Belgium's Fort Eben-Emael was the crown jewel of the country's defense from invasion, boasting huge gun emplacements, defensive ditches and canals, and hundreds of artillery troops, all to protect the heartland and capital. And the whole thing fell to 87 German paratroopers after barely a day of fighting from May 10-11, 1940.
The fort was built in the early 1930s to prevent the exact situation it faced in 1940: an invasion of the country from the east. It had large guns to sweep fire across three key bridges that would be vital to an invasion. The bridges were also wired for demolition in case the defenders and the fort couldn't keep the enemy from them.
Defensive canals, barbed wire, and anti-tank ditches made a land assault nearly suicidal, especially since the thick steel and concrete walls could shrug off most munitions launched by artillery or tanks of the day.
A few anti-aircraft guns were present on top of the fort and cupolas — guns with large domes to protect the crews — could fire across the top and kill any attackers who landed there.
But the fort was vulnerable to airborne assault. It had been constructed by digging into an existing large hill, and the miles of tunnels and thick walls made it tough to assault on foot, but did almost nothing to protect it from the sky.
And that's how the Germans got in. A special force of 420 paratroopers trained for six months in absolute secrecy to take the three bridges and the fort. The highly complex operation was risky but could save the German Army weeks or months of fighting if successful.
Three assault forces would hit the bridges and attempt to take them from the defenders while a fourth would hit the fort and prevent the guns from firing on the others. The assault force hitting the fort was carrying a new weapon of war to cut through the defenses, shaped charges.
But, the highly trained and well-armed commandos at the fort would be outnumbered nearly 10 to 1.
The Germans landed on the fort in gliders specially modified to stop in the short space, and German paratroopers rushed out to hit the defenders. Belgian gun crews, who knew a probable assault was coming, quickly opened fire — but they didn't have the canister shot that could quickly decimate the paratroopers.
Instead, the paratroopers were able to rush improperly maintained machine guns as they misfired and other gun crews as they reloaded. One of the defensive guns was taken out when a paratrooper threw a stick of dynamite through a small opening. Two others were destroyed by the special shaped-charge explosives. One crew was killed by a flamethrower.
And there were less defenders than there should have been. The fort relied on conscripts to flesh out its ranks, and many had finished their period or been pulled away to positions in the Belgian Army. Other troops were sick or on leave.
Within the first 10 minutes, the paratroopers had taken out nine defensive positions and forced many of the defenders to go underground behind barriers. Within 15 minutes, the Germans had neutralized the major defenses that threatened the fort attackers, as well as many of the guns that could hit the bridges.
The Belgians didn't accept this laying down, of course. Soon after the attack began, the fort commander ordered nearby artillery to fire on the fort, killing some of the German attackers.
But the Germans sheltered in the wrecked cupolas and other positions and rode out the worst of the artillery.
As the Luftwaffe sent planes to silence the Belgian guns, the paratroopers used their shaped charges and other weapons to seal off exits from the fort and to wreck the few remaining positions that could fire outside.
And the bridge crews had successfully captured two bridges intact and one more that was damaged but repairable. Only 28 hours after the start of the attack, the road into Belgium was open.
The paratroopers had suffered six dead and 15 wounded by the time that the Belgian troops began surrendering.
The attackers all received high awards for valor and Hitler captured the country soon after.