The Manstein plan was the war plan of the German armed forces () for the Battle of France in 1940. The original invasion plan was an awkward compromise devised by General Franz Halder, the chief of staff of (OKH, Army High Command) that satisfied no one. Documents with details of the plan fell into Belgian hands during the Mechelen incident on 10 January 1940 and the plan was revised several times, each giving more emphasis to an attack by Army Group A through the Ardennes, that progressively reduced the offensive by Army Group B through the Low Countries to a diversion.
In the final version of the plan, the main effort of the German invasion was made against the Ardennes, the weakest part of the Allied line, where the defence was left to second-rate French divisions in the Second Army and the Ninth Army, on the assumption that the difficulty of moving masses of men and equipment would give the French plenty of time to send reinforcements if the area was attacked. The Seventh Army, which had been the most powerful part of the French strategic reserve, had been committed to a rush through Belgium to join with the Dutch Army to the north, in the Breda variant of Plan D, the Allied deployment plan.
Nomenclature The Manstein plan has often been called Operation , a transliteration of "sickle cut", a catchy expression used after the events by Winston Churchill. After the war, German generals adopted the term, which led to a misunderstanding that this was the official name of the plan or at least of the attack by Army Group A. The German name was Nr. 4, (Campaign Instruction No. 4, Case Yellow) issued on 24 February 1940 and the manoeuvre through the Ardennes had no name.
Background
The Manstein plan was a counterpart to the French Dyle plan for the Battle of France. Lieutenant-General Erich von Manstein dissented from the 1939 versions of (Case Yellow), a plan for an invasion of France and the Low Countries, devised by Franz Halder. The original N°1, (Campaign Instruction No 1, Case Yellow), was a plan to push the Allied forces back through central Belgium to the Somme river in northern France, with similarities to the 1914 campaign of the First World War. On 10 January 1940, a German aircraft carrying documents with parts of the plan for crashed in Belgium (the Mechelen Incident) prompting another review of the invasion plan. Halder revised to an extent in N°3, and Manstein was able to convince Hitler in a meeting, on 17 February, that the should attack through the Ardennes, followed by an advance to the Channel coast.
Prelude
Manstein, chief of staff of Army Group A, had originally formulated his plan in October 1939 in Koblenz on the instigation of his commander, General Gerd von Rundstedt, who rejected Halder's plan, partly through professional rivalry and part because it could not inflict a decisive defeat on France. Manstein first thought to follow annihilation theory (), envisaging a swing from Sedan to the north, rapidly to destroy the Allied armies in a cauldron battle (). When discussing his intentions with (Lieutenant-General) Heinz Guderian, the commander of the XIX Panzer Corps, Guderian proposed to avoid the main body of the Allied armies and swiftly advance with the armoured divisions to the English Channel, taking the Allies by surprise and cutting their supply routes from the south. Manstein had many reservations about the proposal, fearing the long open flank to the south that would be created by such a bold advance. Guderian managed to convince him that the danger of a French counter-offensive from the south could be averted by a simultaneous secondary spoiling offensive southwards, in the general direction of Reims.
When Manstein first presented his ideas to OKH, he did not mention Guderian and made the attack to the north the main effort, with a few armoured divisions protecting the left flank of the manoeuvre. The changes were included because the original conception was too bold to be acceptable to many generals, who also considered that Guderian too radical; Halder and Walther von Brauchitsch rejected the Manstein concept. Reformulating it in a more radical sense did not help. Manstein and Halder were rivals; in 1938 Manstein had been the successor of the chief of staff Ludwig Beck but had been ousted when the latter was disgraced over the Blomberg–Fritsch affair. On 1 September 1938, Halder, rather than Manstein, had replaced Beck. In late January, Halder got rid of Manstein by having him promoted to the command of XXXVIII Corps in east Germany.
In late January, Lieutenant-Colonel Günther Blumentritt and Major Henning von Tresckow, on Manstein's staff, contacted Lieutenant-Colonel Rudolf Schmundt (an old acquaintance of Tresckow) the army attaché of Adolf Hitler, when he was visiting Koblenz, who informed Hitler of the affair on 2 February. Having found the Halder plan unsatisfactory from the start, Hitler ordered a change of strategy on 13 February in accordance with Manstein's thinking, after having heard only a rough outline. Manstein was invited to the Reich Chancellery in Berlin to meet Hitler on 17 February, in the presence of Alfred Jodl and Erwin Rommel. Though Hitler felt an immediate antipathy against Manstein for being arrogant and aloof, he listened silently to his exposition and was impressed by Manstein's thinking. Hitler remarked after Manstein had left, "Certainly an exceptionally clever fellow, with great operational gifts, but I don't trust him".
Plan
Manstein took no more part in the planning and returned to eastern Germany. Halder had to revise the plan again, which became N°4, . The new plan conformed to Manstein's thinking in that Army Group A would provide the main thrust of the invasion through the Ardennes in southern Belgium. After crossing the Meuse River between Namur and Sedan, Army Group A would turn north-west towards Amiens, as Army Group B executed a feint attack in the north, to lure the Allied armies forward into Belgium and pin them down.
The revision was a substantial change in emphasis, in which Halder no longer envisaged a simultaneous secondary attack to the west but made it the main effort (). The dash for Abbeville was removed, river crossings were to be forced by infantry and there would be a long period of consolidation by a large number of infantry divisions crossing into the bridgeheads. The armoured divisions would then advance together with the infantry, not in an independent operational penetration. Halder rejected the idea of forestalling the French with a simultaneous attack to the south to occupy the assembly areas that the French would use for a counter-offensive.
Battle
Five panzer divisions of advanced through the Ardennes; XIX Panzer Corps with three panzer divisions on the southern flank towards Sedan, against the French Second Army. The XLI Panzer Corps with two panzer divisions on the northern flank, advanced towards Monthermé, against the French Ninth Army (General André Corap). XV Corps moved through the upper Ardennes towards Dinant, with two panzer divisions, as a flank guard against a counter-attack from the north. From 10 to 11 May, XIX Panzer Corps engaged the two cavalry divisions of the Second Army, surprised them with a far larger force than expected and forced them back. The Ninth Army, to the north, had also sent its two cavalry divisions forward, which were withdrawn on 12 May, before they met German troops.
Corap needed the cavalry divisions to reinforce the defences on the Meuse, because some of the Ninth Army infantry had not arrived. The most advanced German units reached the Meuse in the afternoon; local French commanders thought that the German parties were far ahead of the main body and would wait for it before trying to cross the river. From 10 May, Allied bombers had been sent to raid northern Belgium to delay the German advance, while the First Army moved up but attacks on the bridges at Maastricht had been costly failures (the bombers of the RAF Advanced Air Striking Force were reduced to aircraft by 12 May).
Against the plan, Guderian and the other panzer generals disobeyed their orders and quickly advanced to the Channel. The panzer forces captured Abbeville and then fought the Battle of Boulogne and the Siege of Calais, only temporarily being halted by orders from Hitler on 17, 22 and 24 May. After the halt orders the panzer forces advanced to the North Sea coast and fought the Battle of Dunkirk. The Manstein plan devastated the Allies, whose armies were cut in two, those in the north being encircled by Army Groups A and B, leading to the surrender of the Belgian Army and Operation Dynamo, the evacuation of the BEF and French forces from Dunkirk. Defeat in the north and the lack of mobile reserves led to the defeat of the remaining French and British forces in and the Armistice of 22 June 1940.
Aftermath
The success of the German invasion surprised everyone; the Germans had hardly dared hope for such a result. Most generals had vehemently opposed the plan as being much too risky; even those supporting it had mainly done so out of desperation because the geostrategic position of Germany seemed so hopeless. Two of the most prominent were Hitler and Halder; Hitler had not liked Halder's original plans and had suggested many alternatives, some of them bearing a resemblance to the Manstein plan, the closest being a proposal made by him on 25 October 1939. Soon, Nazi propaganda began to claim that the victory was a result of Hitler's military genius; Hitler said,
After the war, Halder claimed he was the main instigator of the German plan, supporting this with the fact that he had begun to consider changing the main axis to Sedan as early as September 1939 and that Manstein's original proposal was too traditional.
The Manstein plan is often seen as either the result of or the cause of a mid-20th century Revolution in military affairs. In the former hypothesis, expounded by J. F. C. Fuller and Basil Liddell Hart immediately after the events, the Manstein plan is presented as a result of the evolution of German military thinking since the First World War by Hans von Seeckt and Guderian, adopting the ideas of Fuller or Liddell Hart. If true, an explicit Blitzkrieg doctrine would have been established by 1939 and been the basis of the plan for the Invasion of Poland; the Manstein plan would have been its most spectacular implementation. Blitzkrieg theory would have been reflected in the organisation and equipment of the army and and would have been radically different from those of France, Britain and the Soviet Union, except for the contributions of individuals like Mikhail Tukhachevsky, Charles de Gaulle, Fuller and Liddell Hart. That the earliest plans by Halder or Manstein and the final plan by Halder did not conform to this doctrine is an anomaly, to be explained by circumstances.