General Franz Halder worked up the plans for the invasion of Poland. Incidentally, Halder had made plans to remove Hitler from power before the war. With Czechoslovakia ceded to Germany without a fight, war was averted and Halder's plans were abandoned. After the invasion of Poland, he sought support in a plan to curtail further offensives. Finding no helpers, over a span of several weeks, he carried a pistol in his pocket to meetings with Hitler, intending to assassinate him but never following through. Halder died in 1972.
General Walther von Brauchitsch directed the invasion of Poland, modified the plans for the invasion of France, and would have lead the invasion of England were it to go forward. He died in 1948 before he could be tried for war crimes.
But, back to the topic at hand:
Germany knew the French knew this. So, the plan for the invasion of France primarily involved dividing the allies into smaller, easily chewable bits. On May 10, 1940, they launched the invasion, completely bypassing the Maginot Line, invading Holland, Belgium, and Luxembourg. Allied forces positioned here to aid France once the battle was begun were taken completely by surprise. Holland fell in four days. Brussells was taken three days later. Just two days after that, the German 'sickle' completely encircled allied forces in a tiny pocket of land in Belgium. Plans called for Germany to press in and destroy allied forces completely.
Then, Hitler balked. Debate as to why he ordered a halt to his forces will continue beyond our lifetimes. Was he worried he was moving too fast, out-pacing supply lines, and exposing his flank to France? Belgium had a 'soft' border with France. This was the point of the invasion plan. Now that it was his territory, was this the time to exert his will on men who should know that they served him always? Or, this early, was it a hint that further interference with his officers' plans, and poor decisions, would later prove more and more costly as the war became prolonged.
Whatever the reason, the German might halted short of pushing a massive allied army into the ocean. Britain rescued over 300,000 men using 900 small craft. These men would return to England to rest and rearm and wait for the time they could return to the mainland and take it back from the invaders.