The long anticipated German attack on France and the low-countries began in the early morning hours of May 10, 1940. The German attack on the west was launched with pre-emptive air attacks on Anglo-French airfields, destroying many allied aircraft on the ground and giving the Luftwaffe near total air superiority. This not only contributed to the Allied shock, but also allowed the German airforce to provide reconnaissance, close air support, and air-transport to ground forces.

Meanwhile, Army Group B thrust into the Low Countries in the north in an effort to deceive the allied commands by convincing them that the German attack was a refined version of the 1914 "Schlieffen Plan." This move was exactly what the Allies had planed for and they quickly deployed the bulk of their mobile forces, including the British Expeditionary Force, into Belgium in accordance with Plan D. In reality the Germans northern attack was an elaborate feint!

Of more importance was the thrust by Army Group A through the dense Ardennes forest, in accordance with Manstein's "Sichelschnitt Plan." The Ardennes area was less than ideal country for armor and limited the seven panzer divisions to a slow advance along the narrow, forest-lined roads. But the Allied commitment in the north combined with the lack of fixed defenses in the Ardennes gave the German panzer troops the time needed to deploy. Late on May 12th, the leading units of the XV Panzer Corps reached the River Meuse near Dinant. 24 hours later the 7th Panzer Division was across and driving into the rear of the French divisions still guarding the Ardennes area. In the south the XLI and XIX Panzer Corps forced crossings at Montherme and Sedan respectively on the night of the 14th, completely flanking the stunned Allied defenses. Limited Allied air attacks tried desperately to destroy the Meuse River bridgeheads but suffered devastating losses. By 15 May, the panzer divisions had reorganized and rearmed and began to thrust at full speed toward the Channel coast with it's vital ports.

As the Allies tried desperately to recover, the divisions of Army Group B continued to press from the north to keep the Allied formations engaged in Belgium. The panzers of Army Group A were able to drive through disorganized resistance to the coast, severing Allied links between the frontline divisions and the reserves. By May 21st the Allied armies in Belgium had been surrounded and cut off from France. With no other choice but annihilation, plans were made to withdraw toward the coastal town of Dunkerque, where the British navy would evacuate the troops minus their equipment. By then Holland and Luxembourg had surrendered. Belgium soon followed and capitulated on May 28th.

Between 26 May and 4 June over 338,000 Allied troops were picked up from the beaches at Dunkerque. But any hope of redeploying them south into France was made impossible by low morale and the loss of their heavy equipment. Once Dunkerque had been captured, most of Army Groups A and B turned south where they met little resistance from the demoralized French Army. On 14 June Paris fell and on the 22nd, the French government asked surrender terms. A cease-fire went into effect on 25 June, little more than six weeks after the start of the German attack.

The Wehrmacht had achieved a stunning victory by using a combination of surprise and continuous movement known as the blitzkrieg. While casualties had not been light for the Germans, losses totaled more than 137,000, France had been knocked out of the war and Britain was left alone to face the battled tested German army. With the coastal areas of France and the whole of the Low Countries occupied, Hitler could afford to turn his attention to the east and the Soviets. By the end of June 1940, the German high command began to make plans for the invasion of England. For the undefeated Wehrmacht, anything seemed possible.