the commander of the French Second Army, General Charles Huntzinger, intended to carry out at the same spot a counterattack by the armoured 3e Division Cuirassée de Réserve to eliminate the bridgehead. This resulted in an armoured collision, both parties in vain trying to gain ground in furious attacks from 15 to 18 May, the village of Stonne changing hands many times. Huntzinger considered this at least a defensive success and limited his efforts to protecting his flank. However in the evening of 16 May Guderian removed 10 PD from the effort, having found a better destination for this division.

Guderian had turned his other two armoured divisions,1st and 2nd Panzerdivision sharply to the west on 14 May. On 15 May his motorised infantry dispersed in heavy fighting the reinforcements of the newly formed French 6th Army in their assembly area west of Sedan, undercutting the southern flank of the French Ninth Army by 40 km and forcing the 102nd Fortress Division to leave its positions that had blocked the tanks of XVI Army Corps at Monthermé. While the French Second Army had been seriously mauled and had rendered itself impotent, now Ninth Army began to disintegrate completely, for in Belgium also its divisions, not having had the time to fortify, had been pushed back from the river by the unrelenting pressure of German infantry, allowing the impetuous Erwin Rommel to break free with his 7th Panzer Division. A French armoured division (1st DCR) was sent to block him but, advancing unexpectedly fast, he surprised it while refueling on 15 May and dispersed it, despite some losses caused by the heavy French tanks.

Blitzkrieg
The Battle of France is often hailed as the first historical instance of the Blitzkrieg tactic. Blitzkrieg can be defined as defeating the enemy by means of a strategic envelopment executed by mechanized forces leading to operational collapse. Von Manstein certainly had had a strategic envelopment in mind. However the three dozen infantry divisions that followed the Panzer Corps were not there merely to consolidate their gains. It was to be the other way around. In the eyes of the German High Command the Panzer Corps now had fulfilled a precisely circumscribed task. Their motorized infantry component had secured the river crossings, their tank regiments had conquered a dominant position. Now they had to consolidate, allowing the infantry divisions to position themselves for the real battle: perhaps a classic Kesselschlacht when the enemy should stay in the north, perhaps an encounter fight when he should try to escape to the south. In both cases an enormous mass of German divisions, both armoured and infantry, would cooperate to annihilate the enemy, in accordance with established doctrine. The Panzer Corps were not to bring about the collapse of the enemy by themselves alone. They should halt.

On 16 May, however, both Guderian and Rommel disobeyed their explicit direct orders in an act of open insubordination against their superiors and moved their divisions many kilometers to the west, as fast as they could push them. Guderian reached Marle, 80 kilometers from Sedan; Rommel crossed the river Sambre at Le Cateau, a hundred kilometers from his bridgehead, Dinant. While nobody knew the whereabouts of Rommel (he had advanced so quickly that he was out of range for radio contact, earning his 7th Panzer Division the nickname Gespenster-Division, "Ghost Division"), an enraged von Kleist flew to Guderian on the morning of 17 May and after a heated argument relieved him of all duties. However, von Rundstedt would have none of it and refused to confirm the order.

It has proven difficult to explain the actions of both generals. Rommel was forced to commit suicide by Hitler before the end of the war and thus never could clarify his behavior in full freedom. After the war, Guderian claimed to have acted on his own initiative, essentially inventing Blitzkrieg on the spot. Some historians have since considered this an empty boast, denying any fundamental divide within contemporaneous German operational doctrine, downplaying the conflict as a mere difference of opinion about timing and pointing out that Guderian's claim is inconsistent with his professed role as the prophet of Blitzkrieg even before the war. However his prewar writings in fact explicitly reject strategic envelopment by mechanized forces alone as a generally sufficient means to cause operational collapse. Also, there is no explicit reference to such tactics in the German battle plans.

Allied Reaction
The Panzer Corps now slowed their advance considerably but had put themselves in a very vulnerable position. They were stretched out, exhausted and low on fuel; many tanks had broken down. There now was a dangerous gap between them and the infantry. A determined attack by a fresh large mechanized force could have cut them off and wiped them out.

The French High Command, however, was reeling from the shock of the sudden offensive and was stung by a sense of defeatism. On the morning of 15 May French Prime Minister Paul Reynaud telephoned the new Prime Minister of the United Kingdom Winston Churchill and said "We have been defeated. We are beaten; we have lost the battle." Churchill, attempting to console Reynaud, reminded the Prime Minister of the times the Germans had broken through allied lines in World War I only to be stopped. However, Reynaud was inconsolable.

Churchill flew to Paris on 16 May. He immediately recognized the gravity of the situation when he observed that the French government was already burning its archives and preparing for an evacuation of the capital. In a sombre meeting with the French commanders, Churchill asked General Gamelin, "Ou est la masse de manoeuvre?" ["Where is the strategic reserve?"] which had saved Paris in the First World War. "Aucune" ["There is none,"] Gamelin replied. Later, Churchill described hearing this as the single most shocking moment in his life. Churchill asked Gamelin when and where the general proposed to launch a counterattack against the flanks of the German bulge. Gamelin simply replied "inferiority of numbers, inferiority of equipment, inferiority of methods".[24]

Gamelin was right; most reserve divisions had by now been committed. The only armoured division still in reserve, 2nd DCR, attacked on 16 May. However the French armoured divisions of the Infantry, the Divisions Cuirassées de Réserve, were – despite their name – very specialized breakthrough units, optimized for attacking fortified positions. They could be quite useful for defense, if dug in, but had very limited utility for an encounter fight: they could not execute combined infantry–tank tactics as they simply had no important motorized infantry component; they had poor tactical mobility as the heavy Char B1 bis, their main tank in which half of the French tank budget had been invested, had to refuel twice a day. So 2nd DCR divided itself in a covering screen, the small subunits of which fought bravely – but without having any strategic effect.

Of course, some of the best units in the north had yet seen little fighting. Had they been kept in reserve they could have been used for a decisive counter strike. But now they had lost much fighting power simply by moving to the north; hurrying south again would cost them even more. The most powerful allied division, the 1st DLM (Division Légère Mécanique, "light" in this case meaning "mobile"), deployed near Dunkirk on 10 May, had moved its forward units 220 kilometers to the northeast, beyond the Dutch city of 's-Hertogenbosch, in 32 hours. Finding that the Dutch had already retreated to the north, it had withdrawn and was now moving to the south. When it would reach the Germans again, of its original 80 SOMUA S 35 tanks only three would be operational, mostly as a result of breakdown.

Nevertheless, a radical decision to retreat to the south, avoiding contact, could probably have saved most of the mechanized and motorized divisions, including the BEF. However, that would have meant leaving about thirty infantry divisions to their fate. The loss of Belgium alone would be an enormous political blow. Besides, the Allies were uncertain about German intentions. They threatened in four directions: to the north, to attack the allied main force directly; to the west, to cut it off; to the south, to occupy Paris and even to the east, to move behind the Maginot Line. The French decided to create a new reserve, among which a reconstituted 7th Army, under General Touchon, using every unit they could safely pull out of the Maginot Line to block the way to Paris.

Colonel Charles de Gaulle, in command of France's hastily formed 4th Armored Division, attempted to launch an attack from the south and achieved a measure of success that would later accord him considerable fame and a promotion to Brigadier General. However, de Gaulle's attacks on 17 and 19 May did not significantly alter the overall situation.

To the Channel
While the Allies did little either to threaten them or escape from the danger they posed, the Panzer Corps used 17 and 18 May to refuel, eat, sleep, and get some more tanks in working order. On 18 May Rommel made the French give up Cambrai by merely feinting an armoured attack.

The Allies seemed incapable of coping with events. On May 19, General Ironside, the British Chief of the Imperial General Staff, conferred with Gort, commander of the British Expeditionary Force at his headquarters near Lens. Gort reported that the Commander of the French Northern Army Group, General Billotte, had given him no orders for eight days. Ironside confronted Billotte, whose own headquarters was nearby, and found him apparently incapable of taking decisive action. Even when the powerfully built Ironside shook him by his tunic button, this produced no effect.

Ironside had originally urged Gort to save the BEF by attacking south-west towards Amiens. Gort replied that seven of his nine divisions were already engaged on the Scheldt River, and he had only two with which to mount such an attack. Ironside returned to Britain concerned that the BEF was already doomed.

On the same day, the German High Command grew very confident. They determined that there appeared to be no serious threat to them from the south – indeed General Franz Halder, Chief of Army General Staff, toyed with the idea of attacking Paris immediately to knock France out of the war in one blow. The Allied troops in the North were retreating to the river Escaut, their right flank giving way to the 3rd and 4th Panzer Divisions. It would be foolish to remain inactive any longer, allowing them to reorganize their defense or escape. Now it was time to bring them into even more serious trouble by cutting them off. The next day the Panzer Corps started moving again, smashed through the weak British 18th and 23rd Territorial Divisions, occupied Amiens and secured the westernmost bridge over the river Somme at Abbeville, isolating the British, French, Dutch, and Belgian forces in the north. In the evening of 20 May a reconnaissance unit from 2nd Panzer Division reached Noyelles, a hundred kilometers to the west. There they could see the estuary of the Somme flowing into The Channel.