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Free Balloon Operations in World War Two

Operation Albino

During the early part of the war there was a Department in Whitehall that went under the name of D.M.W.D., the name stood for Royal Navy 

Directorate of Miscellaneous Weapon Development. The name was deliberately vague, within the Department the people employed there were 

referred to as the "Wheezers and Dodgers. (W.D.)". It had no connection with the Royal Air Force or the Royal Auxiliary Air Force. This lack of 

connection was nothing new: in the Great War the Navy had quarreled over who should pilot and crew the airships in the sky and since there was 

no Royal air Force the Royal Naval Air Service was born. (R.N.A.S.). The birth of the Royal Air Force as a separate service arm  in April 1918 

caused considerable ruffling of sails in the Admiralty.

          In early 1940 Churchill summoned a meeting to discuss the possibility of firing into the sky a lethal curtain of wires on parachutes that 

would tangle around airscrews and bring the aircraft down. He told the meeting that a minefield in the sky was just the thing to bring down 

enemy aircraft. He told the meeting that he wanted a, "square of wire in the sky as big as Horse Guards Parade with parachutes to hold it in 

place". On the night of 17-18 September, 1940, a number of British barrage balloons broke loose in a gale they were whisked across the North Sea 

In Sweden and Denmark , they damaged power lines, disrupted railways and the antenna for the Swedish International radio station was 

knocked down, bearing out the findings of the 1937 report. Five balloons were reported to have reached Finland . A report on the damage and 

confusion reached the British War Cabinet on 23 September, 1940. Winston Churchill then directed that the use of free-flying balloons as weapons 

against Germany was a matter for development.

The Air Ministry initially poured cold water on the idea, as the Ministry of Aircraft Production felt balloons would be ineffective weapons and 

would need much manpower and gas to deploy. However, their rivals in the Admiralty took up the idea with more enthusiasm. They decided 

balloons were low cost and were likely be able to do their job without servicemen being at risk. The rivalry between the two arms of the service 

over free balloons continued throughout the war with some very harsh comments made by both sides.

          A certain Commander Fraser, who worked in the Admiralty Boom Defence, supplying all grades of wire rope for Navy use, came up with an 

idea to send a cloud of wire skyward by attaching it to free floating balloons. He knew of a device that had been invented known as the "long 

aerial mine", that would project a network of wire and bombs skyward by release from a bomber flying some distance ahead of enemy aircraft. Dr 

F. D. Richardson (who became Director of the Nuffield Research Group  post-war) was given the task of looking at Fraser's idea. After some weeks  

Richardson found quarters at Cardington and step by step, began to make and modify the first Free Balloon Barrage.

          His concept was to produce hundreds of hydrogen filled rubber balloons, to which was attached a yellow box, like a round biscuit tin, and a 

wooden spool with 2000 feet of wire to which a parachute was attached. He envisaged the balloon being released with its 22lb payload. On the 

top of the bomb was a circular slow burning fuse that was ignited at the time of launch. As this slowly burnt it caused one of seven bags of sand to 

fall away allowing the balloon more buoyancy and altitude.

                   In addition, after a certain time it would reach a specific altitude and a atmospheric pressure switch on board would activate. This 

switch would cause two events: first cause the spool of wire to unravel with the parachute at the bottom and secondly to arm the bomb on a 

board underneath the balloon. When an aircraft struck the cable it caused a shock wave that caused two other events: the parachute opened and 

was dragged under the wing and as the aircraft moved forward the parachute and piano wire ran over the leading edge of the wing and behind the 

plane, at the same time the bomb began to descend until it came into contact with the wing where a small spring rim on the bomb became 

pressed over and the bomb exploded.

          But like many concepts and ideas, the practical testing of this idea was fraught with problems. The behaviour of these balloons was quite 

unpredictable . After a certain time aloft it was built in to the design that a "fail-safe" mechanism, a timer, would cause the bomb to explode, also 

after one hour the fuse would reach the bomb detonator and ignite the bomb. Thus destroying it and rendering it from descending to earth in an 

unsafe manner.       However theory and reality were as always not what one expected. The balloon might raise up to its operating height become 

armed and then descend to earth in a dangerous state because the "fail-safe" timer had failed or the fuse had gone out, the fuses were particularly 

sensitive to rain and moisture. On contact with the ground it might or might not explode dependent on what and how it struck the ground. The 

balloon might leak hydrogen, the "fail-safe" timer fail and descend to the ground although unarmed it was still a dangerous unexploded device. 

One of the early problems was that the height adjusting mechanism made up of seven small bags filled with sand failed to work. On the 24th March 

1941 at a meeting of the Night Air Defence Committee, Winston Churchill insisted they continue with trial of the Free Balloon Barrage.

An interesting and secret memo dated 1st June 1941 shows the dismissive attitude to the free balloon barrage adopted by J. Whitworth Jones 

Director of Flying Operations. He states "When the Free Balloon Barrage was first inflicted by an enthusiastic Admiralty on a reluctant Air Ministry 

with the connivance of a cigar smoking Prime Minister, the latter said that great care was to be taken that this brilliant weapon did not fall into 

the hands of the enemy.", he goes on to complain about the consistent failures of the balloons but that "a suspicious Air Ministry felt that the spirit 

of the Prime Ministers original instructions must be observed." He then points out that following a small scale trial of 220 balloons at Liverpool, 

with fuses set to self destroy after one hour, " The Germans were kind enough to inform us in their communiqué that some of these units had been 

picked up in Sweden." ! The Air Ministry and The Admiralty were never going to agree over the Free Balloon Barrage,  a number of prominent Air 

Force officers wanted it abandoned but seemed to feel that the Admiralty was pushing on with it as they were wanting to please Churchill.

          The piano wire was as much of a problem as the bomb. It was able to trail over electric railway lines , overhead power cables and seemed 

to delight in short circuiting the countryside for miles around. The wire might drape over 30,000 volt overhead lines and cause the power to leak 

to earth giving risk of electrocution. The cable might just hang tantalisingly down from the overhead lines attracting curious people to reach up 

and grab it, with fatal results.

          In Wales, trials at the Experimental Establishment at Aberporth resulted in tragedy. On 30th September 1941, a 13 year old boy, John 

Charles Butler of Owny Villa, Aberporth, Cardiganshire was fatally electrocuted when he took hold of a piece of Free Barrage Balloon wire that had 

become draped over the high tension wires, a passing soldier tried to help and was burnt and sent to hospital. Another incident was of a children's 

nurse who rushed to help the child she was looking after when he had picked up a balloon wire that was connected to the mains. Due to the 

electricity the child could not let go and the nurse grabbed the child and then she could not let go. Luckily for both of them the child's father 

rushed to their help and knocked  the cable from their hands, saving both their lives. It was decided in January 1942 to put up notices within a 25 

mile radius of the Aberporth Establishment  to warn people of the dangers of touching anything that came down from the air.

          The name "Albino" stemmed from the use of a large white rabbit that would be pinned up on the notice board at D.M.W.D. offices by a civil 

servant called Jamieson. The one individual who seemed to lead the Free Balloon Trials was a tall South African, R.N.V.R. Lieutenant T.F.W. 

Harris. On nights when the Free Barrage Balloon trials were "on", Harris would recruit volunteers from the D.M.W.D. to help out at the launch 

sites. As the trials went on a series of comical and tragic events took place.

          The whole project was classically "Top Secret" and as a result the public and indeed vast numbers of the military were kept in the dark. It 

was decided to let ARP wardens into the secret to some degree. They were vaguely warned that a new form of night defence might be used and 

advised not to touch them if they came down in the hours of darkness. The mechanical failures of these new balloon weapons were many. In 

addition the paths these balloons took on release was unpredictable despite the meteorologists giving confident forecasts about the wind and 


          The balloons were supposed to go up and saturate a limited area of sky. However once launched they were fortune to the elements and the 

wind could change resulting in balloons being launched in London ending up in Devon ! The telephone calls from worried citizens were legend. It 

was decided to form a band of retrievers to travel far and wide to retrieve these devices when they had been found. On one occasion they went 

to Piddletrenthide, in Dorset where a police officer proudly showed them two Free Balloon units lying side by side in his garden. Attached to each 

one was only two feet of wire. The retrievers were astounded when they were told that he had found them in a field and not knowing what they 

were had cut off the wire and tied the two, armed bombs to his bike handlebars and cycled the mile home! Had the firing pin been hit it would 

have been fatal for the policeman.

          They were called to a farm in Hampshire by a farmer who had found one of the yellow bombs. On asking where it was to be found on the 

farm, he told them that it was now on his kitchen table, but it was quite safe as he had taken it to pieces! He had dismantled it more by luck than 


          On 29th December 1940 this entire trial was fraught with technical difficulties but Churchill thought it could be made a winner. He ordered 

a full scale test against the enemy. D.M.W.D. were unhappy but they went ahead. That night the Germans launched a massive fire raid on London. 

The RAF was given instructions to assemble several hundred men and 800 lorries and trailers and other equipment across a two mile arc in 

Hatfield. At each site 12 foot high tents were erected and in these the 10 foot balloons were inflated with hydrogen.

          They launched some 2000 free balloon units at the height of the German raid. The statistics did not make for happy reading.

Over three zones where the balloons were released some 30% failed near the launch site due to problems with the wire spool, some 15% landed in  

London , one in Buckingham Palace . In the last zone another 30% failed to perform as planned. Some were found on the South Coats and 

several made it over the English Channel to France .

          The following dawn a massive retrieval operation began at first light. Anyone who could walk and look for the bright yellow bombs was 

commandeered, Boy Scouts, Fireman, Policemen, and any spare service personnel the military could spare.

The bombs were clearly marked in large lettering: "DANGER - DO NOT TOUCH", however this seemed to make the desire to pick them up almost 

impossible to ignore. One shop keeper was found cycling up the road with four of the armed bombs tied by their wire to his handlebars! A number 

of bombs were hung up in trees and some had hit houses.

          One farmer had fourteen land on his farm and he had dragged all of them to a corner of one field, where he had then laboriously covered 

the units in cow dung because he thought that would stop them blowing up!

          Later even though the results were not good it was decided to carry out a small scale test in Bedfordshire, using 200 balloons. Despite 

having some 50 sailors to help with recover it was impossible to see these devices easily on foot. In desperation they hired fourteen horses and 

carried out the search more rapidly and successfully on horseback. This small scale trail showed that the problems with the device centered 

around, the wire on the spool not unreeling smoothly when the unit got to its operating height. This was found to be due to the hole in the bomb 

board not being smooth enough and making the springy wire kink. The other problem was the safety valve that prevented the balloon raising 

above the operating height of 14,000 to 18,000 feet was jamming and the balloon would rise too high and burst sending it lethal payload down to 


          The wind was so unpredictable that the balloons could travel miles across the sea, ending up in France , Ireland , Sweden and Holland

A Dutch Air Raid Warden reported in April 1942  of the finding of one of the FBB units. The warden wrote that they had "found a small yellow 

parachute of 40 cm diameter with a wooden board on it. Connected to the parachute was a thin steel cable.

 On the wooden board was glued a paper with the following text:

 "F.B.B. Assembly Sheet

 Assembly No. 24 D 53

 Bomb board No. A 4450

 Bomb No. 8432

 Spool No. 14997

 Stabilising parachute No. 411592

 Drogue Parachute No. 427382

 Date of assembly L H 9/6/41

 B M D no. 34234.

 J. Downes

          On the centre of the board was mounted a 12 cm high cartridge with 4 small cylinders around it. One of these small cylinders had a lever on 

it and was marked with a label with the text "DANGER". A fifth cylinder was filled with a small parachute made of white silk." The yellow 

parachute ", was not a parachute, it was in fact a canopy that covered the delicate surface of the bomb board to prevent damp and rain affecting 

the slow burning fuses from the weather.

          The Germans were fully aware of the potential use and dangers from this device and by the British stupidly ensuring that every one sent out 

had an explanatory label stuck to it, including the name of the assembly worker, certainly did not help matters.

The British public and most of the military did not know about the F.B.B. but it is certain that Germans knew everything. It is interesting to see 

that far as I am aware the Germans never redesigned this to attack the British raids later in the war.

          The D.M.W.D. team set up experiments to see what happened to the safety valve and the buoyancy when the balloon was subjected to 

colder and colder temperatures. This they did by using a massive walk-in refrigerator on a fruit farm.

Due to the nature of the design it is not surprising that there  were several casualties from the free balloon units

          The results of the work was that they felt that by making refinements to the mechanical aspects of the balloon they could make it work.  

London area was chosen for more trial balloon launchings. It had been decided that the task of launching and ensuring the movement of all the 

necessary equipment was to be given over to Balloon Command using Balloon Squadrons. This test again showed a number of devices reaching  

France much to the puzzlement of the Resistance.

          The next operational launching was to take place at Liverpool when during a raid some 150 balloons were released. The modifications 

showed some 80% success rate but none of them were known to have hit an enemy aircraft. People in the area between Warrington and 

Taporley were on the receiving end of the 20% of failures, putting the telephone exchange out of action and causing a massive short circuit to 

high tension cables over farmland.

          Just as the Barrage Balloon personnel were getting to grips with this new weapon the Luftwaffe turned their attention to other fronts of 

war and mass bombing raids more or less ceased.

The weapon was never given a chance to show what it could do.

It has always puzzled me that the Germans never seemed to use this idea against our mass bombing raids, the prevailing winds in Germany were 

generally in the wrong direction. The concept and tactical value is good, but I suspect that German engineers who were world class at the time 

decided it was a weapon that was too "fiddly" to mass produce and since they had a few surprises such as the V1 and V2 on the drawing board 

there was no point in attempting this form of defence. In addition, in 1944 the British bombers were all  having the cable cutting devices that 

were designed to sever balloon cables as standard fitments and these would have made the use of FBB by the Germans pointless.







Once struck by a plane the drogue parachute would open and the bomb would release from the balloon. 

As the plane flew on the bomb would be drawn over the top of the wing and detonate.


 Operation Outward

 Operation Outward was the name given to a similar program of free balloon weapons. In 1937, the British determined that the damage that may 

be caused by a balloon-carried wire hitting power lines was not inconsiderable. In the winter of 1939-1940 the idea of using balloons as floating 

weapons was proposed. The concept was that balloons, launched from France , would carry transmitters and their position would be tracked by 

radio triangulation. The bomb would be released by radio control when the balloon was over enemy territory. Defeat in the Battle of France  

put possible launch sites out of British control, and the idea was shelved for a while. It was well known that a loose barrage balloon dragging its 

cable across the country would cause mayhem particularly to electric cables, shorting out circuits every where. In the winter of 1939-1940 the 

idea of using balloons to carry bombs was proposed.  It was known that one of our balloons had become loose and had drifted off to the North Sea 

where it had  landed in Sweden and the cable caused much damage to electrical services. The gem of an idea was forming in the minds of the 

scientists: the concept was to produce free balloons that would have one of two systems added. One was a long spool of cable that would release 

after so many hours over the enemy target area, as this cable dropped down it would be dragged by the balloon in the wind and hope fully hit 

power lines and cause electrical shorting and much inconvenience to the enemy. The second was to have three incendiary devices each weighing 

some 6lb, These were SIP (Self Igniting Phosphorus Grenades (Allbright & Wilson Bombs/No 76 Grenade), fixed in a sock, as these fell to the ground 

they would cause fires and damage enemy property. The balloons flew at a height of 16,000 feet and were simple to make and each cost around 

£1/- 15s in those days. The design of the German power grid was ideal to damage it by short-circuit. Germany countryside consisted of large areas 

of pine forest and heath land, making it vulnerable to incendiary attack and the Germans would have to use many people on fire watching, 

possibly diverting them from more productive war-work. In addition winds above 16,000 feet tended to go from west to east, making it harder for 

the Germans to consider a similar balloon weapon. In September 1941 the British Chiefs of Staff settled the bickering between the Admiralty and 

the Air Ministry and ordered a trial of the incendiary balloons and trailing cables. Landguard Fort at Felixstowe in Suffolk was chosen as the 

launch site. The first balloons were launched on 21st March 1942, using a mixture of Balloon Barrage personnel and it seems they caused forest 

fires near Berlin and in East Prussia . So concerned were the Germans that they gave orders for their fighter planes to shoot down any balloons. 

This gave the Admiralty what they wanted as they claimed that these balloons cost the Germans a lot of time and money to fly fighters against 

these simple, cheap balloons. In July, a second launch site was set up at Oldstairs Bay near Dover . On 12 July, 1942, a wire-carrying balloon 

struck a 110,000-volt power line near Leipzig . A failure in the overload switch at the Bohlen power station caused a fire that destroyed the 

station. This event was thought to be Outward's greatest success. Balloon launches continued, though they were frequently suspended when there 

were large air-raids on Germany as it was feared the balloons might damage Allied bombers. Sadly, they continued to cause damage in neutral 

countries - on the night of January 19-20, 1944, two trains collided at Laholm in Sweden after an Outward Balloon knocked out electrical 

lighting on the railway. The last "Outward" balloons were launched on 4 September 1944. A total of 99,142 Outward balloons were launched: 

53,343 carried incendiaries and 45,599 carried steel cables designed to damage electrical equipment.

Operation Petard

The word "Petard" is used in the phrase "hoist with one's own petard", which means "to be harmed by one's own plan to harm someone else" or "to 

fall into one's own trap," literally implying in the warfare of medieval times that one could be lifted up (hoist, or blown upward) by one's own 

bomb. It was this aptly named operation that was used to try and bring down enemy bombers by use of a series of balloons each with an aerial 

mine attached to them. The concept was that when a German raid was taking place, a vast number of these balloons would be released from the 

ground into the path of the bombers. It depended on the wind as the balloons had to drift up and towards the incoming bombers. The first trial 

took place by 30 Balloon Group in the Thames Estuary from 1000 hours onward on 7th February 1942. It was designed to try an attack enemy mine 

laying aircraft. The weapon was exactly the same as used in "Albino" except that the spool of wire became released by fuse action at a lower 

specific height, as it rose into the air. It was ordered that the balloons would be set to fly at a minimum height of 4,500 feet and the self 

destroying fuse was designed to go off at intervals of 45 minutes each, depending on the wind speed. (as the wind speed increased the self 

destroying fuse burnt much faster).

The balloons were to be released providing the wind was from the  South South East, from "Fronts" or land sites on the coast between Margate a

nd Sheppey, to the south of the interception area and Shoeburyness and the Naze to the North-West of the area.

There were two Squadron fronts, "North Squadron", based to the North of the Thames and "South Squadron", ", based to the South of the Thames

On the night of 7th February 1942, Balloon Command stood by waiting for the "Release" order from HQ Fighter Command. All British aircraft would 

be warned to stay away from the area and al Naval vessels advised the same. Headquarters AA Command also received orders not to use their 

searchlights during the duration of the operation

Ground Control Interception (GCI) and Chain Home Low (CHL) (an early form of radar), were expected to monitor the Petard units for both height 

and direction.

The "Petard" Balloons were first used against enemy aircraft on the night of the 18th/19th March1942. South Squadron at Swalecliffe, Herne Bay 

was ready at 1836 hours, the first enemy plots were spotted by Fighter Command HQ at 1956 and was some 45 miles off the Hook of Holland . At 

2001 hours the "stand-by" was given and this allowed the airmen to begin inflating their balloons in their release tents. As the enemy numbers 

increased Balloon Command gave the order to release at 210 hours.  12 enemy aircraft came in and they left the estuary at 2052 hours. A "cease 

fire" was ordered. The weather was reported as bad over Holland and as no further radar plots were seen it was decided to stand down the 

Balloon Squadrons who returned to base. at 2142 hours a second wave of 8 aircraft appeared, but there was no way for the balloons to be released 

against these. No enemy aircraft appeared to have been hit but one radar plot faded some 15 miles out to sea, so it might have been damaged. 

One other aircraft behaved quite strangely and circled around for almost an hour, presumably in difficulties, eventually it made for home. Some 

450 balloons were released, set to fly at 4,500 feet. One or two reached 11,000 feet because their wires broke off and due to the reduced weight 

they had more buoyancy.

A further release took place on the 31st March 1942, the weather was ideal for a release, no enemy aircraft were plotted in the Thames Estuary 

and the whole operation was used as an exercise. However it went badly wrong, at the end some three military were killed and seven civilians 

were wounded.

On the night in question some 1700 balloons were released, the Balloon Squadron used was No.2 Mobile Squadron of Herne Bay , led by 

Squadron Leader T. R. Poppy. Those balloon personnel doing the release were confident that it had gone well. However the utter secrecy of the 

weapon was what caused most problems. Only those who needed to know knew.

When the balloons were launched, the wind direction was fine but it seemed that many of the balloons failed to float high enough and began to 

descend back onto the mainland. Despite the fact that there had been previous launches of "Petard", an army group nearby were totally unaware 

of this weapon and on seeing these five foot diameter cream coloured balloons in the moonlight, they presumed it was an enemy weapon and 

opened fire, in many cases using tracer. Those balloons that did not catch fire, leaked, and came down to earth over a wide area of Minster. The 

leaking balloons failed to gain any great height and as the quick match fuse was burning the spool of wire began to unravel at a much lower height 

than anticipated. Many of them fouled on the high ground around the village, shorting out high tension cables and snagging on trees and hedges. It 

was thought that some 200 came down in the area. An A.R.P Warden driving around in his car on duty ran into one of the wires and got out to 

remove it, this caused the bomb to go off, and he died from his injuries the following day. At Eastchurch Station four balloons had landed, not 

knowing what they were, the personnel on the base decided to gather them up as they were probably weather balloons and four of them were 

placed in a heap in the guardroom. The making safe of these bombs was a very difficult task as the Bomb Disposal people, led by Squadron Leader 

Dinwoodie could see that they were in a very sensitive and dangerous state. The making safe took several hours. One civilian who found a Free 

Barrage Balloon and bomb in a field decided for mind boggling reasons to move it to a "safe place", It was duly placed on the ground adjacent to 

the main railway line and covered with a sack! Bomb Disposal had a very tricky job dealing with it as the self destroying device was almost on the 

point of functioning. One police man from Eastchurch awoke and on leaving for work on the 1st May a 5.a.m., and could see around 50 devices 

strung up in trees, over hedges and telephone lines. As he went to work he saw many more lying about the area.

The event caused were several Courts of Enquiry:

The death of 6030268 Private J Pullen, C.M.P. (Corps of Military Police), age 56, Son of David and Myra Pullen; husband of Rhoda Pullen. of West  

Mersea, was inquired into and was told by Private Palfrey C.M.P. that Pilot Officer Hulbert of 1 Mobile Squadron had told them between 2300 and 

2400 hours on 31st March 1942, that the explosives attached to the balloons were timed to go off within one hour. It is possible that Private 

Pullen was killed because he thought the devices would have been safe after an hour due to the self destroying devices.

In addition to the above death, two very brave men also died, 120146 Lieutenant John Percy Walton G.M. Royal Engineers and 1300551 Lance 

Serjeant Charles Frederick Bristow G.M. ,22nd Bomb Disposal Company, Royal Engineers, age 43, son of Fred and Rose Bristow; husband of Elsie 

Bristow, of Cranwell Village, were all killed. Sergeant Auten Royal Engineers was injured while working on Bomb Disposal on the Free Barrage 

Balloon units.

The dangerous legacy continued, on 5th May, at Scapsgate, a Petard device was washed ashore, one boy was killed, and one, Harry Kennett, 

seriously injured when they tried to remove the sand bags used for altitude control, as one lad thought they would be great for his budgerigar at 

home. How many more people were not killed or injured is a minor miracle.

As a result it was finally agreed to produce leaflets explaining the description and dangers of these devices and ensure that greater public 

awareness was made.  

Operation Mutton

Although not a balloon borne device, this was similar in that it involved the release of "Long Aerial Mines" also known as "Pandoras", into the path 

of oncoming German bombers by British aircraft. The concept here was to break up a formation of enemy bombers so that they flew in a much 

more random way making them more vulnerable to our fighters. This began in September 1940. Following much experimentation, the optimum 

configuration for the mine was determined.

The resulting weapon fitted into a cylindrical container 14in long and 7in in diameter, and weighed 141b.   After release from the aircraft the 

obstacle deployed.

It comprised, from top to bottom: a supporting parachute, a length of shock-absorber cord, the cylindrical container, an AAD bomb, 2,000ft of 

piano wire and, at the bottom, a second furled parachute.

When an aircraft struck the piano wire the shock wave ran up the wire, causing a weak link to break, releasing the main supporting parachute and the 

cylindrical container. As the container fell away the bomb was armed and a small stabilising parachute connected to the weapon was released. 

Simultaneously, the shockwave travelled down the piano wire and caused the lower parachute to open. This took up a position behind the aircraft 

and pulled the bomb smartly down on the aircraft.

However, in autumn 1940 Fighter Command's most difficult problem became how to counter the night raider.   The long-term answer was the Bristol  

Beaufighter, fitted with airborne interception (AI) radar, directed on to its prey by a ground-controlled interception (GCI) precision radar. But 

each of those systems was in an early state of development, and some time would elapse before they were available in quantity. In the meantime, 

anything even remotely likely to be effective against the night bombers was pressed into use, including the Long Aerial Mine. German bombers 

attacking at night did not fly in formation. Instead, they approached their targets at irregular intervals, following their radio beams. At night, the 

mines were to serve a different purpose than that originally proposed. Instead of being used to split up an enemy formation, a line of mines would 

serve as an "aircraft trap" to destroy bombers.

Somewhat obsolete Handley Page Harrow twin-engined bombers were used for aerial mine laying. The device was successful as in 1941 there 

were six German bombers destroyed by the Pandoras.


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