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The V-3 Cannon: Hitler’s Unfinished Mega-Gun

As World War II progressed it quickly became clear that Adolf Hitler and his Nazi minions would not have everything their own way. Yes, the early years saw the German army crush all that came before it, but with the disastrous Russian adventure and the massive build-up in Britain that would eventually become Operation Overlord, the Nazis knew they had a real fight on their hands. And desperation often leads to drastic measures. 

Cruise missile Fieseler Fi 103 (also known as a Vergeltungswaffe [Vengeance Weapon] 1, or V1) is pulled by soldiers on sledges to its launching position. by Bundesarchiv is licensed under CC-BY-SA

Chances are you may already know about the V1 and V2 weapons that began raining down on Britain shortly after D-Day. What you may not know, is that there was a third V weapon. 

The V-3 thankfully never got to the point of being used to its full extent, but it might have come pretty close. The massive gun that would have been the largest ever constructed was designed to hurl shells 165km (102 miles) at a rate of 600 per minute. This beast would have been able to repeatedly hit London from its bunkers around Calais. Allied aerial bombardment meant the V-3s in Northern France never became operational and a smaller version was instead directed against Luxembourg, with only minimal results. 

It was designed to be the largest gun the world had ever seen – and it very nearly was. 

The V Weapons 

The Vergeltungswaffen weapons, which translates into English as reprisal or retribution weapons – ominous I know, but this was the Nazis after all – began hitting mainland Britain in 1944. The V-1, a rudimentary flying bomb first landed on the English capital early in the morning of 13th June 1944. The British soon became quite adept at bringing them down but they still caused 6,184 civilian deaths in London. 

V-2 missile
V2 Missile

The V-2 was a more advanced and successful weapon. These rockets, which can be seen as an early precursor to our modern intercontinental ballistic missiles, were first launched against London from the Hague in Holland on 8th September 1944. Efforts to bring down the V-2s proved much harder than the V-1s, while allied air attacks against the launch sites were also largely ineffective. The V-2 attacks on Britain continued until the end of March 1944, before being turned on Belgium as the allied invasion force pushed forward. Interestingly, V-2 rockets were even deployed against German targets after Hitler ordered them used to destroy bridgeheads across the Rhine on 17th March 1945. 

The V-2 caused more damage than the V-1 but in total inflicted fewer deaths, with 2,754 killed in London as a result of the attacks. But the combined damage of the two weapons was horrific, with an estimated 20,000 houses damaged each day at the height of the bombing campaign. But it’s long been said that these V weapons were more psychological than physical. While their damage can’t be discounted, it was significantly less than what occurred during the Blitz. Things would have been quite different however if the third V weapon had ever been fully utilized. 

The V 3

Our knowledge and understanding of this weapon are unfortunately quite vague because they were either destroyed or withdrawn during the war. We are left with some intriguing black and white photos, patches of information and plenty of questions. 

But let’s begin with what we know – or rather what we think we know. The V 3 was quite unlike any gun before or after it, in that it used multiple propellant charges to generate its massive firepower. These charges were placed along the barrel and were designed to go off at the very moment the projectile passed. If that sounds horribly complicated, it really is and was one of the biggest obstacles to the V3’s success.   

The gun used solid-fuel rocket boosters instead of traditional explosives because they were easier to use and better suited to the gun’s unique requirements. These boosters were placed in symmetrical pairs, 32 in total we believe, along the barrel that was reported to be a huge 130 metres (430 ft) long. They were angled in such a way that their thrust would hit the base of the shell as it passed.

The gun was designed to use 150 mm (5.9 inches) calibre shells, each weighing 140 kg (310 lbs) and I said earlier in the video, it was hoped the gun could fire at a rate of 600 shells per minute with a muzzle velocity of 1,500 metres per second (4,900 ft/s).  


The idea behind a superweapon of this magnitude wasn’t new. The Germans had famously used the Paris Gun to shell the French capital from a distance of 120 km (75 miles) during the First World War but this was a step further. By the way, we have covered the Paris Gun along with the V-1 already on Megaprojects so if you’re into German superweapons then look no further. 

The V3’s design had been around since the mid-19th Century originating in the United States. Prototypes were built and tested in 1860 and 1880, but neither proved successful mainly because the explosive charges fired too early and the team behind it eventually abandoned the idea. 

Shortly before the end of World War I the French began designing their own version of the weapon, almost certainly in response to the Paris Gun, but with the conclusion of the war, those plans were indefinitely shelved.

Fast forward 22 years, and with French resistance crumbling, the Germans pushed past what had been the front lines of the Great War and quickly took control of the country. Now, whoever had been responsible for those plans for the French gun from the First World War apparently didn’t do a great job at concealing them and they quickly fell into German hands. 

The plans attracted the attention of August Cönders, a German engineer who had developed the bunker-busting Röchling shell. His initial blueprint called for the charges to be electrically activated rather than using explosives and presented the grand plan of 50 such guns launching 3,000 rounds a day at London. I’m sure you don’t need me to tell you the kind of damage that sort of barrage inflicts on a city. 

Tests on a small prototype 20 mm (0.7-inch |) multi-chamber gun were encouraging and the idea found its way to Albert Speer, Minister of Armaments and War Production, who in turn pitched the idea to Adolf Hitler. And as you can imagine, he loved the idea of raining shells down on London from Calais. 

By the end of 1943, a full calibre prototype had been built in Germany, but it came with a catalogue of problems. The gun repeatedly failed to generate the kind of muzzle velocity that had been proposed and even designing the projectiles were proving to be a nightmare. A full-scale 150-metre (490 ft) barrel was constructed on the island of Wolin in the Baltic Sea in early 1944 as the Germans prepared to put the first V3 through rigorous large-scale testing. 


Testing was hampered because of the slow process of designing a new projectile for this superweapon. Six designs were initially deemed satisfactory, with these eventually whittled down to four by the end of May 1944. 

The major problem with the projectiles had been obturation, which is essentially barrel blockage. This appears to have been solved by placing a sealing piston between the projectile and the initial propellant charge. This stopped the flash from the charge jumping ahead of the shell and enabled the steady control of all of the charges which enabled the projectile to successfully exit the barrel. 

Testing on Wolin took place between 20th – 24th May 1944 with the gun reaching distances of up to 88 km (55 mi). On 4th July 1944, a major test got underway with the gun firing 8 shots in quick succession. One of the shells travelled 93 km (58 mi) but the gun itself grumbled under the pressure and burst after firing the 8th round. Otherwise, barrels existed so this wasn’t a complete disaster, but a major setback nonetheless. This was also the last piece of information we have on full-scale testing.  

The Mimoyecques Site

Throughout development and testing, the Germans had been searching for and then preparing the perfect launch site to attack London. The site they had chosen was Mimoyecques, an area 18 km (11 miles) southwest of Calais and 8km (5 miles) from the coast meaning it would be out of range of Royal Navy guns lurking in the English Channel. 

Codenamed Wiese (meadow) and Bauvorhaben 711 (Construction Project 711), work began in Mimoyecques to build the V3 launch site in September 1943. It was built using prisoners of war from the nearby concentration camps alongside the Organisation Todt, which was the civil and military engineering organisation in Nazi Germany.   

The Mimoyecques site was composed of two parallel facilities roughly 1,000 metres (3,300 ft) apart. Each came with five weapon chambers each 105 metres (344 ft) long and angled at 50 degrees. Each of these chambers was designed to hold five V 3s clustered together – which would have added up to the 50 guns originally proposed. The chambers exited the hillside through enormous concrete slabs 30 metres (98 ft) wide and 5.5 metres (18 ft) thick designed to protect the muzzles below. 

Roughly 20 metres (100ft) below ground lies a complex network of tunnels and underground ammunition storage galleries as well as support facilities for the estimated 1,000 soldiers from the Artillerie Abteilung 705 unit that would have manned these guns.     

What we see today isn’t quite as extensive as had been planned because after a series of failures during testing it was decided to scale back operations to 3 chambers in each section instead of 5, even though work had already begun on the other chambers.

The Mimoyecques site suffered heavy bombing almost as soon as the allies realised that something was being constructed. The V1 and V2s were already hitting Britain and most likely the allies believed this to be a launch site of the earlier V weapons. As far as we know, the allied forces didn’t know about the existence of the V3 until after the war. 

But they certainly poured plenty of explosives down on the area. Between November 1943 and August 1944, allied aircraft dropped 4,102 tons of bombs on Mimoyecques. While the nearby village was all but obliterated, the depth and enormous amount of concrete used meant that much of the site remained intact and only 11 people died during the bombing raids – a quite unbelievable fact considering the amount of firepower and amount of people working at the site.   

Operation Aphrodite

One of the most daring planned raids on Mimoyecques came under Operation Aphrodite, which included what can only be described as rudimentary forms of drones. Two separate attacks were launched against Mimoyecques, the second of which included a young Joseph Kennedy Jr, older brother to the future U.S President John F Kennedy. 

Operation Aphrodite turned out to be almost completely ineffective but does paint a fascinating picture as to the extent the allies were willing to go to attack these launch sites in northern France. The plan was simple, yet complex enough to never work properly. The idea was to take B-17 and B-24 bombers that were no longer fit for regular duty and load them with explosives. The aircraft would then take off as normal but when it reached an altitude of 600 m (2,000 ft) the crew would bail out leaving the aircraft under the control of another aircraft nearby using the Azon System, a radio control system originally designed to guide bombs to their targets. The bombers also had two television cameras fitted in the cockpit with a view of both the ground and the gauges in the aircraft, which was then beamed back to the ‘mothership’ as it was referred to. 

In theory, the mothership could take control of the giant flying bomb these aircraft had become and guide them towards their target where they would dive nose first and obliterate everything on the ground – and hopefully beneath it also. It was hoped these kinds of attacks could destroy the formidable underground bunkers the Nazis had built across northern France. 

However, the operation was nothing short of disastrous. Of the 14 missions flown under Operation Aphrodite between August 1944 and October 1944, not a single plane managed to hit its intended target. 

On 12th August 1944, Lieutenant Joseph P. Kennedy, Jr. and Lieutenant Wilford J. Willy climbed into their B-24 Liberator stuffed with 9,071 kg (20,000 lbs) of explosives. The bomber hurtled along the runway at RAF Woodbridge before lifting slowly into the sky. The target that day was the still mysterious Mimoyecques Site, although unbeknown to the Allies, the site had already been effectively abandoned after a series of heavy bombing raids. Sadly, still some way off their bailout point, the explosives onboard the B-24 detonated unexpectedly, killing the two-man crew instantly.    

A New Target

It’s not known exactly when the Mimoyecques Site was finally put out of action, but we believe sometime in early July 1944. The complex had of course never been finished, let alone come anywhere close to firing a V3. Hitler’s ambition of hitting London with his third revenge weapon now seemed highly unlikely, but he soon set his sights on a new target. 

The V3 project was eventually passed to the SS who commissioned the construction of two shorter V-3 guns approximately 50 metres (160 ft) long with 12 side-chambers. The guns were placed in a wooded area near Lampaden about 13 kilometres (8.1 mi) southeast of Trier in Germany. 

The barrels pointed at the city of Luxembourg, which had already been liberated, roughly 43 kilometres (27 mi) away. This was at a time when Hitler was preparing his final roll of the dice, the massive Ardennes counteroffensive, also known as the Battle of the Bulge, which he hoped would swing the tide of war back in his favour. 

On 30th December 1944, the V3s began firing for the first time. The projectiles had again been adapted and were now 95 kg (209 lb) shells carrying a 7–9 kg (15–20 lb) explosive charge, while the gun itself had a muzzle velocity of around 935 metres per second (3,070 ft/s). The second gun went into operation on 11th January 1945 and until 22nd February 1945, a total of 183 rounds were fired at Luxembourg, killing 10 and wounding 35. 

The Greatest Gun That Never Was

As German defensive positions began crumbling along the western front, the V3s were withdrawn. It seems as if there were plenty of discussions about relocating them to other areas, but nothing concrete ever came of it, not least because the German railway system now lay in absolute tatters. The small version of the V3 fired its final round on 22nd January 1945, with U.S troops now only 3 kilometres (1.9 mi) away.

There is still so much we don’t know about the V3. We’re still not sure whether the Germans felt confident enough after testing to install them at Mimoyecques. The complexities of the underground site seem to suggest a confidence that the V3 would eventually come through. However, considering the number of issues it experienced during testing it’s unclear how effective the large-scale V3 would have actually been. This was a weapon that was rushed from the very start. In reality, it probably needed years more development and testing before taking its place in northern France. But with the war swinging in the Allies favour, the Germans became increasingly desperate to gain an advantage. We may never know just how close the V3 came to being fully operational and it remains the greatest and largest gun that never was.

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