Editing V-1 flying bomb (section)

==Countermeasures in England==
===Anti-aircraft guns===
[[File:The British Army in the United Kingdom 1939-45 H39728.jpg|thumb|left|A battery of static QF 3.7-inch guns on railway-sleeper platforms at [[Hastings]] on the south coast of England, July 1944]]
The British defence against German long-range weapons was known by the codename [[Operation Crossbow#V-1 defence|Operation Crossbow]] with [[Operation Diver]] covering countermeasures to the V-1. [[Anti-aircraft]] guns of the Royal Artillery and [[RAF Regiment]] redeployed in several movements: first in mid-June 1944 from positions on the [[North Downs]] to the south coast of England, then a cordon closing the [[Thames Estuary]] to attacks from the east. In September 1944 a new linear defence line was formed on the coast of [[East Anglia]], and finally in December there was a further layout along the [[Lincolnshire]]–[[Yorkshire]] coast. The deployments were prompted by changes to the approach tracks of the V-1 as launch sites were overrun by the Allies' advance.{{Citation needed|date=January 2021}}

On the first night of sustained bombardment, the anti-aircraft crews around Croydon were jubilant—suddenly they were downing unprecedented numbers of German bombers; most of their targets burst into flames and fell when their engines cut out. There was great disappointment when the truth was announced. Anti-aircraft gunners soon found that such small fast-moving targets were, in fact, very difficult to hit. The cruising altitude of the V-1, between {{cvt|600|and|900|m}}, meant that anti-aircraft guns could not traverse fast enough to hit the missile.<ref>{{Cite web | first=Kennedy | last=Hickman | title=World War II: V-1 Flying Bomb | url=https://www.thoughtco.com/world-war-ii-v-1-flying-bomb-2360702 | date=10 December 2019 | access-date=11 March 2023 | website=ThoughtCo.com | language=en}}</ref>

The standard British [[QF 3.7-inch AA gun|QF 3.7-inch]] mobile gun could not cope with the altitude and speed of the V-1. However, the static version of the QF 3.7-inch, designed for a permanent concrete platform, had a faster traverse. The cost and delay of installing new permanent platforms for the guns was found to be unnecessary as a temporary platform devised by the [[Royal Electrical and Mechanical Engineers]] and made from [[Railroad tie|railway sleepers]] and rails was found to be adequate for the static guns, making them considerably easier to re-deploy as the V-1 threat changed.{{sfn|Dobinson|2001|p=436}}{{efn|This was known as a ''Pyle platform'', after the head of Anti-Aircraft Command, General [[Frederick Pile]].}}

The development of the [[proximity fuze]] and of [[History of radar#Centimetric Radar|centimetric]], 3&nbsp;[[gigahertz]] frequency [[fire control radar|gun-laying radars]] based on the [[cavity magnetron]] helped to counter the V-1's high speed and small size. In 1944, [[Bell Labs]] started delivery of an anti-aircraft [[Kerrison Predictor|predictor]] [[fire-control system]] based on an [[analogue computer]], just in time for the [[Allied invasion of Europe]].<ref>{{Cite magazine | url=https://www.wired.com/story/the-american-scientists-who-saved-london-from-nazi-drones/ | title=The American Scientists Who Saved London from Nazi Drones | first=Jamie | last=Holmes | date=4 August 2020 | magazine=[[Wired (magazine)|Wired]] | access-date=11 March 2023}}</ref>

These electronic aids arrived in quantity from June 1944, just as the guns reached their firing positions on the coast. Seventeen per cent of all flying bombs entering the coastal "gun belt" were destroyed by guns in their first week on the coast. This rose to 60 per cent by 23 August and 74 per cent in the last week of the month, when on one day 82 per cent were shot down. The rate improved from thousands of shells for every one V-1 destroyed to 100 for each. This mostly ended the V-1 threat.{{sfn|Dobinson|2001|p=438}} As [[Frederick Alfred Pile|General Frederick Pile]] put it in an April 5, 1946 article in the London ''[[The Times|Times]]'': "It was the proximity fuse which made possible the 100 per cent successes that A.A. Command was obtaining regularly in the early months of last year...American scientists...gave us the final answer to the flying bomb."{{sfn|Holmes|2020a|p=360}}

===Barrage balloons===
Eventually about 2,000 [[barrage balloon]]s were deployed, in the hope that V-1s would be destroyed when they struck the balloons' tethering cables. The leading edges of the V-1's wings were fitted with Kuto cable cutters, and fewer than 300 V-1s are known to have been brought down by barrage balloons.<ref>{{cite magazine|url=http://www.airpower.maxwell.af.mil/airchronicles/apj/apj89/hillson.html |title=Barrage Balloons for Low-Level Air Defense |access-date=2007-04-16 |url-status=dead |archive-url=https://web.archive.org/web/20070202050407/http://www.airpower.maxwell.af.mil/airchronicles/apj/apj89/hillson.html |archive-date=2 February 2007 |magazine=Air & Space Power Journal |date=Summer 1989}}</ref>{{sfn|Zaloga|2005|p=34}}

===Interceptors===
{{More citations needed section|date=January 2021}}
The Defence Committee expressed some doubt as to the ability of the [[Royal Observer Corps]] to adequately deal with the new threat, but the ROC's Commandant [[Finlay Crerar|Air Commodore Finlay Crerar]] assured the committee that the ROC could again rise to the occasion and prove its alertness and flexibility. He oversaw plans for handling the new threat, codenamed by the RAF and ROC as "Operation Totter", which included a proposal whereby ROC posts would fire 'Snowflake' illuminating rocket flares in order to alert RAF fighters to the presence of a V-1.[[Image:The Royal Observer Corps in Britain, 1943 TR1444.jpg|thumb|left|upright|ROC personnel preparing a battery of 'Snowflake' rocket flares.]]

Observers at the coast post of [[Dymchurch]] identified the very first of these weapons and within seconds of their report the anti-aircraft defences were in action. This new weapon gave the ROC much additional work both at posts and operations rooms. Eventually RAF controllers actually took their radio equipment to the two closest ROC operations rooms at Horsham and Maidstone, and vectored fighters direct from the ROC's plotting tables. The critics who had said that the Corps would be unable to handle the fast-flying jet aircraft were answered when these aircraft on their first operation were actually controlled entirely by using ROC information both on the coast and at inland.

The average speed of V-1s was {{cvt|550|km/h}} and their average altitude was {{cvt|1000|m}} to {{cvt|1200|m}}. Fighter aircraft required excellent low altitude performance to intercept them and enough firepower to ensure that they were destroyed in the air (ideally, also from a sufficient distance, to avoid being damaged by the strong blast) rather than the V-1 crashing to earth and detonating. Most aircraft were too slow to catch a V-1 unless they had a height advantage, allowing them to gain speed by diving on their target.

When V-1 attacks began in mid-June 1944, the only aircraft with the low-altitude speed to be effective against it was the [[Hawker Tempest]]. Fewer than 30 Tempests were available. They were assigned to [[No. 150 Wing RAF]]. Early attempts to intercept and destroy V-1s often failed, but improved techniques soon emerged. These included using the airflow over an interceptor's wing to raise one wing of the V-1, by sliding the wingtip to within {{cvt|6|in|cm}} of the lower surface of the V-1's wing. If properly executed, this manoeuvre would tip the V-1's wing up, over-riding the [[gyroscope|gyro]] and sending the V-1 into an out-of-control dive. At least sixteen V-1s were destroyed this way (the first by a P-51 piloted by Major R. E. Turner of [[356th Fighter Squadron]] on 18 June).{{sfn|Thomas|2013|p={{page needed|date=March 2020}} }}

The Tempest fleet was built up to over 100 aircraft by September, and during the short summer nights the Tempests shared defensive duty with twin-engined [[de Havilland Mosquito]]s. Specially modified [[P-47M|Republic P-47M Thunderbolts]] were also pressed into service against the V-1s; they had boosted engines ({{convert|2,800|hp|kW|order=flip|abbr=on|disp=or}}) and had half their .50 calibre (12.7&nbsp;mm) machine guns and half their fuel tanks, all external fittings and all their armour plate removed to reduce weight. In addition, [[North American P-51 Mustang]]s and [[Rolls-Royce Griffon|Griffon]]-engined [[Supermarine Spitfire]] [[Supermarine Spitfire (Griffon powered variants)#Mk XIV (type 379)|Mk XIVs]] were tuned to make them fast enough. At night airborne radar was not needed, as the V-1 engine could be heard from {{cvt|10|mi}} away or more and the exhaust plume was visible from a long distance. [[Wing Commander]] [[Roland Beamont]] had the 20&nbsp;mm cannon on his Tempest adjusted to converge at {{cvt|300|yd|m}} ahead. This was so successful that all other aircraft in 150 Wing were thus modified.

The anti-V-1 sorties by fighters were known as [[Operation Diver|"Diver patrols"]] (after "Diver", the codename used by the [[Royal Observer Corps]] for V-1 sightings). Attacking a V-1 was dangerous: machine guns had little effect on the V-1's sheet steel structure, and if a cannon shell detonated the warhead, the explosion could destroy the attacker.
[[File:Spitfire Tipping V-1 Flying Bomb.jpg|thumb|upright=1.25|A Spitfire using its wingtip to "topple" a V-1 flying bomb]]

In daylight, V-1 chases were chaotic and often unsuccessful until a special defence zone was declared between London and the coast, in which only the fastest fighters were permitted. The first interception of a V-1 was by F/L J. G. Musgrave with a [[No. 605 Squadron RAF]] Mosquito night fighter on the night of 14/15 June 1944. As daylight grew stronger after the night attack, a Spitfire was seen to follow closely behind a V-1 over Chislehurst and Lewisham. Between June and 5 September 1944, a handful of 150 Wing Tempests shot down 638 flying bombs,<ref>[https://books.google.com/books?id=h98DAAAAMBAJ&pg=PA54 "4-Cannon Tempest Chases Nazi Robot Bomb"]. ''Popular Mechanics'', February 1945.</ref> with [[No. 3 Squadron RAF]] alone claiming 305. One Tempest pilot, Squadron Leader [[Joseph Berry (RAF officer)|Joseph Berry]] ([[No. 501 Squadron RAF|501 Squadron]]), shot down 59 V-1s, the Belgian ace Squadron Leader [[Remy Van Lierde]] ([[No. 164 Squadron RAF|164 Squadron]]) destroyed 44 (with a further nine shared), W/C Roland Beamont destroyed 31, and F/Lt Arthur Umbers (No. 3 squadron) destroyed 28. A Dutch pilot in [[No. 322 (Dutch) Squadron RAF|322 Squadron]], Jan Leendert Plesman, son of [[KLM]] president [[Albert Plesman]], managed to destroy 12 in 1944, flying a Spitfire.<ref>{{cite web | url=https://www.tracesofwar.nl/persons/42537/Plesman-Jan-Leendert.htm | title=Plesman, Jan Leendert | work=TracesOfWar.nl | language=nl}}</ref>

The next most successful interceptors were the Mosquito (623 victories),{{sfn|Sharp|Bowyer|1995|p=179}} Spitfire XIV (303),{{efn|1=Squadrons 91, 322 (Dutch) and 610. The top ace was S/L Kynaston of 91 Sqn with 21 destroyed.<ref>''Ultimate Spitfire'' (pp.&nbsp;203–204)</ref>}} and Mustang (232). All other types combined added 158. Even though it was not fully operational, the jet-powered [[Gloster Meteor]] was rushed into service with [[No. 616 Squadron RAF]] to fight the V-1s. It had ample speed but its cannons were prone to jamming, and it shot down only 13 V-1s.{{sfn|Cooper|1997|p=8}}<!-- These were the first air battles between jet-powered aircraft in history, although that distinction is usually ascribed to the battles between manned jet fighters during the Korean War in 1950.—not an air "battle", but an interception-->

In late 1944 a radar-equipped [[Vickers Wellington]] bomber was modified for use by the RAF's [[Fighter Interception Unit]] as an [[airborne early warning and control]] aircraft.{{sfn|Jackson|2007|p=217}} Flying at an altitude of {{cvt |100|ft|m}} over the North Sea at night, it directed Mosquito and Beaufighters charged with intercepting He 111s from Dutch airbases that sought to launch V-1s from the air.<ref>Ross H. Hamilton. June 2003 [http://www.airmuseum.ca/mag/exag0306.html "The Very First Awacs"] {{Webarchive|url=https://web.archive.org/web/20200115060838/http://www.airmuseum.ca/mag/exag0306.html |date=15 January 2020 }} Ex Air Gunners Association. via Commonwealth Training Plan Museum</ref>

===Disposal===
The first [[bomb disposal]] officer to defuse an unexploded V-1 was [[John Pilkington Hudson]] in 1944.<ref>{{cite ODNB |last=Self |first=Brian |date=January 2011 |title=Hudson, John Pilkington (1910–2007) |id=99289 |mode=cs2}}</ref>

===Deception===
To adjust and correct settings in the V-1 guidance system, the Germans needed to know where the V-1s were impacting. Therefore, [[Abwehr|German intelligence]] was requested to obtain this impact data from their agents in Britain. However, [[Double Cross System|all German agents in Britain had been turned]] and were acting as double agents under British control.{{Citation needed|date=January 2021}}

[[File:Flying Bomb- V1 Bomb Damage in London, England, UK, 1944 D21237.jpg|thumb|Aftermath of a V-1 bombing, London, 1944]]
On 16 June 1944 British double agent ''Garbo'' ([[Juan Pujol García|Juan Pujol]]) was requested by his German controllers to give information on the sites and times of V-1 impacts, with similar requests made to the other German agents in Britain, ''Brutus'' ([[Roman Czerniawski]]) and ''Tate'' ([[Wulf Schmidt]]). If the Germans had been supplied these data, they would have been able to adjust their aim and correct any shortfall. However, the double agents would  have been endangered because there was no plausible reason why they could not supply accurate data; the impacts would be common knowledge amongst Londoners and very likely reported in the press, which the Germans had ready access to through the neutral nations. As [[John Cecil Masterman]], chairman of the [[Twenty Committee]], commented, "If, for example, St Paul's Cathedral were hit, it was useless and harmful to report that the bomb had descended upon a cinema in [[Islington]], since the truth would inevitably get through to Germany ..."{{sfn|Masterman|1972|pp=252–53}}

While the British decided how to react, Pujol played for time. On 18 June it was decided that the double agents would report the damage caused by V-1s fairly accurately and minimise the effect they had on civilian morale. It was also decided that Pujol should avoid giving the times of impacts and should mostly report on those which occurred in the northwest of London, to give the impression to the Germans that they were overshooting the target area.{{sfn|Crowdy|2008|pp=273–74}}

While Pujol downplayed the extent of V-1 damage, trouble came from ''Ostro'', an {{lang|de|[[Abwehr]]}} agent in [[Lisbon]] who pretended to have agents reporting from London. He told the Germans that London had been devastated and had been mostly evacuated as a result of enormous casualties. The Germans could not perform aerial reconnaissance of London and believed his damage reports in preference to Pujol's. They thought that the Allies would make every effort to destroy the V-1 launch sites in France. They also accepted ''Ostro''{{'}}s impact reports. Due to [[Ultra (cryptography)|Ultra]], however, the Allies read his messages and adjusted for them.{{sfn|Masterman|1972|p=254}}

[[File:Bundesarchiv Bild 146-1981-004-19, Max Wachtel.jpg|thumb|upright|Max Wachtel]]
A certain number of the V-1s fired had been fitted with radio transmitters, which had clearly demonstrated a tendency for the V-1 to fall short. {{lang|de|[[Oberst]]}} Max Wachtel, commander of Flak Regiment 155 (W), which was responsible for the V-1 offensive, compared the data gathered by the transmitters with the reports obtained through the double agents. He concluded, when faced with the discrepancy between the two sets of data, that there must be a fault with the radio transmitters, as he had been assured that the agents were completely reliable. It was later calculated that if Wachtel had disregarded the agents' reports and relied on the radio data, he would have made the correct adjustments to the V-1's guidance, and casualties might have increased by 50 per cent or more.{{sfn|Jones|1978|p=422}}{{sfn|Crowdy|2008|p=280}}

The policy of diverting V-1 impacts away from central London was initially controversial. The War Cabinet refused to authorise a measure that would increase casualties in any area, even if it reduced casualties elsewhere by greater amounts. It was thought that [[Churchill]] would reverse this decision later (he was then away at a conference); but the delay in starting the reports to Germans might be fatal to the deception. So Sir [[Findlater Stewart]] of [[Home Defence Executive]] took responsibility for starting the deception programme immediately, and his action was approved by Churchill when he returned.{{sfn|Montagu|1978|pp=151–58}}