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 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 victory over 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, 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 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 instead of Manstein had replaced Beck. In late January, Halder got rid of Manstein by having him promoted commander of XXXVIII Corps in east Germany. In late January, Lieutenant-Colonel Günther Blumentritt and Major Henning von Tresckow, part of Manstein's staff, contacted Lieutenant Colonel Rudolf Schmundt (an old