King Leopold III, commander of the Belgian Armed Forces in 1940, had a strategic dilemma. Both the French and the Germans sought to make war with each other on his soil. Both had war plans that called for advancement into Belgium to fight the main force engagement that General Gamelin, the French commander, and General Manstein, the German commander, hoped would eliminate the other.
Leopold did not wish for war, but his loyalties remain a subject of debate. With the war less than a year old in 1940, Neither the French nor the British had the will to fight another protracted battle of attrition that characterized World War I. Leopold made his decision against the wishes of his government cabinet — he would remain neutral.
Thus, despite better tanks, more planes, and nominally more men under arms, the Allies went into the Campaign in France on May 10, 1940 not as welcomed guests, but as invaders of Belgium. The government officials who recognized Germany as the greater threat to Belgium did what they could, opening the border for the Allied armies when the Germans struck, and eventually Leopold declared Belgium for the Allies. But precious time was up. Belgian and Allied units had never wargamed together, and each operated under essentially different commands with their own agenda.
Leopold and the Belgian Army hoped Fort Eban Emael, a modern breastwork of concrete and steel pillboxes, would hold up the Germans until Allied and Belgian reinforcements arrived. The Germans coped with the fort by dropping paratroopers, who used flamethrowers and explosives to destroy the gun ports and roast the Belgians. Some 400 were killed and the fort surrendered when the reinforcements came under heavy air attack by Stuka dive bombers.
With Fort Eban Emael gone, the Belgians had little time left. Allied men and machines poured into Belgium for the major battle that was expected, but the Germans were thinking in terms of a new war, while the Allies were ready to fight the last one. Fast-moving tank formations under Generals Rommel and Guderian broke out of the Ardennes and drove for the coast, cutting off the Allied front-line units and forcing the French to fight the tanks with their rear echelons. The Allied plans were doomed, but it would take four days for anyone to realize the German battle plan’s actual goals.