[3] The British lost 40 bombers and 215 aircrew, and several hundred enslaved workers in the nearby Trassenheide forced labour camp were killed.

The head of the ballistics and Munitions Section, Colonel Becker suggested that short-range anti-aircraft rockets be designed and accurate, longer-range missiles should be produced to carry gas or high explosives.

Other scientists studied the use of rockets for maritime rescue, weather data collection, postal services across the Alps and the Atlantic and a journey to the Moon.

[4] The US Office of Strategic Services (OSS) received important information about the V-2 rockets and Peenemünde from the Austrian resistance group around the priest Heinrich Maier.

[5][6][7][8] Information had reached the British Secret Intelligence Service (SIS) about German weapons development since the Oslo report of November 1939, from Royal Air Force (RAF) photo-reconnaissance photographs taken from 22 April 1943 and eavesdropping on Lieutenant-General Wilhelm Ritter von Thoma, a prisoner-of-war in Britain, who expressed surprise that there had been no rocket bombardment of Britain.

[9] Information also came from Polish intelligence, a Danish chemical engineer and from Leon-Henri Roth and Dr Schwagen, Luxembourgish enrolés de force (forced labourers), who had worked at Peenemünde and smuggled out letters describing rocket research, giving conflicting accounts of the size, warhead range and means of propulsion of the device.

H2S radar worked best over contrasting areas of ground and open water and 5 Group was to fly an approach run from Cape Arkona on the island of Rügen, to Thiessow to check time and heading.

[16] [17] The nature of the raid was not revealed to the aircrews; in their briefing, the target was referred to as developing radar that "promises to improve greatly the German night air defence organization".

8 Group RAF) Mosquitoes of 139 (Jamaica) Squadron flew to Whitebait (the codename for Berlin) to simulate the opening of a Main Force raid.

Eight Handley Page Halifaxes exploited the full moon to fly supply sorties to Europe, some to the Danish resistance movement, covered by the flight of the Main Force.

[24] About 75 per cent of the buildings were destroyed but only about 170 of the 4,000 people attacked were killed, because the soft ground muffled bomb explosions and air raid shelters in the estate had been well built.

[27] The bombers flew 20 or even 30 seconds past the timing point to the visible and inaccurate green markers from the six "shifters" and three backers-up, their bombs landing 2,000–3,000 yd (1.1–1.7 mi; 1.8–2.7 km) beyond the development works in the concentration camp.

"[30] In volume II of The Strategic Air Offensive against Germany (1961) part of the official History of the Second World War, Webster and Frankland wrote that Dornberger thought that the bombing delayed the A4 (V2) project by four to six weeks, which had been followed by many later accounts but that this was anecdotal.

[33] The official historians wrote that the transfer of production to the Harz mountains and testing to Poland must have caused some delay in remedying the numerous design failings of the device and that the killing of Thiel and Walther might have made things worse.

[34] Although research and development continued almost immediately and test launches resumed on 6 October, plans for some German V-2 facilities were changed after Hydra; the unfinished production plant for V-2s was moved to the Mittelwerk.

[36] In the 2006 edition of his book, Martin Middlebrook wrote that 23 of the 45 huts at the Trassenheide labour camp were destroyed and that at least 500 and possibly 600 slave workers were killed in the bombing.

After the Luftwaffe realised that the attack on Berlin was a diversion, about 30 Focke-Wulf Fw 190 Wilde Sau (wild boar) night fighters flew to the Baltic coast and shot down 29 of the 40 bombers lost; Leutnant Peter Erhardt, a Staffelkapitän and Unteroffizier Walter Höker flew the first operational Schräge Musik sorties in two Bf 110s.

[41] After Operation Hydra, the Germans fabricated signs of bomb damage on Peenemünde by creating craters in the sand (particularly near the wind tunnel), blowing-up lightly damaged and minor buildings and according to Peenemünde scientist Siegfried Winter, "We … climbed on to the roofs … and painted black and white lines to simulate charred beams."