Would you give up your comfy technical desk job to join a military raid into hostile territory? Would you jump at the chance to put your world-leading technical knowledge to use in the most extreme of circumstances, even if your own side was under orders to shoot you if you got captured?

This was the choice that Jack Nissenthall, a radar expert and RAF flight sergeant, faced 75 years ago. At the time, the Second World War in the West was at a relative stalemate. Nazi Germany had conquered most of the continent and, unable to overcome the RAF’s tenacious resistance and invade the British Isles, had turned its appetite for war and conquest east towards communist Russia.

The time had come for the Allies to strike back. Technology was playing an increasingly important role in the war; the RAF’s Chain Home radar networks were instrumental in defeating the German Luftwaffe in the Battle of Britain. Inspired by the RAF’s victory, and increasingly hurting from RAF and US bomber raids on its cities and military bases, the Germans started building a radar network of their own along France’s northern coast.

Aerial reconnaissance photos indicated that one of these new Freya radar sets had been installed at Pourville-sur-Mer, near Dieppe. A military raid on Dieppe, to test British and Canadian plans for an amphibious invasion, was already being planned. Senior officers immediately added a sub-plan to the Dieppe raid: a small force would be detached to attack the Pourville radar station. There, a radar expert would dismantle the station’s vital equipment and transport it back to the UK for analysis.

Nissenthall, a Jewish cockney who had a lifelong fascination with electronics and radio technology, had joined the Air Force as an apprentice in 1936. By the outbreak of the war in 1939 he was assigned to RAF radio direction finding stations (RDF, the short-lived original term for radar) and rapidly built up a reputation as a competent and technically skilled operator. Before the war he had also worked directly with Robert Watson-Watt, widely regarded today as the father of radar.

“... must under no circumstances fall into enemy hands”

Thanks to Nissenthall’s advanced knowledge of RAF radar systems, practices and weak spots, he was the ideal man to identify exactly what equipment should be taken from the Freya station at Pourville.

A self-taught technical expert with thorough knowledge of hands-on electronic engineering and system capabilities alike, Nissenthall’s young age (22), enthusiasm for military life (he had given up his leave voluntarily to undertake the gruelling Commando course in Scotland) and the fact he was unmarried made him the perfect candidate for the Dieppe raid.

Yet there was one snag. Precisely because of his advanced technical knowledge, the consequences for the Allied war effort if Nissenthall was captured would be disastrous. Hence it was ordered by Air Commodore Victor Tait, the RAF’s Director of Signals and Radar, that a special bodyguard would accompany Nissenthall. If it looked likely that he might be captured, Nissenthall was to be shot by his own side.

This was a carbon copy of an almost identical raid that took place six months previously against a different type of coastal radar station near the French village of Bruneval. There, the RAF radar expert, FS Charles Cox, also had a personal bodyguard under orders to ensure he was not captured. Commanders hoped they could repeat that operation's success.

The raid

More than 5,000 soldiers of the First Canadian Division set off from the south coast of England in the early hours of 19 August 1942. Embedded with A Company of the South Saskatchewan Regiment, Nissenthall’s 11-man bodyguard landed on French soil – but on the wrong side of the Scie River from the radar station.

After finding their way to their intended starting point, the team ran into stiff German resistance. Casualties soon mounted up as they probed the area, looking for a way into the radar station.

Thanks to the Bruneval raid six months previously, the Germans had beefed up their defences around coastal radar stations. This, combined with the naivete of the Allied planners back in Britain, had left the Canadians exposed and vulnerable. Though Nissenthall’s team had just about reached the radar station, there was no hope they would be able to get inside it, much less examine it, dismantle it and take away the most valuable parts of the Freya set inside.

While the team racked their brains to figure out a way into the station, Nissenthall observed the Freya’s antenna. As it moved in a 180-degree arc, he noted that it rotated and paused – revealing that it was a precision set capable of focusing on individual targets, such as formations of Allied bombers.

Then Nissenthall had a brainwave. As he ranged around the rear of the radar station he caught sight of a telegraph pole with cables leading into its buildings. In the very early stages of the war the RAF had been able to eavesdrop on German units across the Channel by listening in on their radio chatter. As time went on, the Germans got round to building permanent military telephone networks – and the airwaves fell silent, depriving British intelligence of their primary source.

If, reasoned Nissenthall, the telephone lines were cut, the station’s operators would be forced to switch to radio – once again allowing British signals intelligence experts to listen in and figure out the set’s range, precision and the number of contacts it could track at once.

So, with bullets cracking past in both directions, Nissenthall shimmied up the telegraph pole and cut each cable, one by one, expecting at any moment to get shot. Sure enough, once the phone lines were down, the Germans switched to radio for passing vital messages about the air battle raging far above them.

Listening in

Nissenthall and just one of his original bodyguard made it back to England alive, aboard Royal Navy landing craft. This mirrored the wider tactical picture: around two thirds of the casualties were Canadians, either being killed, injured or taken prisoner.

Yet it worked. The information Nissenthall was able to give intelligence officers based on a close-up look at the radar aerial (there were no precision satellite images in those days; photo reconnaissance was generally carried out by modified Spitfires making low-level passes with sideways-facing cameras) enabled them to, along with the radio traffic they had intercepted, form an accurate picture of the Freya set’s capabilities. This in turn informed RAF strategy for everything from massed night bomber raids to radar-jamming technology.

The Dieppe raid, formally known as Operation Jubilee, laid the foundations for the Allied invasion of Axis-occupied North Africa and later Operation Overlord, the D-Day landings. Field Marshal Lord Louis Mountbatten later commented that each Canadian who died on the beaches of Dieppe saved ten men’s lives during D-Day. Operational planners looked at the bloody, tactical disaster that had been Dieppe and remorselessly dissected it, hammering home each and every lesson that could be extracted.

Two years later the Allied invasion of occupied Europe went almost as smoothly as had been hoped for. A year after that, the Second World War in Europe came to an end.

In spite of his heroism, Nissenthall was never given any official recognition for his part in the raid. None of the Canadians knew who he really was until 25 years later, when he turned up at a regimental reunion out of the blue. As far as the RAF was concerned, Nissenthall (who later changed his surname to Nissen) was on a routine short-term posting. Even FS Cox, who had played a very similar part in the earlier Bruneval radar station raid, received the Military Medal.

But the heroism of one electronics genius contributed in a significant way to the neutralising of Nazi Germany’s technical superiority, and eventually to the destruction of that evil regime. Nissenthall himself acknowledged the risks of being identified as a Jew – and dismissed them, refusing offers from senior officers to have his identity discs re-issued to identify him as a Roman Catholic or some other faith that would draw less attention from his captors if he was caught. (Those officers had no idea about the secret orders to kill him rather than let him be captured.)

One techie helped change the course of the war that day, 75 years ago. ®

Further reading

Green Beach, James Leasor – a full-length novel-style retelling about the Pourville raid, drawing heavily on interviews with Nissenthall and the survivors of A Company.

BBC WW2 People’s War – a rendering down of Green Beach to its essential facts, along with some post-war detail that was not available to Leasor.

Operation Biting – a broad overview of the Bruneval raid which took place six months before Nissenthall’s daring exploits at Pourville.

Historynet’s detailed account of the Pourville raid, as originally published in World War II magazine in 1998. This, too, draws heavily on Green Beach.