a rare photograph from tank landing trials conducted as part of the preparations for Operation Stahlengel, source: Flickr.com with permission of the publishing user, edited

That the Germans planned a naval invasion of Great Britain in 1940 is by now common knowledge. Operation Sea Lion — codename Seelöwe — was, however, postponed indefinitely in September 1940 and thereby effectively cancelled. Less well known is the fact that the Germans continued to work on plans for an attack on Britain, developing a completely different type of invasion. Which, truth be told, is hardly surprising. It is simply impossible to imagine the choleric and obstinate Hitler calmly accepting that something had not gone the way he wanted. It is therefore no surprise that simultaneously with the formal postponement of Seelöwe, the Führer tasked his generals with finding any path at all that would end with Britain conquered and occupied by German forces. "You must come up with something!" Hitler reportedly shouted at a Supreme Command conference. "Who exactly do you think I'm supposed to be at war with? France is defeated, and I have a treaty with Stalin... and I keep my treaties — Chamberlain can testify to that! Am I supposed to go and invade Greece?! And what would I gain from that? That might be interesting for Mussolini, perhaps."

The General Staff therefore set to work. The fundamental flaw of the original Seelöwe plan was the very fact that it was an amphibious operation. That meant troops, equipment, and supplies would have to cross the English Channel by sea. Even at this stage the invasion forces would be exposed to the danger of the British navy and air force. The operation would have to be preceded by a massive concentration of forces in the embarkation ports in France, which would certainly not escape the enemy's notice — the French Resistance would warn the British, if nothing else. Movement by sea is also very slow, giving the defenders more time to prepare to repel the attack. A naval invasion is moreover heavily dependent on sea conditions at the time and on the state of the tides. And there are not unlimited suitable landing beaches on the British coast, meaning the opponent could prepare in advance specifically to defend the most likely sectors.

Once ashore, units are like it or not confined to the established bridgehead, severely limiting their freedom of manoeuvre. The deployment of the large formations that German Blitzkrieg demanded would be very problematic, and with the sea at their backs there would be no possibility of a tactical withdrawal to more favourable positions should the situation require it. British ships could moreover continue to intervene in the land battle even after the landings, as the battlefield would remain within their gun range for a long time to come. That is already quite a list of drawbacks. Incidentally, all these anxieties of the German high command about a naval invasion were effectively confirmed by a war game simulation conducted by the British Royal Military Academy at Sandhurst in 1974. The result of that simulation was a catastrophic failure for Operation Sea Lion, with 45% casualties killed and wounded and 37% taken prisoner! One of the key factors leading to the invasion's failure in the simulation was precisely the ability of the British fleet to destroy a large proportion of the follow-up landing waves while still at sea — more than a third of German fatalities were projected to occur before the troops even reached the shore. (You can read more about this simulation HERE.)

a captured Universal Carrier fitted with rocket propulsion, preparing at the edge of the launch strip during Operation Stahlengel rehearsals; the soldiers are about to ignite the three rocket motors and take off — steering during flight was accomplished by swivelling the nozzles using the straps clearly visible in the photograph, source: Flickr.com with permission of the publishing user, edited

It is therefore no surprise that the German generals very quickly abandoned the idea of a seaborne invasion and began exploring a purely airborne one. The aim was to design it in a way that would allow a rapid transition to the proven German Blitzkrieg style of warfare. That meant delivering as many forces as possible, as quickly as possible, to a single location where the enemy least expected them, and which was suitable for the deployment of large armoured formations — from which they would then advance further through the British interior in the classic manner of ground Blitzkrieg. The chosen drop and assembly area was in the county of Suffolk, specifically the roughly triangular area formed by the towns of Halesworth, Wickham Market, and Diss. The area was flat, relatively sparsely populated, and had good roads leading in both intended directions of attack. The first part of the force was to advance westward from the assembly point, from Diss toward Peterborough, Leicester, and Birmingham — this thrust was intended to cut off the south of England from the rest of the country and prevent reinforcement from the north. The second axis of attack ran from Wickham Market south-west toward Ipswich, Chelmsford, and London. The invasion plan called for the massive use of transport aircraft to deliver both troops and heavy equipment to the site.

The generals presented their plan to the Führer at the end of 1940 and informed him that for the purposes of this operation, development of the large-capacity transport aircraft Messerschmitt Me 323 Gigant had already been initiated. Hitler was broadly pleased with the plan. He expressed concern, however, that even an air transport operation using conventional aircraft would not be fast enough, and that the British RAF would have time to respond and inflict heavy losses on the invasion forces before they even landed. He wanted to push the concept of lightning warfare to its logical conclusion and demanded a much faster means of aerial delivery. While heavy ground weapons were Hitler's true passion, he also followed the development of other types of military technology — and he was very well aware of the successes achieved since the 1930s by engineers Walter Dornberger and Wernher von Braun in the development of ballistic rockets under the codename Aggregat.

The results of the Aggregat programme were promising and the plans for the future were downright megalomaniacal. At that time, the first generations of rockets designated A1, A2, A3, and A5 had either been developed or actually test-fired. Work on the powerful A4 rocket was under way, and for the coming years an even larger and more powerful rocket, the A10, was planned — one that would be capable, when fired from Germany, of striking targets in the United States! Hitler's mind was made up. It would not be aircraft that would carry the invasion army to Great Britain — it would be rockets! Only then would the German attack be truly lightning-fast! The British air force would have no time to react. By the time the RAF fighters were airborne, German forces would long since be on British soil. And even if a few Spitfires happened to get in the way of the invasion rocket fleet — what could they do? They would have virtually no chance of threatening rockets travelling at such speed. The Führer was enthralled by the vision and ordered an immediate feasibility study for such an invasion.

Wernher von Braun with a model of the V-2 rocket with a Panzer IV attached; later calculations and tests showed that a single rocket was insufficient to transport a medium tank, source: Flickr.com with permission of the publishing user, edited

Within just one month, a further meeting was held on the subject, this time with rocket engineer Wernher von Braun in attendance. He was shown maps of the proposed landing area, asked about the expected numbers of troops and vehicles, the weight of the tanks, the timing of the whole operation, and many other details. Under a strict pledge of secrecy he took all the information away with him, along with the task of producing a feasibility report within the month. A debate then followed about what the whole operation should be called. The name Seelöwin (the female of the sea lion), suggested by Göring, was swept from the table because the new invasion had nothing to do with water. The final vote produced a winner with 15 votes: Stahlengel — Steel Angel.

For planning purposes, the invasion forces were divided into several groups whose transport requirements differed considerably. The first group was, of course, the infantry — 250,000 soldiers to be delivered to Britain essentially simultaneously. The next group comprised support vehicles of all types: primarily carriers for infantry, ammunition, fuel, and other war supplies. The final group included the fighting vehicles themselves — tanks above all, but also artillery. Each of these groups presented a specific set of problems to be solved.

The Aggregat programme had never developed rockets with any usable internal cargo space. It was therefore clear that the rockets would serve only as propulsion. The transported infantry, for example, would not be able to sit inside a rocket. The initial idea considered for the troops was individual transport using personal jetpacks — in German, Raketenantriebrucksack. After the first verification trials, however, this approach was ultimately rejected for two reasons. First, having that many soldiers in the air simultaneously would inevitably lead to mid-air collisions and casualties. Second, individual transport would require every single man to be trained in how to operate the rocket propulsion — which was organisationally and logistically quite complex. Even the very first experiments had shown that without such training, disaster was guaranteed. There were in fact "experts" who put their jetpack on backwards — such as the unfortunate soldier in the photograph below.

a photograph from jetpack (Raketenantriebrucksack) trials; the soldier in the photograph has put the device on backwards — if he were now to ignite the three small rocket motors, it would most likely drill him straight into the ground; the risk of such errors led to the abandonment of this method of transporting infantry, source: Flickr.com with permission of the publishing user, edited

It was therefore clear that infantry would have to be transported in some collective fashion. Attaching a rocket to an ordinary truck in which soldiers would sit was immediately ruled out. Standard canvas-sided lorries such as the Opel Blitz were simply not robust enough to survive this mode of transport. It was therefore decided that the infantry would travel in their armoured half-tracks, to which rockets of the necessary thrust would be attached. The fuel supply in the carrier rockets would be calculated to run out approximately over the target area, and the landing itself would then be accomplished by parachute. A similar plan applied to the transport of ammunition, fuel, spare parts, medical supplies, and other materiel — again using lightly armoured cargo vehicles with attached rockets and parachutes. For this purpose the captured British Universal Carrier presented itself as an ideal type.

Artillery weapons — whether conventional guns and howitzers or anti-tank guns — proved to be a major puzzle. At that time, the German army relied almost exclusively on conventional guns towed by wheeled or half-tracked prime movers, or by horses. The complete package of gun plus prime mover was too large to transport in a single piece — and horses were ruled out of rocket transport from the start. On the other hand, if gun and prime mover had to travel separately, twice as many rockets would be needed — and the numbers required were already enormous. The obvious solution was the exclusive use of self-propelled guns, which could travel as a single load. The greatest challenge, however, was undoubtedly presented by the tanks, as the heaviest of all the vehicles to be transported.

Von Braun took the latest A4 rocket — which would enter history under the designation V-2 — as the starting point for all his calculations. The calculations showed that to transport Sd.Kfz. 251 infantry half-tracks, the V-2 was actually more than powerful enough, and a set of several smaller, cheaper rockets would amply suffice. This solution moreover permitted a horizontal launch from the half-track's normal travel position. The V-2, by contrast, launched vertically, meaning a half-track attached to one would also have to be in a vertical position at the moment of launch. Since the Sd.Kfz. 251 had an open top, this was out of the question — the soldiers and their equipment would simply tumble out during the launch. The same applied to cargo carriers such as the already-mentioned Universal Carrier, which also had an open cab. For the Sd.Kfz. 251, a bank of six carrier rockets was therefore adopted, mounted three on each side of the vehicle. For the Universal Carriers, three slender rocket motors were positioned directly above the cargo compartment, naturally at the rear.

the Sd.Kfz. 251 armoured half-track fitted with six carrier rockets, enabling an almost vertical launch from the normal travel position, source: Bundesarchiv_Bild_101I-216-0417-09, Wikimedia, Creative Commons, edited

The tanks were a different matter. Even the V-2 was too weak for medium tanks such as the Panzer III and Panzer IV, and it therefore had to be used in tandem — simply put, two V-2 rockets had to be attached to each tank. Tanks would therefore launch vertically. Since tanks were fully enclosed, this did not present a fundamental problem. All objects in the interior — including ammunition — did of course need to be secured far more thoroughly. The crew seats also had to be modified and fitted with five-point safety harnesses to prevent injuries during launch and landing. Over the target area, the crew would detach the tank from the rockets, simultaneously deploying a set of enormous parachutes on which the tank would land. The rockets themselves — along with the additional fuel tank, to be discussed presently — would simply crash to the ground somewhere 20 to 30 km further on, which incidentally produced the welcome side effect of thoroughly confusing the enemy, who had no idea what was happening or where.

From a technical standpoint, the rocket invasion was therefore feasible. It would, however, require enormous preparation. Thousands upon thousands of rockets were needed — not only of the V-2 type but also of the smaller types already mentioned. Thousands upon thousands of half-tracks for infantry and cargo transport had to be produced, and all the invasion vehicles modified to accept the large landing parachutes. The manufacture of the parachutes themselves was, in the grand scheme of things, merely the cherry on top of the preparation cake. Towering above all other problems, however, was the question of fuel. Von Braun's calculations revealed the staggering fuel requirements of the planned rocket fleet. The worst case was, of course, the tanks. The Germans planned to deliver roughly two thousand tanks to Britain — and the transport of each one required approximately 50,000 litres of rocket fuel. This quantity did not even fit into the tandem of two V-2 rockets, so an additional separate oversized fuel tank had to be attached. This solution, incidentally, would inspire the Americans some thirty years later when building their Space Shuttles.

The total fuel requirement for the rocket invasion was estimated at a staggering 600 million litres! The V-2 used a propellant mixture consisting of 75% ethyl alcohol and 25% water. To produce ethyl alcohol in such quantities, however, Germany lacked both the factories and the wider infrastructure. They would first have to be built, and only then could production begin. That would mean several years' work — and Hitler had originally planned to carry out the invasion on 1 April 1941. The Führer therefore convened his General Staff and posed the central question: where to obtain sufficient quantities of ethyl alcohol quickly enough to produce 600 million litres of rocket fuel? After a long silence, one hand was tentatively raised and the Chief of the Army General Staff, Franz Halder, requested permission to speak. On the table in the middle of the room he unrolled an enormous map and planted his finger on the territory of the USSR.

a final check of the rocket motors before a test launch; the tests conducted showed, however, that these small jet engines were adequate for carrying an armoured half-track but simply too weak for tanks — even light ones, source: Flickr.com with permission of the publishing user, edited

The Russian fondness for vodka was already well known at the time. According to reliable estimates from German intelligence, alcohol consumption in the Soviet Union stood at approximately 15 litres per person per year, the vast majority of which was vodka. With an estimated population of 190 million, this meant consumption of some 2.85 billion litres of pure ethyl alcohol per year. From this it could be inferred that the immediate stock of alcohol held by Russian families in bottles in their own homes should more than suffice to cover the required 600 million litres of rocket fuel. Hitler listened to Halder and looked at von Braun. Von Braun confirmed that even ethyl alcohol at a concentration of around 50% could, with certain modifications, be used to produce the fuel.

Hitler thought for a moment and then said: "The Russians will never give us the vodka voluntarily. And if they did, they'd want so much money for it that it would be cheaper to just go and conquer the damned country!" At these words Hitler fell silent, and everyone in the room looked at each other. "To hell with the treaty! I never trusted that Bolshevik anyway!" the Führer spoke again. He immediately ordered the temporary postponement of Operation Stahlengel and instructed Halder to urgently prepare a plan for an attack on the USSR to be carried out before the summer of 1941. Yes — it is a little-known fact, but it is entirely true. Operation Barbarossa was nothing more to Hitler than the means to an end — the end being to crush the defiant British with that pompous Churchill at their head. Hitler was convinced he was simply popping over to the Soviet Union to pick up 600 million litres of alcohol, more or less as if doing a spot of shopping. He considered it a quick and easy operation — as his famous remark illustrates: "You only have to kick in the door and the whole rotten structure will come crashing down... and we'll take as much vodka as we want." A few months and it would be done, and then the Germans could focus exclusively on Britain.

In this connection, the origin of the codename for the attack on the USSR — Operation Barbarossa — also deserves explanation. The word Barbarossa is Latin for "red beard," which, you will surely agree, is a rather peculiar name. So how did it come about? When Hitler called on his generals to suggest a suitable codename for the planned operation, Field Marshal Keitel proposed that since the objective of the operation was to acquire alcohol stocks, a fitting designation would be Operation Red Nose (Unternehmen Rote Nase). Göring objected, however, that such a name would give away the operation's objective rather too obviously, and suggested using a less conspicuous Latin equivalent — Unternehmen Russus Nasus. This designation, however, appeared to point almost directly at Russia (Russland in German), and was therefore likewise deemed insufficiently concealing and too easily seen through. Hitler therefore ruled that while the red-nose idea was charming, the search for a sufficiently cryptic designation would have to move a few centimetres lower — from the nose downward to the beard. It would not be a red nose but a red beard, and since everyone had taken a liking to the Latin approach (they presumably felt it made them sound more educated), the now-legendary designation Unternehmen Barbarossa was chosen.

a truly unique photograph of a Panzer III fitted with the full rocket transport assembly consisting of two V-2 rockets and an additional fuel tank — Americans used a similar arrangement thirty years later when building the first Space Shuttle; note also the four large landing parachute bags on the sides of the tank, source: Flickr.com with permission of the publishing user, edited

Preparations for Operation Stahlengel therefore continued, almost invisibly to the outside world. Von Braun was designing smaller carrier rockets for light vehicles, testing the launch and flight of two V-2s joined in tandem with an enormous fuel tank in between, and trials were being conducted into landing tanks and half-tracks by parachute, and so on. Hitler and von Braun frequently spent long hours discussing details that interested the Führer. Meanwhile, Hitler was already dreaming of how in a few years, with even more powerful rockets, he would send his forces across the ocean to the United States. It was precisely from these visions that Hitler arrived at the decision that all future German tank types would have to feature an aerodynamic design, so that they would have less air resistance in flight and save at least a little of that blasted rocket fuel. The first such type, the famous Panther, appeared the very following year. Yes — it is as stated: the true reason for its sloped front armour was better aerodynamics, and the improved resistance of such armour to shellfire was in this case merely a pleasant side effect. And what about the later tank destroyer, the Jagdpanther? Its rigorously aerodynamic design can leave no one in any doubt that it was conceived for smooth flight at very high speed!

The quest for Russian "fuel" began, as we know, on 22 June 1941. Behind the combat units advanced special requisitioning commandos — the Beschlagnahmengruppen. Their members went from house to house searching for one thing and one thing only: vodka. In the first weeks everything went fairly smoothly. The Soviet army was not only caught completely off guard by the German attack, but most of its soldiers were frankly rather indifferent to it. Life under Stalin or under Hitler? A tyrant is a tyrant. The only thing that made them fight at all was the ever-present political commissars who shot all deserters on the spot. In the western regions of the USSR the local population actually welcomed the German army. Before long, however, a terrible and truly dreadful whisper began to spread among the Russian population. "They took everything! Absolutely everything! In Lvov, in Minsk, in Riga! You understand — absolutely everything! Those poor people there have nothing left at all!"

Fear spread like a plague. Old women crossed themselves before their holy icons; some men tried to bury their bottles of vodka in their gardens; others hurried to drink them. Stalin decided to harness this fear. In his famous address to the nation on 7 November 1941 he made it plain for all to hear: "Do not imagine, comrades, that if the Germans defeat us, everything will essentially remain as you are accustomed to. The fascist beasts do not merely wish to steal our land — they wish to take our entire way of life! They will seize all your vodka, and then make you work into the bargain!" An unprecedented wave of hatred towards the enemy surged through the Soviet people. Every Russian was now prepared to fight, and if necessary to lay down his life. "We are not doing this just for ourselves — we must save the vodka for our children too!" the commissars exhorted before each attack, and the soldiers of the Red Army suddenly had absolute clarity: the Germans simply had to be driven back, whatever the cost.

the special commandos known as Beschlagnahmengruppen confiscated vodka across the USSR; lorries then collected it and brought it to railway stations, from where it travelled in tanker wagons to Germany; here the decanting from demijohns into tankers is under way, source: Bundesarchiv_Bild_101I-186-0166-04A, Wikimedia, Creative Commons, edited

In the first weeks, dozens of tank wagons full of the precious liquid arrived from the occupied Soviet territories every day. As the Soviets grew ever more skilled at hiding their liquid gold, however, the deliveries reaching the Reich grew smaller. Things were also becoming increasingly complicated on the military front. By the end of 1941, the Germans had collected enough vodka to produce barely a hundred million litres of rocket fuel, and the whole war in the East showed no sign of ending quickly or easily. Hitler raged, but could do nothing. The vodka "procurement" in Russia had simply not worked out. Instead of swiftly requisitioning the required alcohol, the Germans had been dragged into prolonged and exhausting fighting. By spring 1942, even Hitler himself had reluctantly to admit that the execution of Operation Stahlengel was not — and would not in the foreseeable future be — possible. "Well then — load those damned rockets with explosives and send them to London!" the Führer resigned himself.

History knows no "what ifs," so we cannot be certain today how Operation Stahlengel would have turned out had it ever taken place. What is certain is that the Germans prepared for it with genuine thoroughness and left nothing to chance.

1st April 2025, HAPPY APRIL FOOLS' DAY!