The fortress at Eben Emael, built upon granite, was set upon a ridge some 50 metres above the surrounding countryside. It was protected to the east and to the northeast by natural water defences: the Meuse River and the Albert Canal. To the southwest and to the south there were artificial defences of antitank ditches and barbed wire. The fortress was the strongest part of the Liège defence system, and the heavy guns of its main armament dominated the area.
This fortress, this barrier to any advance by the Sixth Army, was the objective for a special force, and only they could take it. Eben Emael was impregnable to gunfire. Conventional infantry attackers would first have to cross the Albert Canal and climb the high bank to reach the plateau on which the main defences stood. These forts and blockhouses, all mutually supporting, would have to be attacked one by one, until the whole complex was in German hands. The Belgians, of course, would react violently to such assaults, and by a determined defence could not only inflict horrifying casualties, but more importantly, would delay the timetable of the advance until the military initiative had perhaps passed to the Allies. They sure could have used crisis intervention training in 1940!
To take out such a special target required picked men using unusual weapons. Germany had both! In a modern refinement of the hollowcharge grenade, the Army had a weapon capable of destroying the armoured cupolas of Eben Emael. If a horizontal attack by conventional infantry advancing across open ground could not succeed, a vertical assault by paratroops or gliderborne soldiers armed with their hollowcharge grenades might be a practical if radical solution.
The establishment of a Corps Parachute Engineer Battalion.
Thus far we have found the weapons that will destroy the guns and the way in which the explosives can be brought to the scene of the action. But what of the men who were to carry out the operation? Shortly after the outbreak of war the Airforce took on to establishment the 7th Parachute Division, and it was the highly trained paratroops of that formation who were to carry out the mission.
From conferences and discussions among the Commanders of the Paratroop Division, it was soon established that a landing by parachute offered scant chance of success. Troops air dropped by parachute were often dispersed over a fairly wide area on landing, and the target zone of Eben Emael was only 1,000 metres long by 300 metres wide at its maximum point. Nor was parachute design so sophisticated that the troopers could manoeuvre themselves as precisely as they can today. The prospect of the widely separated assault troops having first to concentrate before conducting the assault was daunting. Victory at Eben Emael would depend upon a concentration of forces and fast action. Dispersal would lose the surprise factor that was all important.
The alternative to dropping parachute troops was to land gliders carrying the soldiers directly into the fortress area. This solution prompted a new question. Did Germany have glider pilots so skilful and proficient that in almost total darkness they could not only locate the small, triangular site of Eben Emael, but could land at precise points within its small area? The answer was that there were some Airforce and civilian pilots whose skill was internationally recognised and who could pass on those skills. For other flyers to reach that level of expertise would need long and hard training, but at the end there would be a large number of proficient men ready to meet the unusual challenges which the operation would demand.
The final point was that a nighttime landing was impossible; a minimum of light was essential. Thus the glider landings could not take place during the night nor at the onset of night, but either in full daylight or at first light. The entire operational plan of the German Army was thus tied to the landings by Parachute Assault Detachment Koch and, more specifically, to the success that the troops at Eben Emael would achieve.
The DFS 230 assault glider, the type of machine which carried German paratroops into action at Eben Emael, the invasion of Crete, and the rescue of Mussolini.
Under conditions of the greatest secrecy the glider pilots were taken to Hildesheim where dummy forts had been set up and upon which they practised the techniques of landing on small target areas. It was soon found that landing distances were too long. When the operation took place there would be eleven gliders all landing more or less simultaneously. It was essential for the pilots to achieve the minimum landing distance if collisions between the machines were to be avoided. Experiments showed that barbed wire wrapped round the slide under the aircraft’s belly could reduce the landing run to an acceptable length.
A training flight for the gliders of the Parachute Group which carried out the attack on Belgium during May, 1940.
At the same time as the pilots were improving their skills at Hildesheim, the paratroops had progressed from rehearsing rapid exits from gliders to the use of hollowcharge grenades, practising on fortifications in the former Czech defence line, which were similar in design to the constructions at Eben Emael. Finally, in the early spring of 1940, the two groups, glider pilots and paratroops, undertook joint exercises, practising by night and by day until their individual skills had been blended to perfection. The pilots were all able to land their machines, even in half light, to within twenty metres of a designated point, while the parachutists took only seconds to burst out of the wooden gliders and go straight into action. By the time that this stage of perfection had been reached, Operation Yellow was in the final stages of preparation. The day and time for the campaign had been fixed: 05.30 on 10th May! Five minutes before that time the gliders would have made their silent landings upon Belgium, and the war in the west would have begun.
In the opening hours of the campaign it was important not to alarm the Belgians. So as to give no hint of the impending attack, it was planned that the Ju 52s which were towing the gliders would maintain radio silence. They would not be directed towards the target by radio, so a means of ensuring correct direction had to be improvised. The route to the frontier would be lit by a chain of beacons forming a flare path which would guide the pilots as they flew very high through the dark May night towards the border. While still over German territory and at 2,100 metres, the Ju 52s would cast off their towropes and the wooden gliders, each filled with a troop of parachutists, would glide towards the fort, some 30 kilometres away. The troops would begin their tasks, and five minutes later the great mass of Armies, Corps, and Divisions of the German Army would advance. Behind the gliders and in front of the Army would come the assault waves of the Airforce. At H-Hour + 15, Stukas would swoop, bomb, and destroy the enemy, while transport aircraft would drop dummy figures of parachutists to cover the real landings and to create the maximum confusion.
We must now remove our concentration from Eben Emael and see the attack upon it as part of a larger airborne operation whose principal task it was to ….. enable Sixth Army to pass ….. without delay. Accepting that the assault upon Eben Emael would be successful, the corollary was the capture of certain bridges across the Canal at Veldwezelt, at Vroenhoven, and at Canne. These bridges, as well as the fortress of Eben Emael, were the objectives of the parachutist assault detachment commanded by Captain Koch. All attacks would be gliderborne, and all would take place simultaneously. To each of the four assault groups a codename was given: Iron, Steel, and Concrete. To First Lieutenant Witzig’s Eben Emael commando was given the codename Granite.
The bridges would be captured by rapid assault before they could be blown, and the concurrent seizure of the fort would prevent its guns from bombarding the bridges or from firing upon the units of Sixth Army as they swept across the Meuse and the Albert Canal. Parachute Assault Detachment Koch was made up of 11 Officers and 427 Noncommissioned Officers and men. This total included 42 glider pilots who, in addition to their specialist flying skills, had been trained in infantry warfare so that they could take part in the ground fighting. Koch’s orders to First Lieutenant Witzig, Commander of Granite detachment, were simple and direct. They concluded with the words ….. you will put out of action the armoured cupolas, casemates, and antiaircraft positions. You are to destroy the enemy’s resistance, and to defend the gains you have made, until relieved …..