The Manstein Plan came after the initial Nazi Case Yellow or Plan Yellow was lost to the Allies on January 10th 1940, meaning Hitler needed to delay his assault on France. Leading to the Phoney war of 1940 it bought the German army time to rebuild and put a new plan in place, designed by Eric Von Manstein. This aimed to hit through the French lines via the Ardennes, either side of the 3 billion franc Maginot line and the Belgian border. What came next was the capitulation of France.