In London, intelligence analysts, led by Reginald V. Jones, marveled at the quality of the information they were receiving from Paris, notably a startling document called the Wachtel Report. Delivered in September 1943, it identified the German officer in charge of the rocket program, Col. Max Wachtel; gave precise details about operations at the testing plant in Peenemünde, on the Baltic coast in Pomerania; and showed planned launch locations along the coast from Brittany to the Netherlands.
Relying on this information, the British organized several bombing raids against the plant, which delayed development of the V2 and spared untold thousands of lives in London.
In “1940-1944: The Secret History of the Atlantic Wall” (2003), the historian Rémy Desquesnes called the Wachtel Report a “masterpiece in the history of intelligence gathering.” When Mr. Jones asked who had sent the report, he was told that the source was known only by the code name Amniarix, and that “she was one of the most remarkable young women of her generation.”
Jeannie Yvonne Ghislaine Rousseau was born on April 1, 1919, in Saint-Brieuc, in Brittany. Her father, Jean, a veteran of World War I, was a senior official with the foreign ministry and, after retiring, the mayor of the 17th Arrondissement in Paris, on the Right Bank. Her mother was the former Marie Le Charpentier.
Adept at languages, Ms. Rousseau performed brilliantly at the elite Sciences Po, graduating at the top of her class in 1939. When war broke out, her father moved the family to Dinard, in Brittany, which he thought would be beyond the reach of the Germans.
When the occupying forces arrived, Mr. Rousseau agreed to act as interpreter for town officials and kept her ears open. “The Germans still wanted to be liked then,” she told The Post. “They were happy to talk to someone who could speak to them.”
In September 1940, an unidentified man asked her if she might be willing to share the information she gleaned from her conversations with the Germans. “What’s the point of knowing all that, if not to pass it on?” she recalled telling him, in her interview with The Post.
As German suspicions grew, she was arrested in January 1941 and interrogated at the prison in Rennes. She was released for lack of evidence and ordered to leave the region.
She returned to Paris and, soon after finding translation work with the businessmen’s association, ran into Mr. Lamarque, a former classmate, on a train. She described her job. Mr. Lamarque mentioned that he was organizing “a little outfit” to gather intelligence and invited her to join.
Shortly before the Normandy invasion in June 1944, the British tried to evacuate “Amniarix” to London for a debriefing. She and two fellow spies drove to Tréguier, in Brittany, where a contact was to guide them through minefields to a waiting boat. Unfortunately, the day before the rendezvous, their contact had been arrested.
After getting out of the car and walking toward the meeting place, Ms. Rousseau was arrested. As two soldiers walked her back to the car, she began speaking loudly in German, a tipoff that allowed one of her fellow agents to escape. The other agent refused to flee, fearing that when the Nazis found out that he was from Tréguier they would inflict savage reprisals on the town.
Ms. Rousseau was interrogated in Rennes, but prison officials did not make the connection between her real name and her assumed surname, Chauffour.
She was sent to Ravensbrück, the women’s concentration camp, where bureaucratic bungling again came to her aid. She gave her real name to camp officials, who never made the connection between her and the dossier, sent separately, that identified “Madeleine Chauffour” as part of an espionage ring.
She was later sent to Torgau, a camp in Saxony attached to a munitions and explosives factory, along with 500 other prisoners. Determined to take a stand, she approached the camp commander and announced, in German, that she and her fellow Frenchwomen were prisoners of war and that under the Geneva Convention they could not be made to manufacture weapons.
She was sent back to Ravensbrück, where befuddled officials, after failing to determine who exactly Jeannie Rousseau was, sent her to a punishment camp in Königsberg, which she described tersely as “a very bad place.”
It was so bad that she and two friends concealed themselves in a truck carrying prisoners with typhus back to the gas chambers at Ravensbrück. Arriving at the camp, they sneaked into the barracks.
The ruse worked only briefly. An informer gave them up, and they were sent for harsh treatment to an inner prison, where they were given half rations and assigned to the dirtiest work details.
Ms. Rousseau was close to death when the Swedish Red Cross came to the camp in 1945, in the waning weeks of the war, with a list of prisoners, Ms. Rousseau among them, whose release they had negotiated.
While being treated for tuberculosis, she met Henri de Clarens, a fellow patient who had been imprisoned in Buchenwald and Auschwitz. They married. Mr. de Clarens, a bank manager, died in 1995.
In addition to her son, she is survived by a daughter, Ariane de Clarens, and four grandchildren.
After the war, Ms. de Clarens did freelance translating for the United Nations and other organizations. She rarely spoke in public about her wartime exploits.
“After the war, the curtain came down on my memories,” she told The Post. She added: “What I did was so little. Others did so much more. I was one small stone.”
She was made a member of the Legion of Honor in France in 1955 and a grand officer of the Legion in 2009. She was awarded the Resistance Medal and the Croix de Guerre.
In 1993, the director of central intelligence, R. James Woolsey, presented her with the Seal Medallion (now Medal) “for heroic and momentous contribution to Allied efforts during World War II as a member of the French Resistance.”
Mr. Jones was at her side to receive the first R. V. Jones Intelligence Award, now given to agents whose work displayed “scientific acumen applied with art in the cause of freedom.”