Benedicte Clahn—Johannes Loyen

Benedicte Clahn and Johannes Loyen’s relationship is a long, intermittent intellectual collaboration shaped by the secrets of Operation Niflheim. In 1946, Clahn broke the code in letters about a ship bound for Greenland; Loyen joined her group as a medical consultant and worked alongside its members. Twenty years later he returned to the same unresolved correspondence, asking Clahn to reconstruct route information. Their work brought them together repeatedly, but never gave Clahn access to the expedition’s purpose or to Loyen’s later intentions.

The 1946 codebreaking group

In Hamburg in August 1946, Clahn was part of a small group examining coded letters exchanged among four people. The correspondence initially appeared to concern the transport and sale of goods, but its agreed metaphors made it difficult to decipher. Clahn recalled that the letters changed character after a new German censor joined the group, and that its members kept asking her about particular phrases. The word Niflheim became a persistent clue: she looked it up and found that it referred to a world of mists and the outermost realm of the dead.

Loyen joined the group as a forensic medicine expert who had been in Germany to help close concentration camps. The others expected him to consult on medical questions, but Clahn said that this proved unnecessary. He knew some German and soon worked on equal terms with the rest of them. Her recollection makes their association practical and collaborative: Loyen entered a group already trying to understand the letters, and his expertise did not define or dominate the work.

Breaking Operation Niflheim

Clahn made the decisive breakthrough in late September. One letter gave a forecast of the price of beans during the current week, with figures rising toward Friday. She compared the pattern with an almanac her mother had sent and recognized a possible relation to tides. Having sailed the English Channel with her father, she suspected that the figures resembled tide tables; the British fleet’s almanacs confirmed that they represented the ebb and flow of the Elbe. The group then spent three weeks working backward through the correspondence.

The letters concerned finding a ship and sailing it to Greenland. Clahn identified the operation as Operation Niflheim, but could not say what the voyage was for. The correspondence dealt with negotiating for a ship amid the postwar emergency, the possibility of sailing to Kiel and north through Danish waters, and which passages had been swept for mines. It also referred to the British blockade of the Elbe and the Kiel Canal. Clahn believed the writers understood the purpose, but said they never named it in the letters. Thus the successful decipherment established the expedition’s logistical outline without resolving its underlying aim.

Renewed collaboration and its limits

In 1966, Loyen was working for a company organizing a trip to Greenland when he asked Clahn to sit down with him and reconstruct information from the 1946 letters. Their work focused mainly on route descriptions and anchoring conditions. Clahn remembered that they spent a great deal of time on the task but were unsuccessful, and thought she might have received a fee. The old codebreaking partnership had become a second attempt at recovering practical knowledge from the same archive, but the surviving descriptions did not yield a usable reconstruction.

The association appears to have continued, or at least been renewed, around 1990 and 1991. When asked about those years, Clahn bit her lip and brought up Helen, Loyen’s wife, whom she described as very jealous. She did not explain the circumstances or say what Loyen wanted from her then. This brief, guarded response places a personal boundary around their professional history: their repeated contact is clear, but its later character and purpose remain undisclosed.

A durable but incomplete bond

Clahn said that she and Loyen may have discussed these matters once or twice, but that it had been more than twenty years since they had done so. She was raised to regard discretion as a matter of course, and her account keeps faith with that principle. She could recount how she cracked the code, describe Loyen’s place in the 1946 group, and recall their later work on the route, while still withholding or lacking the answers that would connect those episodes into a complete explanation.

The relationship is therefore defined less by intimacy than by a recurring exchange of specialized knowledge. In 1946, Clahn’s insight made the coded letters legible, while Loyen contributed as an equal member of the deciphering group. In 1966, he sought her help to recover route information from those same letters, but their effort failed. Later contact is acknowledged without clarification. Across these returns, the collaboration opens a window onto the history of the Greenland expedition while preserving its central blank: neither Clahn’s recollection nor the decoded correspondence reveals what the voyage was ultimately meant to accomplish.