The Battle of Belgium (10-28 May 1940) was an offensive campaign of Nazi Germany during World War II that saw the German Wehrmacht overrun Belgium in an eighteen-day campaign involving the first tank battle of the war (at the time, the largest in history), the first strategic airborne operation involving paratroopers, and heroic Belgian resistance that was commended even by the Germans. Nevertheless, Belgium was occupied, and it would remain so until September 1944.
The World War I-era Schlieffen Plan called for Germany to invade France through Belgium so as to divert troops from the southern sector north, as well as to bypass French defensive positions on the Franco-German border. During World War II, with Germany and France again being on opposite sides of the conflict, Erich von Manstein drafted a plan that involved a "sickle cut" through the Low Countries to invade France. The two plans were similar, with both of them involving an invasion of France through Belgium. This time, however, Allied troops were prepared for an invasion.
At dawn on 10 May 1940, German Luftwaffe planes bombed airfields in the Netherlands, Belgium, and France, establishing immediate air superiority over the Low Countries. A second wave took out known headquarters, communications centers, railroads, and military camps, and this was followed by German fallschirmjaeger landings at crossings over the Meuse River in the Maastricht area. In addition, a small glider-borne force was used to assault the key fortress of Eben Emael, near the junction of the Meuse with the Albert Canal. Gerd von Rundstedt's Army Group A crossed the Belgian border as Fedor von Bock's Army Group B invaded the Netherlands, and three French armies and the British Expeditionary Force moved into Belgium to establish themselves in a defensive lyne along the Dyle River. The Germans thrusted towards Brussels, while panzer spearheads forced their way through the Ardennes and brushed Belgian forces aside. Luftwaffe attacks against airfields and other targets continued, and the Germans wore down the Allied fighter strength in fierce battles. The French called on the British to send more fighters across the English Channel, and Prime Minister Winston Churchill ignored RAF Fighter Command chief Hugh Dowding's advice and dispatched further Hurricanes to Belgium. The RAF and Belgian fighter-bombers attempted to bomb the Maastricht bridges to halt the German advance, but most of the planes were shot down and the bridges remained intact.
By 12 May, the German tanks had reached the east bank of the Meuse, and the tanks crossed the river the next day, breaking through the French defenses on the other bank and sweeping west towards the Channel. To the north, elements of the successful Army Group B closed up to the Dyle Line, which initially held them. However, the westward rampage of the panzers threatened to cut off the Allied armies in Belgium, so they began to withdraw their troops on 16 May. On 17 May, Brussels fell to the Germans, and a French armored division commanded by Charles de Gaulle was held off in a failed counterattack. Hitler briefly halted his panzer divisions to allow for the infantry to catch up, and the Allies fell back in an orderly fashion. Civilian refugees clogged up the roads that the troops wanted to use, and the Luftwaffe machine-gunned refugees from the air. On 19 May 1940, French commander Maurice Gamelin was replaced as commander-in-chief by Maxime Weygand, but it was too late; German armies reached the Somme River on 20 May, advancing into France. The remnants of the Belgian Army retreated into a tight pocket in northern France as the northern Allied forces were pushed back, and Luftwaffe dominated the skies during daylight hours. The German advance was slowed as supply routes were overextended, and Army Group A's advance was halted on 23 May. Meanwhile, Army Group B took Boulogne on 25 May and Calais on 27 May, and the Belgian army found tehmselves in a repeat of 1914, holding just one strip of their country ont eh coast as they retreated. The endless retreats sapped Allied morale, and there were rumors of fifth columnists and disguised German paratroops, some apparently dressed as nuns, operating in their rear. On 25 May 1940, the Belgian high command warned the French and British that its remaining forces, which were on the left flank of the forces facing Army Group B, could not hold out for much longer. The commander of the BEF, Lord Gort, decided to withdraw to Dunkirk without telling the other Allied commanders, and the Belgians were forced to surrender on 28 May 1940, having been abandoned by their allies. The Belgian government and army was established in exile, with the British evacuating British, French, and Belgian troops by sea at Dunkirk.