This article was first published in the May 2018 edition of BBC History Magazine


An Arctic blizzard was knifing through the ravine, tearing at the spruce trees and flinging snow at the rocky outcrops. The Rjukan gorge was a forbidding place in the depths of winter – an impenetrable Norwegian wilderness of such desolation that few people, or even animals, ever ventured there. But on the night of 27 February 1943, 10 shadowy figures could be seen creeping through the deep snowdrifts at the bottom of the gorge. All 10 had spent months in training for an audacious act of sabotage, one so risky that they didn’t expect to come out of it alive.

Joachim Rønneberg and his team had been parachuted into Norway from England in order to attack the most important industrial plant in Nazi-occupied Europe. Norsk Hydro was producing deuterium oxide or ‘heavy water’, a vital component in making an atomic bomb. If Hitler was to be thwarted in his attempt to develop a nuclear weapon, then Norsk Hydro’s Vemork plant had to be destroyed. But there was one major hurdle to sabotaging the plant. It was perched atop a 700ft shaft of rock and the only access was via a narrow bridge that spanned the Rjukan gorge. This bridge was under constant guard by German sentries and was forbidden to everyone except authorised personnel.

The only other means of reaching the plant was to scale the precipitous sides of the gorge and force an entry into the rear of the factory. But this would require a multitude of specialist skills, including mountaineering, endurance, silent killing and sabotage.

“Set Europe ablaze”

In the autumn of 1942, 23-year-old Joachim Rønneberg and a small group of Norwegian patriots volunteered to attend a highly secretive school that would teach them all of these skills. STS 21 had been established in Scotland with the aim of teaching would-be saboteurs the dark tricks of guerrilla warfare.

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STS 21 was run by the Special Operations Executive (SOE), an undercover organisation established more than two years earlier on the orders of Winston Churchill. Its purpose was to “set Europe ablaze” by conducting daring coup-de-main operations behind enemy lines. The prime minister liked to joke that it was his Ministry of Ungentlemanly Warfare, but there was nothing amusing about its work. Murder, assassination and sabotage were its stock in trade.

As SOE expanded, so did the number of training schools. By 1942 there were scores of them scattered up and down the country, mostly based in requisitioned mansions. There were so many, indeed, that one Cockney employee joshed that SOE actually stood for Stately ’Omes of England.

Some of the schools specialised in explosives and destruction: at Brickendonbury Manor (Station 17) in Hertfordshire, for example, agents were taught how to blow up everything from trains to bridges. Other places taught agents how to live behind enemy lines for months on end. There were also schools dedicated to wireless communications, parachute training and sharpshooting.

But the most unusual establishment was STS 21, the school to which Joachim Rønneberg and his comrades were sent. It was based in Arisaig House, an austere Victorian mansion on a remote hunting estate in Scotland’s western Highlands. Arisaig had been requisitioned in the spring of 1941 and rapidly transformed into an elite paramilitary centre, one whose work was of such secrecy that the surrounding countryside was declared off-limits to the general public. Here, in this 200,000-acre no-go area, Joachim Rønneberg and his men were taught the necessary skills for attacking the Vemork heavy water plant, from knife-fighting and pistol shooting to sabotage and endurance.

Arisaig House was run by two extraordinary individuals, both of whom were specialists in the art of dirty warfare. Eric Sykes and William Fairbairn had first come to the attentions of the War Office in 1941, when they pitched up unannounced in Whitehall, having just arrived from the far east. Both were close to retirement age and both had come to offer their services in the fight against Nazi Germany.

Eric Sykes, was known to his friends as Bill, after Dickens’s famously shady character. He was stocky and middle aged, with pebble-glass spectacles and a dimpled smile: he looked as if he couldn’t hurt a fly. One acquaintance said he had the “manner and appearance of an elderly, amiable clergyman”.

But Sykes was neither amiable nor a clergyman. He was an expert in silent killing – chilling, ruthless and clinical – and a man whose every sentence was said to end in the words, “and then kick him in the testicles”.

He had previously lived in Shanghai, where he had worked as the representative of two American firearms companies, Colt and Remington. He was a crack shot, arguably the finest in the world, and his speciality was shooting from the hip. Joachim Rønneberg found him absolutely terrifying.

Sykes’s comrade-in-arms was William ‘Shanghai Buster’ Fairbairn. Also portly, and myopic to boot, he too had the air of a Church of England chaplain. Yet he was a chaplain whose sermons had a nasty sting in the tail. “Kill or be killed.” It was his catchphrase.

His friends knew him as Delicate Dan, but he referred to himself as Mister Murder-Made-Easy. He would smile benevolently as he taught his pupils “how to break a man’s neck or smash his spine across your knee”.

Fairbairn had previously worked for the municipal police in Shanghai, a city infamous for its drug runners and armed gangsters. His role had been to quell gang warfare, a task he set to with such relish that there were some who wondered if he wasn’t a gangster himself.

A lifetime of fighting had left its mark. He had a broken nose and a long scar that stretched from ear to chin. Yet most people were struck by “his flashing white teeth that no amount of punching had ever loosened”.

New recruits to Arisaig were given a typical Fairbairn welcome. “The fighting I’m going to show you is not a sport. It’s every time, and always, a fight to the death.”

A blade into flesh

Joachim Rønneberg and his men were toughened up with a gruelling regime of physical training that included endurance runs over empty moorland and hiking with heavy packs. One infamous exercise, dreamed up by Sykes, was an 8 mile run (with rucksack) from Arisaig to Meoble that included a punishing 1,800ft climb over the top of Sgean Mor. Joachim Rønneberg excelled himself on this run, shaving fully nine minutes off the previous record. Such physical prowess would stand him in good stead when it came to fleeing the Nazis.

Knife-fighting was also one of the special-ties of Arisaig: Fairbairn and Sykes had designed their own double-edged commando knife – an 8in blade with a ribbed centre. Fairbairn knew from experience that it was one thing to train on a straw-filled dummy, quite another to plunge a blade into flesh. “We’ve got to get you bloodied,” he would say with a devilish grin as he led the men to the local slaughterhouse. He would get the men to stab a recently killed animal “to get the feel of human flesh that was still quivering”.

Such unorthodox training appalled the old-school generals of the British Army, but Arisaig’s instructors had the constant support of Winston Churchill and they trained men for some of the most outlandish missions of the Second World War. Among those who passed through STS 21 were the Czech assassins who killed the Nazi grandee Reinhard Heydrich in Prague, and the British commandos who destroyed the dry dock at St Nazaire, on the west coast of France.

Joachim Rønneberg was shocked when he attended his first lesson at STS 21. “Having been a very, very quiet, innocent boy back in Norway, and never been in any fight at all, I felt: ‘What are you doing? And what are they doing to you?’” But the Arisaig course taught him everything he needed to know about endurance and silent killing. By the time that he and his men finished the curriculum, they were highly motivated and superbly fit.

They were next sent to Brickendonbury Manor in order to learn about sabotage and explosives. Here, in another vast country house, they were taught by George Rheam, an unsmiling genius with thatch-coloured hair and penetrating steel eyes. Rheam was an engineer by training: he firmly believed that saboteurs needed to have an intuitive understanding of the machines they were intending to destroy. To this end, he acquired industrial plant machinery, including turbines, electrical installations and generators. Each would-be saboteur was then taught the best way to destroy each machine.

George Rheam was never quick to dispense with praise, yet he found the Norwegian team to be true professionals. “Their demolition work is exceedingly good,” he said at the end of their time at Brickendonbury, “and their weapon training outstanding.” He believed that “they have every chance of carrying out the operation successfully”.

Rønneberg and his comrades were parachuted into Norway on 17 February 1943. An Arctic blizzard was screaming in from the north, reducing visibility to zero, but they successfully landed on the Hardanger plateau, an ice-bound wilderness close to the Norsk Hydro plant.

After 10 days of reconnaissance, Rønneberg decided that it was time to strike. That night, at 8pm, the men crept down through the gorge and began the climb up the vertiginous sides, hauling themselves up the sheer rock face by clutching at spruce branches. As they sought precarious footing on icy ledges of rock, Rønneberg gave silent thanks to his training at Arisaig. The climb, he later said, was “like a training exercise in Scotland”.

It took many hours to reach the top and it was not until 3am that Rønneberg ordered the advance to the rear gates of the factory. The saboteurs slithered forwards, unseen by anyone, and successfully cut the chains with bolt-cutters. They then split into two groups. Rønneberg’s sabotage party clambered into a narrow cable shaft that led through the bedrock into the deserted plant room of the factory. The other group crouched in the snow, watching the nearby guard-house, in which sentries could be seen warming themselves around a stove. They were prepared to kill the Germans with their bare hands, if that should prove necessary.

Rønneberg worked at high speed once inside the plant. In complete darkness, he strapped the explosive charges to the heavy water machinery and then triggered the timed detonators. Once this was done, his team made a hasty escape, rejoining their comrades outside and then fleeing into the night. As they made their way back down into the gorge, they heard the muffled sound of the explosives detonating inside the factory.

Some of the men were disappointed that the explosions were not more spectacular. “Was this what we had come over a thousand miles to do?” asked one. But that muffled bang was exactly what was intended. The shaped charges had been specially designed to explode silently into the machinery, causing catastrophic damage to the works.

The damage was indeed catastrophic. All 18 cylinders were destroyed, along with their contents of heavy water. It cascaded down into the drains and was lost forever. It was a disaster for Hitler’s atomic programme, one from which it would never recover.

A splendid coup

Just a day or two after the sabotage mission, the damage was inspected by General von Falkenhorst, the German commander of the occupying forces in Norway. When he saw the extent of the destruction, he couldn’t help but praise the chutzpah of the saboteurs. “The most splendid coup I have seen in this war,” he said. He heaped all the blame on the German sentries who had failed to detect the British-trained saboteurs.

As for Rønneberg and his men, their training at Arisaig was to guarantee their survival as they made their escape across the bleak, forbidding Hardanger plateau. Rønneberg led them across the snowbound border into neutral Sweden, from where they would eventually return to England.

When news of their mission reached London, there was widespread rejoicing among those involved in the planning. “A 100 per cent success,” said a gleeful Colin Gubbins, the head of the Special Operations Executive. He congratulated the saboteurs for their bravado, and then congratulated those who had trained them.

He knew that such a mission would not have been successful without the exhaustive training programme devised by his three geniuses of dirty warfare: Eric Sykes, William Fairbairn and George Rheam.

Giles Milton is a writer who specialises in history. His books include Churchill’s Ministry of Ungentlemanly Warfare (John Murray, 2017)


Television: For more on SOE, don’t miss the five-part series Churchill’s Secret Agents, which is airing now on BBC Two and available on iPlayer