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On the morning of January 10, 1940, engine failure forced a Messerschmitt Bf-108 Taifun to land in a deserted field just inside the Belgian border. From the downed plane emerged Luftwaffe Majors Erich Hoenmanns, the pilot, and Helmuth Reinberger, who was carrying in his briefcase the highly secret plan of an impending German invasion of neutral Belgium and the Netherlands. Reinberger’s attempt to burn the documents was frustrated by a Belgian border patrol, which quickly arrived on the scene, arrested the two German officers, seized the partially charred papers and handed them over to the Belgian high command.

The capture of the German invasion plan initiated a chain of events that had a profound impact on the course of World War II in Western Europe. During a council of war on January 12, 1940, the French high command concluded that the Reinberger documents were genuine and not a German foil. They drew this conclusion in part because the documents reinforced their belief that the main thrust of the German offensive would come through northern Belgium rather than across the Maginot Line, the 87-mile-long fortified barrier that straddled the Franco-German border from Belgium to Switzerland.

The Reinberger documents also appeared to confirm the supposed wisdom of the Allied war plan approved on November 14, 1939. Code-named ‘Plan Dyle,’ it called for four of the five Anglo-French armies to advance to the line of the Dyle River in Belgium at the outset of the battle to stop the Germans before they could reach French soil.

On the extreme left flank of the Allied armies advancing into Belgium were the seven divisions of General Henri Giraud’s French Seventh Army. It would be accompanied, on its right flank, by the nine divisions of the British Expeditionary Force (BEF), under General John Lord Gort. To the right of the BEF, the French First Army, comprising 10 divisions under General Jean-Georges Maurice Blanchard, would have the responsibility of blocking a likely German attack through the Gembloux Gap, a 30-mile-wide corridor between the Dyle and Meuse rivers.

On the right flank of the First Army, only the left wing of French General André Corap’s Ninth Army (nine divisions in all) would advance into Belgium, marching to a line running along the Meuse River from Namur south to the French frontier. The right wing of Corap’s army would remain fixed on French soil, holding the line of the Meuse, from the French-Belgian border to the town of Sedan. To the right of the Ninth Army, the five divisions of General Charles Huntziger’s French Second Army would also remain stationary in France. It would be responsible for defending the frontier from Sedan to the Maginot Line. These fortifications, plus the Rhine River defenses, would be manned by the Second and Third army groups.

General Alphonse-Joseph Georges, who would command the Allied advance to the Dyle Line, argued vigorously against the plan. He feared that his units would not have time to prepare defensive positions in Belgium before the Germans attacked them. He was even more horrified to learn that General Maurice Gamelin, the French commander in chief and author of the Dyle Plan, had also decided to send Giraud’s Seventh Army — the only available reserve army — into Holland, at least as far as Breda, to forge a link between the Dutch and Belgian defenses.

Georges warned Gamelin that sending the Seventh Army far from the center of the Allied front, which was opposite the Ardennes Forest, was a potentially disastrous move. ‘If…the main enemy attack came in our center,’ a concerned Georges wrote, ‘on our front between the Meuse and the Moselle, we could be deprived of the necessary means to repel it.’But Gamelin did not believe the main German thrust would come through the Ardennes. A German army advancing through the forest, Gamelin was fond of pointing out, would have to use narrow, winding roads that threaded through rugged and heavily wooded hills — all of which were supposedly a defender’s dream landscape.

The French chief of staff, however, overestimated the deterrent value of the Ardennes. The forest was not as thick as he thought it was, and in reality the mountains were nothing more than a series of not-too-steep hills. Moreover, a good road network traversed the Ardennes between Sedan and the German border.

Nevertheless, an Allied advance into Belgium presented advantages that Gamelin was not prepared to abandon and which no doubt caused him to downplay the Ardennes threat. Not only would the move add the 22 divisions of the Belgian army to his combined strength, it would also shorten the Allied front by 35 miles. Moreover, an advance into Belgium would keep the German army away from the northern industrial and mining region of France. It would also keep the Luftwaffe from establishing bases near the English Channel, from which German warplanes could more easily attack Britain. This was a factor that prompted the British to support the Dyle Plan in the first place.

What is mind-boggling, however, is Gamelin’s refusal to keep the Seventh Army in general reserve after he began to receive intelligence reports as early as November 1939 that indicated the Germans had shifted the center of their planned attack farther south. In March 1940, Allied intelligence had located seven German panzer divisions deployed along the Franco-Belgian frontier between Sedan and Namur, the sector defended by the French Ninth Army. Gamelin did nothing to reinforce the Sedan sector even after he received another intelligence report, on the last day of April, warning that the German attack was set for May 8-10 and that Sedan would be at its center. Gamelin simply could not envision abandoning the Dyle Plan.

Hitler, by contrast, was much less rigid when it came to reconsidering his plans. The capture by the Allies of Reinberger’s documents had prompted the enraged Führer to scrap the now compromised German war plan, code-named Fall Gelb (Plan Yellow), and demand that his generals quickly work up an alternative. This new plan would ultimately bring about the defeat of France in six weeks and carry the Nazi warlord to the brink of total victory in the West.

On February 17, 1940, the gist of the revised version of Plan Yellow was described to the Führer by its primary author, Lt. Gen. Erich von Manstein. Manstein insisted that the point of attack for the German armored blitz, which would employ concentrated masses of panzer divisions, mechanized infantry and close-support aircraft, must avoid northern Belgium, where the Allies anticipated it. Instead Manstein believed that the center of the attack must be moved to the weakest point of the French line — that is, near Sedan, on the Meuse River. After breaking through the French defenses, the panzers should speed across northern France to the Channel coast near Abbeville. If the plan worked, the bulk of the Allied armies would be cut off in Belgium. After their destruction, Manstein added, the rest of the French army could be enveloped and destroyed ‘with a powerful right hook.’

Hitler agreed with most of Manstein’s revisions to Plan Yellow. As early as October 1939, he had expressed his first misgivings about the original plan. After listening to army chief of staff General Franz Halder give a presentation on the plan, Hitler said, ‘That is just the old [World War I] Schlieffen Plan, with a strong flank along the Atlantic coast; you won’t get away with an operation like that twice running.’

Hitler had quite a different idea. He suggested a vast encirclement of the enemy, led by panzer divisions thrusting across the Meuse River and then on to the English Channel. This was terrain he had fought on during World War I, and he knew it was ideal for tanks.

But Hitler envisioned only a few divisions participating in the attack through the Ardennes. Manstein, on the other hand, insisted that the spearhead had to be as strong as possible. Therefore, he argued that all of Germany’s 10 existing panzer divisions should be concentrated opposite the Ardennes. Hitler decided to compromise. Seven panzer divisions would be deployed opposite the Ardennes, while three would be stationed farther north, so as not to alert the Allies to the change in the German war plan.

The new version of Plan Yellow was aptly christened Sichelschnitt (Cut of the Sickle). It called for the spearhead of the western offensive to strike the French on the Meuse River between Namur and Sedan, as Manstein desired. The attack on Sedan was assigned to General Heinz Guderian’s XIX Panzer Corps, consisting of the 1st, 2nd and 10th Panzer divisions, assisted by Hitler’s elite Grossdeutschland motorized infantry regiment. These units would be followed and supported by General Gustav von Weiterscheim’s XIV Motorized Infantry Corps and other divisions of General Sigmund von List’s Twelfth Army.

Farther north, the 6th and 8th Panzer divisions of General Georg-Hans Reinhardt’s LI Panzer Corps would head for Monthermé, a small town downstream from Sedan. The 5th and 7th Panzer divisions of General Hermann Hoth’s XV Panzer Corps, a part of General Günther von Kluge’s Fourth Army, would provide flank cover for Reinhardt’s corps by crossing the Meuse farther north, at Dinant.

The five panzer divisions belonging to Guderian and Reinhardt, the spearhead of the attack, were welded together in an integrated armored group under General Ewald von Kleist, a former cavalryman not well disposed to armored warfare, and thus sufficiently cautious to ease Hitler’s fears about the exposed flanks of the panzers as they raced across France. All of these forces were allotted to Army Group A, under the command of General Gerd von Rundstedt, who also would prove to have an excessively cautious attitude toward the new blitzkrieg strategy.

While Rundstedt’s Army Group A was expected to break through the Allied center, General Fedor von Bock’s Army Group B and General Wilhelm von Leeb’s Army Group C would be playing important roles, too. Bock’s two armies, the Eighteenth, under General George von Küchler, and the Sixth, under General Walter von Reichenau, would have to crush resistance in the Netherlands as quickly as possible in order to protect the northern flank of Rundstedt’s army group. They would also have to advance far enough into Belgium to draw the Allies, which would be trying to get into their rear, away from Rundstedt’s Forces.

At the same time, on the southern part of the front, Leeb would have to convince the Allies that Germany was prepared to launch a secondary strike against the Maginot Line, in order to dissuade the French from shifting the divisions manning the fortifications northward to counter Rundstedt’s crossing of the Meuse.

As winter gave way to spring, the Germans were busy taking steps to ensure that the redeployments required by Sichelschnitt were hidden from the Allies. They hoped that General Gamelin would find no reason to change his plan to send the cream of the Allied armies into a carefully planned trap in northeastern Belgium.

During the early morning of May 10, 1940, the most massive mechanized force assembled up to that time began crossing Germany’s border with Belgium and Luxembourg. Panzer Group Kleist — five panzer divisions, with 134,000 soldiers, 41,000 motor vehicles and more than 1,600 tanks and reconnaissance vehicles — spearheaded the German attack. ‘Like a giant phalanx,’ remarked General Günther von Blumentritt, Rundstedt’s chief of operations, the German forces’stretched back for a hundred miles, the rear rank lying fifty miles to the east of the Rhine.’

Kleist’s panzer divisions advanced quickly through the Ardennes, meeting only light resistance from Belgian and French mechanized cavalry units. This they quickly brushed aside, and by the evening of May 12, two of Guderian’s three panzer divisions had reached the Meuse River on either side of Sedan. The next day they planned to cross the river. By then the lead units of Maj. Gen. Erwin Rommel’s 7th Panzer Division had already gotten across the Meuse just below Dinant. While the Germans were pushing through the Ardennes Forest, farther to the north the Allies were advancing into Belgium. By the evening of May 11, all nine divisions of the BEF were in place along the Dyle River. Between the BEF and the city of Namur, some 25 miles to the east, stretched the Brabant Plain, for centuries the avenue of Germanic invasions into the French heartland.

Filling the Gembloux Gap was Blanchard’s First Army — eight infantry divisions, three of them mechanized. Blanchard’s force was regarded as one of the best armies France possessed.

On the extreme left wing of the Allied front, the French Seventh Army spent May 10 advancing into the Netherlands. Giraud was instructed to move as far north as Breda to link up with the Dutch. But by the time his army reached Breda, the Dutch army had already withdrawn to cover Rotterdam. Instead of linking up with his allies, Giraud encountered the advance elements of Lt. Gen. Alfred Ritter von Hubicki’s 9th Panzer Division. The French also were attacked by Luftwaffe aircraft, whose bombs and strafing devastated Giraud’s 25th Infantry Division and scattered the 1st Light Cavalry Division. The next day, Giraud was ordered to withdraw his army from Holland and regroup in Belgium, west of the Escaut River. So ended the French attempt to save the Netherlands. On May 14, the Dutch surrendered.

Giraud’s army was sorely missed on the Meuse River line facing the Ardennes Forest. Had it remained in general reserve, as General Georges had desired, it might have been able to stem the impending German onslaught.

As Guderian’s three panzer divisions prepared to cross the Meuse near Sedan, they faced the weakest army in the French order of battle, General Corap’s Ninth. Of Corap’s seven infantry divisions, only two — the 5th Motorized and 4th North African — were Regular divisions. The others were filled by reservists. Two of the reserve divisions, the 61st and 53rd infantries, were classified as Series B divisions, which meant badly armed, overage and undertrained. The men were led by older-than-average officers, most of whom had been called out of retirement. With the exception of its cavalry corps, which had lost many of its light tanks in the Ardennes, the Ninth Army had no armored units. Still, no one had expected its soldiers to do much fighting. Gamelin had deployed Corap’s army near the Ardennes because he had considered the forest impenetrable and the Meuse River impassable.

The confidence of the French generals was severely jolted, however, as they watched the Germans emerge from the ‘impenetrable’ Ardennes on the afternoon of May 12. There was, recalled X Corps commander General Claude Grandsard, ‘an almost uninterrupted descent of infantry, armored vehicles and motorized infantry.’ What Grandsard witnessed was the advance of Guderian’s 1st and 10th Panzer divisions (the 2nd Panzer still lagged far behind in the Ardennes Forest).

Another French general, Charles Menu, later wrote that if the French artillery had delivered a full-scale, concerted blow at this assemblage, Guderian’s armored formations might have been broken up before they even attempted the Meuse crossing. ‘What a chance,’ Menu observed, ‘for the artillery to strike hammer blows’ and turn those armored units ‘into scraps of burnt and twisted metal.’ But, amazingly, the French artillery did not open up. Grandsard later explained that ‘as a counterattack would have to be launched with as much weight as possible against the Germans massing for the assault, our artillery was very sparing with its ammunition.’

Nor was the French air force called in to strike at the concentrated masses of German tanks. The headquarters of the Second Army told nearby air force units that their bombers were not needed because there was more than enough artillery on hand to deal with the Germans.

Guderian’s crossing of the Meuse was preceded by an intense bombardment that began at 10 a.m. on May 13 and continued for five straight hours. Two hundred Junkers Ju-87B Stuka dive bombers and 310 Dornier Do-17 bombers, escorted by 200 fighters, pounded the French positions. Taking advantage of the smoke that covered the valley, the Germans moved 20mm and 37mm automatic cannons, along with the new 88mm anti-aircraft guns, to the very edge of the river and fired point-blank into the French bunkers and gun emplacement barely 100 yards away.

One by one the French guns were smashed, their crews blinded by splinters or horribly mutilated by shells exploding within their bunkers’ restricted interiors. ‘The gunners stopped firing and went to the ground,’ General Edmond Ruby recalled. ‘Their only concern was to keep their heads well down. They did not dare move. Five hours of this torture was enough to shatter their nerves. They became incapable of reacting to the approaching enemy infantry.’ Many of the defenders fled in panic.

Under the cover of the bombardment’s smoke and explosions, German infantry began crossing the river in rubber rafts at 3:30 p.m. Once across, they rushed the French pillboxes and knocked them out one by one. By 2 the next morning, the Germans had built a pontoon bridge over the river, and tanks poured across it. A French counterattack by two tank battalions at dawn was easily repulsed by the 2nd Panzer Division. By the afternoon of May 14, all three of Guderian’s panzer divisions were across the Meuse and had advanced as far as 10 miles south of the river.

At that point, with the French line shattered, Guderian decided to ignore any possible threat to his southern flank. He boldly ordered his armor to turn west and head for Rethel, a French town on the Aisne River, 32 miles southwest of Sedan. Its capture would complete the rupture of the link between the French Second and Ninth armies. This would open the way to Paris, little more than 100 miles away, or to the English Channel, 50 miles farther west. However, after German intelligence warned Guderian that additional French tanks were moving toward Stonne, a village 10 miles south of Sedan, he decided to keep the 10th Panzer Division behind to defend his southern flank until additional infantry could be brought up.

The next day, May 15, a badly coordinated counterattack by the French 3rd Armored Division was easily repulsed, and the 10th Panzer Division joined its two sister divisions in their westward dash to the sea. By that night, a reconnaissance detachment of Guderian’s 2nd Panzer Division made contact with Reinhardt’s panzers at Montcornet, 40 miles west of Sedan. Only 24 hours earlier the German bridgeheads across the Meuse had been three isolated bulges; now they formed one continuous pocket 62 miles wide. For the Germans the way west lay open, with virtually no obstacles between them and the English Channel.

Panzer Group Kleist continued its dash to the Channel after breaking through the French front on the Meuse. By May 20, elements of Guderian’s panzer corps reached the Channel coast near Abbeville. They then advanced northward along the coast toward Boulogne and Calais. At the same time, Reinhardt’s panzer corps advanced north on the right of, and just behind, Guderian’s corps. It was followed in turn by the two panzer divisions of Hoth’s corps. Then on May 24, just as German tanks were about to move against the thinly defended canal line west of Dunkirk, where much of the BEF waited to be rescued, Hitler ordered an abrupt halt to the advance.

Why Hitler issued that order, when the panzers were closer to Dunkirk than almost all of the French and British troops, is one of the great puzzles of World War II. The rationale behind his decision apparently originated with General Kluge, the commander of the Fourth Army. On May 23, Kluge suggested to Rundstedt that the tanks should ‘halt and close up,’ a move that also would allow the Luftwaffe time to move its bases closer to the panzers’ area of operation.

Kluge’s argument made sense to Rundstedt. The army group commander was also concerned about the heavy losses his armor had suffered in the advance across France. Kleist reported that 50 percent of his tanks were unfit for action (although he did not mention that many of these vehicles could be repaired in a day or two). If the other panzer divisions had suffered comparable losses, Rundstedt feared, they would not be strong enough to carry out Operation Red, the second phase in the conquest of France.

Another factor that prompted Rundstedt to halt the panzers was a message that morning from General Walter von Brauchitsch stating that completing the encirclement of the enemy forces retreating toward Dunkirk would be handed over to Bock’s Army Group B so that Rundstedt could concentrate on preparations for the drive toward Paris. As far as Rundstedt was now concerned, his army group had completed the work it had been assigned in Sichelschnitt: break through the French front and advance to the English Channel. For Rundstedt, British historian Basil Liddell Hart remarked, Dunkirk ‘was now barely in the corner of his eye.’

Hitler, who had the final say in the matter, backed Rundstedt’s halt order. Like Rundstedt, he was worried about the German southern flank. Not wanting victory ripped from his grasp by an Allied counterattack across the Somme River — as victory had been snatched from the German army in the Battle of the Marne during World War I — Hitler wanted all the motorized formations to wait until infantry could be brought up to reinforce the southern flank. Moreover, he felt that the canals and marshy terrain surrounding Dunkirk were not really suitable for armored operations.

As a lance corporal in World War I, Hitler had seen British tanks bogged down by the very same terrain during the Poelcappelle offensive in October 1917. He also agreed with Rundstedt that it was vitally necessary to save the panzers for the next phase of the campaign. In addition, Hitler was apparently convinced by Reichsmarschall Hermann Göring, who wanted a share of the campaign’s glory, that his Luftwaffe could finish off the British.

The tank commanders reacted furiously to the halt order. General Wilhelm Ritter von Thoma recalled that when he received the order, he was riding with his leading tanks near Bergues. From there, he said with some exaggeration, ‘he could almost look into the town of Dunkirk,’ only five miles to the north.

Thoma sent back radio messages to headquarters begging for permission to let the tanks push on. But his appeal had no effect. ‘You can never talk to a fool,’ Thoma later remarked. ‘Hitler spoiled the chance of victory.’

It is hardly surprising, considering the panzer generals’ hostile reaction to the halt order, that some of them concluded it was prompted by a secret political design. This impression was reinforced by General Rundstedt, whose headquarters the Führer visited during the morning of May 24 to discuss the halt order. After the war, Rundstedt told Liddell Hart that Hitler ‘deliberately let the bulk of the BEF escape, so as to make peace negotiations easier.’

To Guderian, on the other hand, the idea that Hitler purposely allowed the British to escape from Dunkirk was ‘an absurd theory.’ ‘It was by capturing the whole of Lord Gort’s forces,’ he argued, ‘that we might have brought the British to terms. To leave them with the units that would enable them to raise and provide the backbone of further armies was, on the contrary, tantamount to urging them to go on with the war and to strengthening their resolve.’

Yet that is exactly what happened. By halting the panzers, Hitler allowed the British to reinforce the Dunkirk perimeter sufficiently to permit more than 300,000 British and French troops to be evacuated to England over the next week and a half.

In effect, Hitler sabotaged Manstein’s plan when it was on the verge of producing complete victory over the Allies. Even though France was knocked out of the war soon after the German offensive resumed on June 5, the British refused to surrender. Hitler was compelled to initiate preparations for an invasion of England that summer. But due largely to the heroic efforts of the Royal Air Force, the Luftwaffe was unable to gain the prerequisite air superiority over the English Channel and the southern coast of England. As a result, Hitler was forced to postpone the invasion attempt indefinitely.

Hitler then committed his second major strategic blunder. Before Britain was defeated, he launched an invasion of Russia in June 1941. He thereby committed Germany to a two-front war, a mistake he had promised he would never be foolish enough to make. Had Britain not continued in the war following the debacle in France, Hitler’s forces might have succeeded in conquering Russia before the first snows of 1941 fell. But Britain’s refusal to surrender would tie up some 40 German divisions that otherwise could have seen action on the Russian Front and possibly helped Germany to defeat the Soviet Union.

Hitler’s inability to defeat Britain was due in no small measure to his failure to destroy the British army when he had the opportunity to do so. His sabotage of Manstein’s plan, by halting the panzers when Dunkirk was virtually undefended, was a mistake for which he, and Germany, would pay dearly.


This article was written by Ronald E. Powaski and originally appeared in the November 2003 issue of World War II magazine. For more great articles subscribe to World War II magazine today!