VENONA• 559German professor in Norway, who claimed that Heisenberg was en-
gaged on developing a U-235 bomb and ‘‘a power machine.’’
The focus of the British attention always centered on the Vemork
plant, where SIS had acquired some very detailed information about
the world’s principal source of heavy water. Initially SIS’s informa-
tion about the performance of the Norsk Hydro under German occu-
pation came from Professor Leif Tronstad, who had arrived in Britain
in the autumn of 1941, but by March the following year SIS estab-
lished contact, through Tronstad, with his friend Dr. Jomar Brun, the
plant’s chief engineer, who was in charge of production and was will-
ing to communicate with London via letters hidden in toothpaste
tubes and smuggled into Sweden. In April 1942 the Directorate of
Tube Alloys, based on Brun’s messages, reported that the Germans
had doubled the number of electrolysis cells to 18 and recommended
that the production of heavy water should be terminated, and by May
Special Operations Executive(SOE) was examining the problem.
However, it was not until October 1942 that a small four-man SOE
mission, codenamedswallowand led by Jens Poulsson, parachuted
into the area to guide in a larger force of commandos. This attempt
ended in disaster in November when the two gliders carrying the
raiders plunged into a mountain. One of the Halifax tow-aircraft was
also lost, and the few survivors of the crash were murdered by the
Nazi occupation troops. A further, less ambitious operation,gun-
nerside, landed safely in February 1943 to link up with theswal-
lowteam, and together they launched a successful raid on Vemork
10 days later. After the successful destruction of the electrolysis
cells, the entire party skied across Norway in an epic journey to
safety in Sweden.VENONA.The generic code name given in the 1960s to the signals
intelligence source originally known asbride. Based on pages of
one-time pads(OTP) that inexplicably had been reprinted by the So-
viets and reused,GCHQparticipated in an Anglo-American project,
lasting from 1944 to 1979, to trace Soviet cable traffic exchanged
with Moscow during World War II. Where British and American
cryptanalysts could find a transmission of innocuous lend-lease cargo
lists—which were recorded elsewhere in plain text—that had been
encrypted using a duplicated OTP page, they were able to read some