When Germany invaded Poland, they did so by gathering more than a million men along the Polish border. Britain and France had previously pledged support to Poland if Poland were ever invaded by Germany. In fact, the French had a treaty with Poland which stated, “…France would launch an offensive against the Germans…no later than fifteen days after mobilization.” Unfortunately, France (and Britain) asked Poland not to muster their troops so as to not aggravate the Germans. Poland agreed and when the Germans did attack, the Polish were only partially prepared.
The French were defeated quickly because the German’s had intelligence information that indicated the French expected the Germans to invade from the north. But, the German’s invaded from both the north and south. They used the Luftwaffe to attack Belgium, Holland and northern France. This drew soldiers toward the north. Simultaneously, the German’s attacked with Panzers in the west and south.