The plan was for this audacious raid to be carried out by ‘C’ Company of the 2nd Battalion, 1st Parachute Brigade commanded by Major John Frost. Their specialist would be radar operator Flight-Sergeant C. W. H. Cox. None of the men was told anything about the raid until the last minute, and training went on with scale models of the enemy terrain and with trials on the beaches of southern England.
On the night of 27 February 1942 the teams were dropped by parachute from Whitley aircraft flying at just 600ft (180m). The beach was secured, and teams rushed to the villa where they found a single German soldier guarding the equipment. German troops from a nearby pillbox were firing into the site as the British troops disassembled the Würzburg radar aerial, removing the important components which were all packed and taken quickly to the beach. There were problems making radio contact with the Navy, who were supposed to be ready to collect the men and their spoils, but had encountered a German warship and had to take evasive action. The German pillbox had been silenced and red flares were shot into the sky — at which point the Navy appeared in rough seas to retrieve the teams. Under enemy fire six landing craft arrived to collect their precious cargo. The ship was escorted back to Portsmouth Harbour by Royal Navy destroyers with RAF Spitfires flying overhead; the patriotic song Rule Britannia was played at high volume from loudspeakers. The raid was entirely successful. The airborne troops suffered only a few casualties, and the pieces of the radar they brought back, along with a German radar technician, allowed British scientists to understand German advances in radar and to create counter-measures to neutralize those advances.
Brave members of the French resistance continued to supply information to Britain and it was soon discovered that all German radar stations operated on a small number of frequencies, and they could easily be jammed. When a huge and devastating Allied bombing raid on Hamburg was planned for July 1943, fragments of metallic strips were dropped — once again, exactly one-quarter as long as the wavelength of the German radar beams, to maximize reflections — and the signals from the radar stations were completely obliterated. This chaff was known as ‘window’ by the Royal Air Force and had been independently discovered in Germany, where it was known as Düppel. It is a sign of the confused strategic planning by the Nazis that, having pioneered the use of reflecting chaff, the Germans did nothing to prepare themselves for its use by the Allies.
The Germans lacked the ability and knowledge to manufacture radar systems in which the radio beams could be tuned to a desired frequency, and this capability gave the British superiority in this vital area of defensive warfare. The early radar trials in Britain used a frequency of about 10MHz and the Chain Home stations began at 20MHz and later extended their range up to 70MHz — but the tracking radars operated at 200–800MHz. In 1940 the Americans began to use a cavity magnetron transmitter which went from the megahertz range up to gigahertz frequencies. It was small enough to fit into aircraft, and the H2S radar which was used by United States Air Force bombers had a frequency of 3GHz. It could show the details of the ground beneath the aircraft with unprecedented accuracy — but it was decided never to use it over Germany. Allied intelligence had reported that the Germans believed 800MHz was the highest frequency that radar could use, and it was feared that — if an American plane was shot down, and the secret of its radar was discovered by the Germans — the balance of power could radically change.
In the event, this proved to be a groundless fear. In the spring of 1943 an American bomber was brought down near Rotterdam, Netherlands, and the onboard H2S radar and the intact magnetron fell into German hands. They set out at once to reconstruct their own version, code named Rotterdamgerät, but the first examples were manufactured only when the war was nearing its end.
Installations of British radar detectors on Royal Navy ships allowed them easily to detect German submarines on the surface of the sea, and so the Germans worked on methods of preventing their U-boats from generating an echo, so they could thus escape detection. They soon found that a mixture of rubber and carbon painted onto a submarine’s superstructure greatly diminished the strength of its radar signature, and they tested it in a dry dock until they had perfected the ideal recipe. Surprisingly, the British warships continued to detect the submarines as though nothing had happened. The reason was simple — when wet with seawater, the protective layer no longer worked and radar detection could function as normal.
We must not dismiss the German idea out of hand, however: this was the origin of what we now know as ‘stealth technology’. Once again, a development from World War II underpins a crucial aspect of present-day warfare.
Radar in Britain had a decisive effect on the conduct and duration of the war. Following enemy aircraft and ships that were otherwise invisible was of crucial importance. The Chain Home network was even shown to be able to detect V-2 rockets long before they reached the British coast and, although nothing could be done to prevent their arrival, this is historically significant as the first ballistic missile radar detection system in the world. These systems are now everywhere. It is also important to note that Hungarian scientists used their own radar to bounce signals off the moon in 1944. This was the first time it was ever achieved, and they accurately measured the distance of the moon from the earth for the first time in history.
Radar was firmly established and had become refined by the end of World War II. During the Vietnam War of 1955–75, anti-radiation missiles were developed which would home onto the beam emitted by a radar transmitter and destroy the installation, thus using the radar against itself. As devices became increasingly compact, radar speed detectors entered service with the police force. And so we can look back at the stimulus that World War II gave to the development of radar — and can bear in mind that the same principle had been used to detect shipping before World War I began. Radar has enjoyed a lengthy history. It can now entrap you on a highway, it is an integral part of global transportation, and it promises to have an illustrious future.
Harnessing reflections of radio waves bounced back from aircraft and ships was the principle behind radar — but great effort also went into using radio beams themselves as an aid to navigation. This was born in 1932 as an aircraft landing system developed by the German company Lorentz AG, and was the brainchild of Dr E. Kramar. Like all good ideas, it was rooted in simplicity and was a brilliant innovation. It worked by having three radio masts that were transmitting 38MHz signals towards an approaching plane from the end of the runway. The antenna in the middle sent a single, continuous signal; the others (to the left and right) turned on and off alternately. The antenna to the left sent dashes each lasting ⅛th second, whereas the right antenna sent alternate dashes each ⅞th second long. The pilot of an approaching aircraft that was exactly on the correct, central flight path would tune to the radio signal and hear a continuous tone. If the plane was too far to the left, dashes would be heard; if it was over to the right then the short dots would be received. It was the first successful remote landing system and within two years it had been installed by Lufthansa on their aircraft, and was widely sold around the world. It was ahead of its time, and worked reliably over a distance up to about 30 miles (50km). As the Luftwaffe expanded, they experimented with a range of alternative solutions to the same problem. The British, meanwhile, trained their pilots in celestial navigation to aid flying at night; the Luftwaffe ignored something so old-fashioned, concentrating on wireless systems instead.