Radar Saves The Day

AT ABOUT 10:30 ON AN otherwise uneventful morning, August 15, 1940, radar operators sitting in the cramped wooden huts studded every 20 miles along the southern and eastern coasts of England were startled to see their electronic equipment suddenly go haywire. Above each but loomed a skeletal pair of 300-foot steel towers with several transmitting antennae strung between them, accompanied by a second set, of wood measuring about 200 feet, that bore a series of crossed receiving antennae.

Nobody but these handpicked technicians knew the purpose of these strange-looking masts -yet this top-secret project would determine whether Britain could continue to fight Nazi Germany. Since the outbreak of war in September 1939, Britain had suffered an ignominious series of losses: Poland and the Low Countries were gone, France too, and whatever remained of the British army had been salvaged from Dunkirk by mere good fortune. Beginning in early July, when Hitler authorized the conquest of Britain, waves of German Heinkel He 111, Junkers Ju 87 and 88, and Dornier Do 17 bombers had attempted to draw the Royal Air Force-the major obstacle preventing a seaborne invasion-into an aerial battle of annihilation. So far, the defenses had held, but the RAF's pool of fighters had fallen perilously low. The radar operators, most of them women (female voices carried the most clearly over radio), stared at their cathode-ray- tube oscilloscopes, which resembled small, primitive television sets. It was largely unproven technology, and there remained gremlins aplenty to play tricks on the unwary. The crazy electronic blur puzzling the operators on August 15 could simply be yet another annoying malfunction . . . or it might mean their sensors were being swamped by a torrent of echoes indicating an unprecedentedly large German bomber armada. By lunchtime, it was alarmingly apparent that hundreds upon hundreds of aircraft were swarming across the English Channel-from every direction, their targets unknown.

By then the radar operators had erred on the side of caution and passed on their signals to the filter room at Fighter Command headquarters. There the various plottings were cross-referenced for accuracy before being sent to the operations room, where a gigantic map of Great Britain, divided into grids, was laid out on a table. As the details of a raid's altitude, position, target, status, and bearing firmed up, women pushed colored markers back and forth across the map. As the strategic picture clarified, the data were then distributed to the relevant group and sector controllers, who scrambled their Spitfires and Hurricanes to intercept the enemy.

August 15 would prove to be one of the most decisive actions of the Battle of Britain, a day that Prime Minister Winston Churchill would soon call "one of the greatest . . in history."

While courage was never lacking among its pilots and ground staff, the Royal Air Force's eventual victory- and the country's consequent escape from German occupation- hinged on the aggressive and innovative use of radar, a new and unproven technology. No other nation had recognized radar's immense possibilities during the interwar years and worked to develop it. The United Kingdom succeeded where all others had failed by dint of its unique strategic and historical circumstances, as well as the efforts of a few remarkable individuals. There was nothing inevitable about the British triumph, and matters would have turned out quite differently had it not been for the secret weapon that stopped Hitler in his tracks.

IT IS A STORY FAMILIAR to many, but not so well known is that critical elements of the 1940 Battle of Britain were set in motion on Christmas Eve 1914, six months after the outbreak of the First World War. On that evening, a solitary German aircraft had appeared off the English coast, dropped a number of bombs into the sea, and returned home.

From then on and until three months before the armistice of November 11, 1918, the Germans con- ducted bombing campaigns by airplanes, which would kill 619 Britons and injure 1,650 more, and Zeppelins, which left another 498 dead and 1,236 wounded. For the British, it was a terrifying introduction to a deadly new world of aerial warfare-the Wright Brothers had first achieved powered flight little more than a decade before. The German attacks heralded an age of brutish civilian slaughter, of dread at what might lurk above.

The British authorities initially deployed an antiaircraft artillery perimeter within a six-mile radius of London's Charing Cross -the center of the city- and dispatched fighter squadrons as soon as bombers were seen. But by the fall of 1915, it was clear that nothing was effective against the raiders. Indeed, the fighters, noted the director of the Air Department gloomily, were only useful to oy the spirits of the worried population watching from below.

Unlike naval and army equipment, which moved atop essentially flat surfaces and along generally predictable paths such as roads or sea- lanes, aircraft operated in the immense cubic dimensions of airspace. Pilots could quickly alter their bearing, speed, and altitude; their crafts' relatively tiny size made them difficult to pinpoint against the vast backdrop of the sky at anything other than short range-and that was before cloud cover was taken into account.

Innovations in engine design, along with the development of lighter and stronger materials, enabled bombers to fly ever faster, farther, and higher, increasing their relative advantage over fighters. In 1932, for instance, the Air Staff estimated that, after crossing the southern coast, an enemy fleet, flying between 150 to 200 miles per hour, would be bombing St. Paul's Cathedral and Buckingham Palace within 20 to 25 minutes. Fighters required at least seven minutes to scramble even when at "ready" status and another 10 to gain the requisite altitude, leaving little time for the defenders to bring the raiders down over open country-even assuming they were intercepted in the first place. By 1937 the Heinkel He 111 cruised at 214 miles per hour - thereby placing still greater pressure on the fighters.

Of course, once fighters did engage bombers, the latter came off worse. Given their distance from home, severely damaged German bombers could be written off and their parachuting pilots taken prisoner. The British understood that the trick to achieving air superiority was to ensure that their fighters could be scrambled to the right height at the right time, along the right vector. To better their chances of interception, the Royal Air Force needed to stretch the increasingly limited warning time.

Such thinking led the British to focus on the twin objectives of "seeing" farther into the blue and harrying the Germans relentlessly once they crossed into British airspace. The power to detect bombers as they passed over the French rather than the British coastline would gain the defenders precious minutes. The longer the fighters could engage the bombers, the better they could press their advantage and let attrition play its role.

On July 17, 1917, Brig. Gen. Edward "Splash" Ashmore, an Old Etonian artilleryman seemingly the epitome of the stern Edwardian soldier, had taken command of the newly created London Air Defense Area. But despite outward appearances, Ashmore was a forward-looking officer. Transferring to the nascent Royal Flying Corps was a significant career risk, but he rose to the task and fully committed to an air defense system that was constructed along the most modern lines.

He promoted newfangled "acoustic locators" capable of magnifying sound. While not markedly increasing the range at which bombers could be detected, these large conical horns, often operated by blind men with acute hearing, did help to take accurate bearings on the intruders. He also quickly integrated newly invented techniques of gauging altitude and improving gun control.

In addition, Ashmore amalgamated the existing hodgepodge of observer posts, searchlight stations, fighter bases, balloon aprons, and antiaircraft guns into an interconnected system coordinated from an operations room in London. "Stretched far across one side of a wall was a vast map of England marked in squares, each square an area plentifully numbered," remembered one visitor. "As the air raiders winged from the coast, the areas of the boundaries they crossed were illuminated on the map. Little ominous lights crept nearer and nearer to London. Round the room were groups of telephones, with expectant figures with headphones glued to their ears, in immediate touch with every searchlight crew, every gun emplacement, and every aerodrome round London up from the sea. The General [Ashmore] sat in a gallery, overlooking the map, alert and grim. Incoming messages were incessantly put in front of him. Every station, searchlight, aerodrome, balloon- apron, emergency landing post, coastal and inland watching post was connected by telephone to a sub- control. These twenty- five sub-controls were connected to the little room which was reputed to be bomb-proof.... The illuminated counters crossed the map. As they passed, we followed the course of all aircraft flying over the country-from the moment when an observer . . . saw a machine overhead, to the time when the counter representing it appeared on the map in our cosy nest. Flicking a switch, the General could talk to any commander in the area-at a flick this squadron would take off."

Ashmore's system worked wonders. His telephonists could process 55 messages an hour. Only 30 seconds elapsed between an observer's spotting an aircraft and a counter's appearance on the map board. On May 19, 1918, the air defense system worked spectacularly well against the largest raid of the war, a 43-aircraft blitz on London. Only 13 bombers reached their objective and safely returned home; the rest either turned back or were shot down.

The victory, however, thinly concealed the sheer effort devoted to the defense. On that night, 84 fighters took to the air and 126 guns fired more than 30,000 rounds. To counter the entire bombing offensive, the British had been forced to allocate no fewer than 469 anti-aircraft guns, 622 searchlights, 258 height finders, and 10 acoustic locators, manned full- time by 6,136 officers and crew. The locators had proved useful, but little practical progress had been made toward extending their range of detection. This was not for want of trying: apart from amplifying sound, however, there seemed to be no way of extending the visual or auditory perimeter.

Still, by the end of the war, the British understood that an effective national air defense system stood on four interdependent pillars: effective long- range detection; joining battle in the skies at home; excellent communications and centralized command control; and meticulous plotting and continuous tracking of the raiders' positions, speed, and bearings. With this knowledge, the British had achieved a conceptual revolution in a few short years.

As any inventor will attest, bringing an idea from concept into reality remains difficult at best-and in this respect Britain's postwar air planners and the public cannot be blamed for thinking that air defense was a pipe dream. The gaping and evidently growing imbalance between offensive power and defensive abilities demonstrated only too well that future bombers would overwhelm any obstacle created to block them. For most Britons between the two world wars, there seemed only two answers to this quandary. The first, popular with a public appalled by the horrific slaughter of trench warfare, was abolishing war itself. Outlawing bombers would mark the first step toward that objective. In hindsight, such lofty aims seem quaint, but it is difficult to overestimate the attraction of pacifism during those years, especially in Britain.

The World Disarmament Conference of 1932-34 tried to do just that, gamely attempting to ban submarines, military aircraft, and artillery. In Britain, defeat stalked any parliamentary candidate who did not espouse disarmament; only brave (or fool hardy) politicians openly supported strengthening Britain's forces. Ten million Britons declared in the national Peace Ballot referendum of June 1935 that they desired "an all-round abolition of national military and naval aircraft." As late as December 1937 -just two years before the outbreak of World War II- a large poll found that half its respondents still favored a general reduction of all armaments.

More than anything, the public feared unstoppable waves of bombers that would rain destruction on their heads. According to the military theorist Colonel J. F. C. Fuller, "A fleet of 500 aeroplanes, each carrying 500 ten-pound bombs . . . might cause 200,000 minor casualties and throw [London] into panic within half an hour of their arrival. Picture, if you can, what the result will be: London for several days will be one vast raving Bedlam, the hospitals will be less will shriek for help, the city will be a pandemonium." That the next war would end civilization within days became a common trope of the era, reinforced by movies, newspapers, and books. The citizenry of the 1930s envisaged, in short, a European war in the same apocalyptic manner as those of the cold war did a global thermonuclear holocaust.

Those reluctant to buy into such dire predictions proposed that British air strategy should be based on deterrence, not disarmament. In-stead of reducing the number of bombers to zero, the bomber fleet should be ramped up enough to threaten a devastating retaliatory strike on Berlin. In November 1932 Stanley Baldwin, the de facto prime minister of the coalition government, grimly commented that because "the bomber will always get through," then the "only defense is in offense, which means that you have got to kill more women and children more quickly than the enemy if you want to save yourselves." By March 1934 the Disarmament Conference had collapsed, and Baldwin committed Britain to building a bomber force numerically equal to that of "any country within striking distance of our shores."

What deterrence and disarmament had in common was their reluctance to credit any kind of defense against the bomber. Not everyone agreed with this pessimistic appraisal. A contrarian cadre lurked within the British military and political establishment that drew succor from the success of Ashmore's World War I system. Despite being almost forgotten amid the attention devoted to the bomber, that system continued to be refined quietly and on a bare-bones budget-throughout the 1920s and early 1930s.

In 1924 Ashmore had founded the supersecret Royal Observer Corps, whose task it was to spot aircraft. Its advent ensured that a comprehensive network of observer posts remained intact throughout the country. Likewise, a number of obscure subcommittees within the Air Ministry were making sure that not only the observers but also fighter headquarters, gun stations, searchlight batteries, and sector commands were telephonically linked. Meanwhile, the Air Defense Experimental Establishment at Biggin Hill furtively experimented with acoustic detection by building "sound mirrors," curved concrete walls ranging from 20 feet to 200 feet long that concentrated the echoes of approaching aircraft. A 1932 test demonstrated that an unaided ear could hear aircraft 6.5 miles away, while the 200-foot mirror helped technicians detect them at up to 20 miles.

Since the early 1920s, the proponents of defensive technology measures had found a friend in Baldwin. A powerful and popular, if enigmatic, figure in politics for decades - a kind of British FDR, and just as canny-only Baldwin had the weight to keep this back door secretly open, even at the height of the peace movement. In July 1934 he went so far as to subtly revise his November 1932 view-that the "bomber will always get through" - by adding it was wrong to assume that "it is [a] waste of money to increase your [defending] air force. . . . Some will always get through; but there comes a point when [the enemy] has to think very seriously whether the game is worth the candle."

The Commons paid little attention to Baldwin's remark. Not so the contrarians, who redoubled their efforts to force the Germans to rethink how much that candle of theirs was worth. Chief among them was H. E. Wimperis, the Air Ministry's director of scientific research, who that October asked Henry Tizard, a respected scientist chairing the Aeronautical Research Committee, what he thought of the matter. Tizard, once described as resembling a "highly intelligent and sensitive frog," and whose credo was that in science one must "ask the right question, and it is the choice of problem more than anything else that marks the man of genius," said bluntly that he thought acoustic methods were likely to be a technological dead end, thanks to advances in muffling the sounds of engines and propellers. But he agreed that he would "let you know [his final opinion] after I have made some enquiries." A few weeks later Wimperis noted that Tizard was investigating the "prospect of defence methods at last overtaking those of the attack." The "method" that Wimperis referenced was the detection and tracking of aircraft by means of radar-then being worked on by Robert Watson- Watt, a jovial Scottish radio expert at the National Physical Laboratory.

Scientists had known the basic principles of radar for more than a half century: when radio waves encountered a metallic object, they would bounce off it and return to the point of transmission. The time it took for the echo to be received indicated that object's distance. In 1888 the German physicist Heinrich Hertz had demonstrated that radio waves were reflective but concluded that "it's of no use whatsoever." In 1904 the German engineer Christian Hiilsmeyer had disagreed and patented a simple device that in theory could detect a fog-shrouded vessel within a mile or two. Unfortunately for Hiilsmeyer, the German navy sided with Hertz and dismissed his "telemobiloscope" as pointless. In 1917 the brilliant mechanical and electrical engineer Nikola Tesla had speculated that, by transmitting electromagnetic waves, "we may determine the relative position or course of a moving object, such as a vessel at sea, the distance traversed by the same, or its speed." Five years later, the Italian radio pioneer Guglielmo Marconi, addressing an audience of radio engineers on naval detection, had said substantially the same thing.

Encouraged by these titans, scientists around the world conducted experiments -for naval purposes -but little came of them. Then in January 1931 a team of British Post Office engineers noticed that their shortwave radio receiver had accidentally picked up reflections from an overhead aircraft. No one paid attention to this singular phenomenon, mostly because it was a case of wave interference, which could not be used to determine altitude or speed. In November 1934 an American team patented a "system for detecting objects by radio," but the project died when the U.S. Navy proved wholly uninterested. As a matter of course, the military attaches of Germany, France, and the Soviet Union forwarded copies of the patent to their governments, but various efforts to make something useful out of it came to naught. (The French did succeed in placing a rudimentary radar set, based on Tesla's principles, in the SS Normandie for the detection of icebergs.)

At the time, Watson-Watt had been investigating the practicality of creating a "death ray," a weapon that would concentrate radio beams at a pilot in flight. Watson-Watt concluded that the tremendous amount of energy necessary to incapacitate a human being simply could not be achieved. With Tizard's inquiry, however, his mind began turning toward "the still difficult but less unpromising problem of radio-detection as opposed to radio-destruction." During the First World War Watson-Watt had worked at the Metereological Office trying to detect thunderstorms by radio impulses, and in 1922 he had even built an accurate, if low-sensitivity, direction finder.

On February 12, 1935, Watson-Watt submitted a memorandum, "Detection of Aircraft by Radio Methods," laying out his thoughts for Tizard and Wimpenis. He was confident that the nuts-and-bolts hardware -wideband amplifiers, pulse circuits, high-frequency transmitters, cathode-ray- display tubes, and the like-was now sufficiently advanced to make a breakthrough possible. The Scot also had in mind a ready-made technique developed in the 1920s by his colleague Edward Appleton for atmospheric measurements, to receive the reflected signals on a "cathode-ray oscilloscope directly calibrated with a linear distance scale." If a large number of pulses a second were sent, "by superposition of the successive images on a synchronized time base a very easily visible sustained image permitting close measurement and even showing the advance of the craft" could be attained. Previously indecipherable data could be thus graphically depicted and then tracked. Significantly, Watson-Watt's use of pulses, by which the transmitter would fire a beat lasting a few millionths of a second along a concentrated directional beam to achieve greater accuracy, distinguished the British effort from its predecessors. In so doing, Watson-Watt had introduced a critical refinement to a generally known principle-but in such small details are great inventions made.

Tizard took news of the development to Air Marshal Sir Hugh Dowding, the head of RAF Fighter Command, for whom on February 26 Watson-Watt replicated the 1931 Post Office result in a field near Daventry, 75 miles north of London. After the demonstration, the dazzled Sir Hugh (known within the ranks as "Stuffy") told Watson-Watt that he could have "all the money" he wanted ("within reason," he cautiously added). Soon afterward, Dowding reported the results to Lord Londonderry, the Secretary of State for Air, who in turn informed Baldwin on March 14, 1935, that "our potential capacity to defend this country against air attack has been materially increased by the work of the last fortnight." With that, radar was well on its way to becoming Fighter Command's official alternative to the bomber deterrent and the anointed successor to the acoustic method.

Only the British had discerned radar's hidden potential and identified it from the beginning as the possible centerpiece of a national air defense system. A device that could be slotted within an existing framework, it was the missing link that fulfilled the 20- year quest to peer far beyond the coastline. All told, radar was a contextual technology, emerging in Britain as a critical new development owing to a constellation of fortuitous factors while in other countries it remained little more than an iceberg-detecting gadget.

For that reason, the British used radar to enhance aircraft detection while other nations, such as the United States, focused on detecting ships. Thus, in the late 1930s the Germans also had a radar unit, code-named Freya, which worked well but could not measure height. Why? Evidently the Germans did not need such information because the Luftwaffe was designed as an exclusively offensive force. In August 1939, when the Graf Zeppelin airship overflew a radar antenna on an espionage mission, the Nazis still assumed that the British thought the same way. Their intelligence analysts casually wrote the device off as a shipping detector.

The World War I success of sonar, a technology that uses sound to echolocate bodies in the water, had blinded Berlin to the possibilities of radar. During that war the powerful British Royal Navy had developed the ability to hunt German U-boats acoustically. After the armistice it had continued to develop the technology.

In the 1930s the Americans, interested in a mightier navy, and the Germans, who wanted more effective submarines, were naturally interested only in how radar could be used as an advanced form of sonar. What they did not know was that the British had already turned their attention skyward.

British scientists would spend years fine-tuning the technology, vastly improving range, accuracy, and the ability to calculate aircraft bearing, altitude, and speed. Progress was amazingly rapid. As early as June 1935, Watson-Watt was detecting targets nearly 17 miles away; by the end of the year, the range had increased to 60 miles. By September his superiors had already approved the "institution of a chain of radio detection stations," as well as the purchase of Bawdsey Manor in eastern England to provide the radar teams with a secure site for conducting experiments. That year, tactical weekly exercises using the new equipment took place in Ashmore's reactivated operations room; the following July, a new facility was built along the same lines.

Lord Londonderry gained Baldwin's approval to build prototypes of two advanced fighters that could complement the radar system- the immortal Spitfire and the legendary Hurricane. In 1937 the first radar station was built, operating at a high frequency of 22 MHz (13.6-meter wavelength). In good weather it could detect aircraft flying at 10,000 feet as far as 80 miles away. Twenty more stations were soon ordered.

Finally, in December 1937, the cabinet allotted "first priority" to air defense by reducing the ratio of bombers to fighters, an extraordinary reversal of the existing deterrent-based policy made possible by radar's ongoing success. A plan simple in concept, it proved more difficult to execute. Neville Chamberlain, prime minister from May 1937, not only had to contend with a territorially aggressive Hitler but also the British public's reluctance to countenance rearming. He also faced serious time constraints. A fully operational radar chain, sufficient shipments of Spitfires and Hurricanes, and a pool of trained pilots would, the Air Ministry advised him, be ready only by 1941 or 1942, and perhaps even later. Worse yet, Chamberlain could do little to reassure the public that their government was confident it could repulse the Luftwaffe.

This was because radar remained a deep secret, with knowledge restricted to certain cabinet ministers, need-to-know service officers, vetted scientists, gence analysts casually wrote the device off as a shipping detector.

The World War I success of sonar, a technology that uses sound to echolocate bodies in water, had blinded Berlin to the possibilities of radar. During that war the powerful British Royal Navy had developed the ability to hunt German U-boats acoustically. After the armistice it had continued to develop the technology.

and selected technical personnel. Should the Germans learn of this effective technology, they would surely target the radar stations. Partly to keep his ace in the hole classified, Chamberlain would be forced to negotiate ill-starred arrangements with Germany, such as September 1938's Munich Agreement.

When war came, it came too early for radar to be flawless. The antennae, summarized Watson-Watt in the summer of 1940, were "not yet nearly as good as we would have liked; calibration seldom complete; . . . Range-finding good; direction-finding fairly good; height finding, as always a delicate and difficult operation." Certifying altitudes outside of a 5,000- to 25,000-foot band, as indicated by Watson-Watt, proved troublesome. In fact radar did not overcome these problems until 1941-43 with the installation of a powerful new device, the cavity magnetron, which generated microwave frequencies and allowed much more sensitive detection, and the introduction of such refinements as motorized rotation mechanisms for the antennae and a map-based position indicator, as well as the construction of a second chain.

Yet the still-buggy radar nevertheless provided the breathing room critical for Dowding's fighters during the Battle of Britain. Nations without radar, such as France, Belgium, Holland, and Poland, had rapidly fallen victim to Hitler's fleets of bombers. Reichsmarschall Hermann Goring, who ran the Luftwaffe, believed that Britain would crumple within a month, paving the way for a German seaborne invasion. After all, he had some 2,800 aircraft at his disposal; Fighter Command had only 700 Spitfires and Hurricanes. Even these would have been useless had it not been for radar.

The four-phased Battle of Britain began on July 15, 1940, when Luftwaffe bombers, protected by their figher escorts, began attacking British coastal convoys and ports. The second-and most decisive-phase opened in mid- August with Operation Adler (Eagle), a determined campaign to destroy the Royal Air Force by targeting airbases, communications centers, and the occasional radar installation. Fighter Command was barely able to stave off the attacks. On September 7 the Luftwaffe began the third phase by switching its efforts to bombing London and other cities during the day in an unsuccessful effort to inflict a knockout blow to civilian morale. Ironically, the larger formations made them easier to track. Finally, in early October Goring permanently postponed the invasion but began concentrating on a nighttime blitz to terrorize the population. In darkness, bombers could fly higher and were more difficult to catch, though their bomb aiming and navigation suffered. But by then Britain had won its battle. A year later, the introduction of small, fighter-mounted radar sets helped end the bombing. Radar, crowed Watson-Watt, had multiplied the value of the fighters by a factor of three, "and perhaps by five."

On the morning of August 15, 1940, when the radar operators registered activity on their oscilloscopes, they had in fact picked up the Luftwaffe's most determined single bombing effort, a fleet of more than 1,100 aircraft. With separate formations approaching from different directions, radar provided no less than an hour's warning-plenty of time to scramble fighters. By the end of the day, Allied pilots had shot down 75 German aircraft, flying over 2,000 sorties. Many German pilots simply abandoned their missions and raced for home. It was an ultimately unsustainable rate of attrition.

While still greater challenges lay in the future, in the form of the V-1 and V-2 rockets, radar aided immeasureably in saving liberal democracy. That magnificent achievement did not, however, save Watson-Watt from a later spot of bother with the police. In 1954 he was caught speeding by the very device he had invented. Tickled by the news story, an anonymous poet wrote this bit of doggerel:

Pity Sir Robert Watson-Watt
Strange target of his radar plot
And thus, with others I could mention,
A victim of his own invention.