Thiel, his team and his family moved to Peenemünde in summer 1940. The Thiel family lived in Karlshagen Hindenburgstraße 56, in the housing complex of Peenemünde, next to Klaus Riedel and his family. Thiel was now head of the development division and scientific deputy of Werhner von Braun.
In 1940 many new scientists were recruited in order to speed up the R&D of the A4. Chemist Gerhard Heller became a very important co-worker of Thiel.
 | Thiel (2nd from right), with his staff at the testing range
VII in Peenemünde in front of the A-4 testing sample 3, which was launched on
August 16, 1942 at 12.15 CET. From left to right: Ing. Hueter, Ing. Hainisch, head of testing range Ing. Schwarz, Ing. Münz, Dr. Hackh, Ing. Zoike, Dr. Thiel and Dr. Schilling (source: Deutsches Museum, Munich (DMM), Deutsches Museum Archive, Peenemünde image file 23) |
The scientists’ hard and intense work on the A4 project was crowned with the first successful launch from test station VII on October 3, 1942. The rocket flew 190 km in the targeted direction and it reached a height of 85 km. The top-speed was 1,322 m/sec.
As the A4 was now showing military qualities, the NS leadership was demanding immediate implementation in war. Mass production replaced science, although the whole unit was still immature. There were many launch failures after October 3, 1942.
On 26 May 1943 very important German Army Officers visited Peenemünde. (Hitler never visited Peenemünde.) The test stand (Prüfstand) VII in Peenemünde can only be visited in a tour. Therefore the following filmstill is from a visit on 3 October 2017. On the photo you can see from left to right:
Dr. Thiel, Generalfeldmarschall Milch, Oberst i.G. Graf Stauffenberg, General d. Inf. Olbricht, Staatsrat Plendel, Großadmiral Dönitz, General d. Art. Brandt, Chief of HWA Leeb, Dr. Dornberger and Dr. von Braun
(The information of the persons is not completely correct, in DMM Plendel is listed as being between Thiel and Stauffenberg, Milch is missing and Leeb is not mentioned. On the tour Milch and Leeb are mentioned by the tour-guide, but not Plendel. The amount of persons is incorrectly mentioned in both accounts).
In 1943 Thiel and many other scientists in Peenemünde were close to nervous breakdowns. Overworked, immense pressure to succeed as well as the change from a research unit to a production facility was unbearable for the scientists. Thiel refused to declare the jet propulsion engines ready for mass production. He voiced his protest on August 17, 1943 by a verbal resignation. He wanted to habilitate in thermodynamics at a university, but Dornberger refused to accept his resignation.
During the following night from August 17 to August 18 the Royal Air
Force attacked Peenemünde (Operation Hydra). The Thiel family was killed in a
slit trench in front of their house in Karlshagen, Hindenburgstraße 56.
Walter Thiel and his family (wife Martha, daughter Sigrid and son Siegfried) were buried at the Cemetary of Honor in Karlshagen.
 |  |
| The Thiel family grave at the Cemetary of Honor in Karlshagen in its
original state. On the cross the names of his wife and children were spelt
wrongly. (source of photo: private archive of the Thiel family) | Today’s gravestone of Walter Thiel at the Cemetary of Honor in
Karlshagen. (source: private photo) |
On October 29, 1944 Walter Thiel received the posthumouos award of Ritterkreuz
des Kriegsverdienstkreuzes mit Schwertern (Knight’s Cross of the War Merit
Cross, German Cross in Silver).