Best of all, the fort's earthen roof made artillery attacks and aerial raids damn nigh pointless. Bombing Eben-Emael was like bombing a well-armed mountain.
"Nice going, Hans. Now you've pissed off the mountain."
The Fatal Flaw:
The fort could be taken out with just a handful of troops, assuming they could arrive there alive. Which might have been OK, since the whole design should be based on keeping that from happening. But it also turned out that the fort was unintentionally designed to roll out the red carpet for troop-carrying gliders. And we're not talking some fancy, heavily armed wunderwaffe of a glider; no, we mean the unarmed, "prone to flying apart in a whimsical puff of sticks and fabric if you look at 'em funny" type.
Bundesarchiv, Bild 101I-567-1519-18 / Stocker / CC-BY-SA 3.0
Seconds before direct sunlight caused it to burst into flames.
So in the wee hours of May 10, 1940, 11 German Ju 52 planes hauled eleven DFS 230 gliders stuffed with a massive invasion force of 74 paratroopers into the air and flung them toward Eben-Emael like history's deadliest paper airplanes. While the earthen roof of the fort rendered it relatively bomb-proof, it also made for a perfectly cushy landing surface for the gliders, which eschewed wheels in favor of nose skids wrapped in barbed wire to land in a space as short as 20 yards, which is the aircraft equivalent of stopping on a dime.
Once down, taking out the invincible fortress was comically easy: The invaders spilled from the gliders and used hollow charges to funnel devastating explosions down into the base like little reverse volcanoes.
via Wiki Commons
As if volcanoes weren't scary enough in the regular direction.