The Manstein Plan or Case Yellow () also known as Operation Sichelschnitt (, from the English term sickle cut), was the war plan of the German armed forces () during 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, which 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. Name The Manstein plan has often been called Operation Sichelschnitt, 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 N°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