The horror and chaos of the first hours of D-Day have become part of Hollywood myth: landing craft and men fighting through mine-infested waters and up beaches strafed by enemy gunfire as they attempt to establish the vital beachhead.
Less familiar is the secret war behind Operation Overlord, a war so confidential that little was known about it for another 20 years. It was the boffins’ war, a tense battle of measure and countermeasure, fought on the leading edge of scientific knowledge and in which the Germans had set the pace of technological change that the British had to match or go under.
Before the war, science had been a piecemeal affair of academic research and private ventures. But for the two years Overlord was in preparation, the challenge of landing the largest armada ever with minimum losses provided an extraordinary focus for the scientists. They grew in importance, moving centre stage to shape the whole war strategy, placing them at the heart of power for the first time.
One of the first areas revolutionised was air defence. It had been the prime minister, Stanley Baldwin, who in 1932 summarised the prevailing fatalism: ”The bomber will always get through.”
The distinguished chemist Sir Henry Tizard was given the brief to do something about it. His committee on air defence was responsible for radar, operational by the start of the war. He fostered a fundamental change of attitude — war cannot be waged on ”gusts of emotion”. Every activity should be subjected to scientific analysis.
The Germans knew an invasion was imminent and Germany’s most successful military commander, Erwin Rommel, had been put in charge of constructing the Atlantic Wall and organising defences in France. If they were to pinpoint where and when the assault was coming, the Allies could be assured of a devastating reception.
To maintain uncertainty right up to the last minute, the Allies began one of their major deceptions, Operation Fortitude. The object was to persuade the enemy that the landings would be made on the Pas de Calais rather than Normandy.
First, they invented the radio traffic of an entire phantom army based in south-east England whose commander was the one the Germans feared most, General George S Patten. Then the radar scientists at the Telecommunications Research Establishment at Malvern joined in to give this army even more credibility.
The idea was the brainchild of Dr Robert Cockburn. As a first step he had all of the early warning radar stations along the northern French coast put out of action, except for a dozen in the Pas de Calais region. They were left to see what Cockburn wanted them to see — the radar shadow of an invasion fleet slowly advancing across the Channel. His basic tool was ”Window”, strips of aluminium foil of different lengths.
However, Window could be seen on radar as shadows travelling at the speed of the aircraft dropping it, eventually dispersing into the atmosphere.
To mimic the image of a slow-moving invasion fleet, Cockburn therefore had to engineer a way of producing a continuous cloud of Window travelling at a fraction of the speed of the aircraft dropping it. He employed two precision bomber squadrons including 617, the famous Dambusters. Flying by night, these two squadrons had to fly elliptical orbits of 13km by 3km in exactly seven minutes.
As they went, kept in precise formation by newly developed radar, they had to drop 12 bundles of Window every minute. After completing one ellipse they had to advance 1,6km out to sea and begin another one.
Below them was a real fleet: just 14 RAF Air Sea Rescue launches, each flying 9m naval barrage balloons enclosing large radar reflectors. These each picked up enemy radar signals, amplified and returned them as echoes equivalent to a 10 000-ton ship. Other bombers flew on to the French coast, dropping not only bombs but pyrotechnics to create the sound of a small arms battle on the ground.
Such was the Allies’ air supremacy that not one German night fighter ventured out to explore the phantom fleet. Their anti-submarine radar was so strong that no U-boat disturbed the real invasion as the 6 000 landing craft and support ships moved in towards the Normandy beaches. Once there, the landing craft disgorged still further fruits of the boffins’ labours. There were ”Hobart’s Funnies”, tanks designed at special request from Winston Churchill by General Sir Percy Hobart.
Some were modified to sweep mines, others to lay bridges, to launch mortars and as flame-throwers. Rising mysteriously out of the water beside them was another secret weapon, the DD tank, Shermans equipped with floats and propellers. Kilometres off the coast were the tugs bringing across the ”Phoenixes”, 150 of them. These were 65m-long concrete caissons that were to make up the two artificial Mulberry harbours.
As there were so many ways in which such an elaborate deception as Fortitude could have been uncovered by the Germans, it was extraordinary that the Allied command had so much faith in it. The answer lay in another piece of leading-edge technology, introduced only a week before.
It was in 1939 that the shabby, nail-bitten, eccentric Alan Turing had first developed his ”bombe” to decrypt mechanically the German Enigma codes. Ever since, Bletchley Park had kept up a continuous flow of decoded messages. At its peak, Bletchley was decoding 18 000 messages daily.
However, the Enigma codes were only used by the Germans up to a certain level of importance. Beyond that, communications were passed on using the more secure Fish machines, which resembled teleprinters and used the 32 teleprinter symbols. These codes were broken by hand and, while this was much too slow for operational use, it provided the key to electronically automating some of the process.
Post Office engineers with their experience in electronics were pressed into service. So began the development of Colossus, the first programmable computer, based on Turing’s statistical ideas, which came into service in December 1943. When, in March 1944, the Fish traffic increased dramatically in quantity, Bletchley placed orders for the Mk II with 2 400 electronic valves. It arrived on site on May 31 and was operational a few hours later.
When Dwight Eisenhower and the other senior Allied commanders met on June 4 to make their decision on whether to invade, they had before them the crucial information from Colossus. They knew that the German high command still had no notion about where or when the invasion would come but still believed that it was likely to travel by the shortest route to the Pas de Calais.
The computing prototype, its valves glowing dimly in the corner of a Bletchley hut, had given the commanders the confidence necessary to proceed with the greatest invasion in history.
Up to this time, looming over the Allied leaders was the possibility that the Germans could be producing a nuclear weapon. It was this fear that had prompted the early ground-breaking work by British scientists on the fission bomb and it was their oddly christened Maud Report (it had been named after the English nanny to the young son of the Danish physicist Niels Bohr) that had set the agenda for the United States-based Manhattan Project. By 1944 a British Mission was making major contributions to the work at the Project’s Los Alamos laboratory.
Travelling with the liberation forces into Paris at the end of August was a British-US mission determined to find out. As an indication of how little real knowledge they had, the mission leaders had speculated that the great bunkers the Germans had built on the French coast might contain weapons with nuclear warheads.
Over the next two months the mission followed up leads that, if anything, alarmed rather than reassured. The Germans had cornered major supplies of thorium and uranium, and even if they did not have a completed bomb, they could be intending to use the radioactive material as a chemical weapon. Only in November, when Strasbourg fell and a number of German scientists were captured, was it clear that their project had moved hardly at all since 1942.
Shortly afterwards the leader of the scientific mission, Sam Goudsmit, found himself discussing the future with one of his military colleagues.
”If the Germans don’t have the bomb then we don’t need to use ours,” Goudsmit said, voicing a view common among many of the scientists working on the bomb. ”You don’t know the people in Washington,” came the reply. ”If we have such a weapon then we’ll use it.”
In those early days, the scientists petitioned the president against using the atomic bomb against Japan. Their move was indeed blocked in Washington.
It was the shape of things to come. Only 15 years later those scientists who came of age so triumphantly in the battle against the Germans were to witness the commander who had led Operation Overlord despair at what their success had spawned.
In 1960 after eight years as president during which he had tried fruitlessly to curb the arms race, Eisenhower spoke to the nation of his fear of ”the unwarranted influence of the military-industrial complex” and of public policy becoming ”captive of a scientific-technological elite”. In the four decades since then, those fears have not diminished. — Â