"THE HINGE OF FATE" “WINDOW” REDUCES BOMBER LOSSES

Press, Volume LXXXVI, Issue 26266, 10 November 1950, Page 6

"THE HINGE OF FATE" “WINDOW” REDUCES BOMBER LOSSES

[By the Rt. Hon. WINSTON CHURCHILL] XXIV

Farlv in 1943 the radar equipment fortnight bombing was readyfor operations. It was issued to finder group which, copying the Ger man example of Kanip J lA^, r J‘, p P,a rl i er ’ we had formed some months earlier. Success was immediate. Nor did 1U usefulness stop at b umb ?, n S s%rr” d For some time our aircraft had carried airborne radar for detecting surface vessels at sea. Thu was caffed Abv. But in the autumn of 1942 the Ger mans had begun to fit .. with special receivers for detecting the signals which it sent out. They were thus enabled to Umeto avoid attack. As a result Coastal mand successes in sinking u_boats h b r dined, and our losses in merchant shinning increased. H2S was adapted for use in the ASV role with striking advantage. In 1943 it made a definite contribution to the final defeat of the U-boats. But until it could be got ready I had to ask the President for help, which was granted in lull measure. Submarine detection was not our only problem in this area The Germans had established two long-range beam stations for enabling air ? craft and U-boats to navigate far out in the Bay and the Western Approaches. One of these was near Brest, and the other in North West Spam. Our Ambassador at Madrid came w hear about the Spanish station, but instead of trying to get the Spaniards to close it down, which would nave involved us in endless legal and diplomatic controversy, we were advised by Dr. R. V. Jones to use it ourselves. By taking photographs of the equipment we were able to learn how it worked, and henceforward our aircraft and lighting ships were supplied with a first-class position-finding service which they snared happily with the enemy. Coastal Command were in fact able to use it to a greater extent than the Germans themselves, and it was so efficient that we built several similar beacons for service in Australia and the Pacific.

“Window” As early as 1937 Professor Lindemann had prompted me to make a very simple suggestion to the Air Defence Research Committee. This was to scatter from the air packets of tinfoil strips or other conducting material cut to a special length, so as to simulate a bomber on the enemy’s Radar screens. If a cloud of these were droppea by our aircraft the enemy fighters would not be able to tell which were our bombers and which were our tin-foil strips. This was later called “Window.” The experts were doubtful, and the idea had not been tested until four years later, when, early in 1942 at Lindemann’s instigation highly secret trials were held. These were conducted by Dr. Jackson, one of our leading spectroscopists, who had joined the Air Force early in the war. and had distinguished himself as a night fighter pilot. The tests were successful and thereafter “Window” was rapidly developed. At , first sight it seemed that ttyese decoys would have to be as large as aircraft in order to give as good an echo. But if they were cut to the exact length to respond to the enemy Radar, this was unnecessary, and they gave a very much stronger echo for their size than an untuned mass of metal like an aeroplane. An easy and clever way of making such ‘‘tuned dipoles,” as they are known technically, was worked put in 1942, after a certain amount of stimulation from above. It was found that strips of paper with one side metallised, such as is often used to wrap up chocolate, were quite sufficient, if cut to the right length, to reflect radio waves strongly. Bundles of strips of this sort, weighing only a few pounds, thrown out of an aeroplane would flutter down in clouds several yards across, and give Radar echoes almost exactly like those produced by ordiriary bombers. It was hoped that we might be able to confuse the German Radar if a good many bombers strewed clouds of sueh paper strips about the sky, which would give spurious radio echoes and make it difficult to distinguish the echo of the real aircraft. As they would only be blown along

by the wind, the echo from the alrcr.fi moving at hundreds of miles an haul could, in principle, be disentaiwlM from the others. But this would S very difficun to do in the few minute! available, and we reckoned that it would hamper, if not prevent, accur ate gun-laying by the anti-aircraft batteries, and make it very difficult the Radar operators in charge of th. German ground control to guide th! defending fighters to the attackinr bombers.

An Air Force Argument Our bombers came to hear of it and •wanted to use it at once to save their machines. But the snag was obvioiai The device was so simple and so effective that the enemy might copy it and use'it against us. If he started to bomb us again as he had done in 1940, our own fighters would be equally baffled, and our own defence system be equally frustrated. Fighter Command accordingly wanted the secret kept, at any rate till we had found an antidote. Tense controversy ensued. On June 22 1943, I convened a Staff Conference of the heads of Bomber and Fighter Command to decide upon the use of “Window" in bombing operations. We guessed that the Germans must have thought of the devieg, but even if they adopted it. the decline of their bomber force, and the mounting strength of our air attack on Germany would give us the balance of advantage. Our experts were cqnvinced that its large-scale introduction would reduce our bomber casualties by more than a third. We therefore decided at this meeting that "Window’’ could be used as soon as there was no chance that its imitation by the Germans could affect adversely our operations in Sicily. Highest priority was therefore given to the development, production, and installation of counter-measures in this country. This work actively pursued and pressed forward, a leading part being played by Dr. Jackson. The first trial of "Window" was made in a raid on Hamburg on July 24, 1943. Its effects surpassed expectations. Heated controversies, which we intercepted, between the German ground control operator! and the pilots in their fighter planes, showed the confusion which arose. For some months our bomber losses dropped to nearly half. And up to the end of the war, although the German fighter planes increased fourfold, our bomber losses never reached the same level that had been fered before "Window” was used. The advantage gained by its introduction was maintained by a series of other new radio counter-measures and tactics.

There was, and still is, some argument as to whether we should have started using “Window” earlier. So many factors have to be considered that it is difficult to give a sharp-cut answer. Nobody could be certain how strong the German bomber force was in the summer of 1943, and it would have been very discouraging for our people if bombing attacks had begun again and our defences had proved less effective than three years earlier. On the whole, it may be claimed that we released it at about the right time. We learnt after the war that a similar proposal had been made by a German technician. Goering was quick to realise its danger to the defence. All papers relating to it were at once Impounded. and the strictest orders issued that it should never be mentioned. Before we started using it they refrained for exactly the same reason* that had made us hesitate tor so long. The Germans used it ultimately during the winter and spring of 1943-44, but by then their bombing effort was dying, and they pinned their faith to rockets and pilotless weapons. All this will be recorded In due course We have already trespassed seriously upon chronology. (To be Continued). [Copyright 1950 In U.S.A, by the New York Times Company and Times Inc. (publishers of Time and Life); in the British Empire by the Daily Telegraph. Ltd.: elsewhere by Internationsl Co-operation Press Service, Inc World rights reserved. Reproduction in full or in any part in any language strictly prohibited ]