MARIE-MADELEINE FOURCADE, asked what she’d done during World War II, once described herself as “the wife of an officer, the mother of a family, a member of no political party, and a Catholic.”

What she failed to mention was that she had led some 3,000 agents in Alliance, the largest and most important French secret intelligence network against the Nazis. It provided crucial information to England’s MI6 on German submarine operations, V-1 and V-2 rocket development, Nazi preparations prior to the Allied invasion of Normandy, and myriad other German plans and maneuvers.

Alliance’s work saved countless thousands of lives. The Germans hunted, imprisoned, tortured, sent to death camps, and often summarily executed hundreds of the network’s agents. One of those murdered — in vengeful fury after Paris had already been liberated by the Allies — was Fourcade’s lover and second in command, Léon Faye. Entire regional cells of Alliance were obliterated, sometimes repeatedly, only to regenerate like the severed arms of an octopus.

Fourcade was smart, wily, and beautiful, with an independent streak defiant of conservative French culture and the secondary roles to which it consigned women. Raised wealthy and cosmopolitan in Shanghai and Paris, she trained to be a concert pianist before marrying a handsome army captain, then separated from him because he was too dictatorial toward her. She worked as a radio producer, sported the latest fashions, liked driving fast cars, and earned a pilot’s license. A single mother of two young children, she was like a character out of an Alan Furst espionage thriller. Only she was real, and, for decades, her achievements were under-recognized, as were those of Alliance itself.

That is because, despite Fourcade’s efforts to remain neutral, infighting among the various resistance movements during the war determined who would reap power and prestige in the postwar period. For instance, de Gaulle resented that Alliance, for most of the war, passed its intelligence to MI6 instead of to de Gaulle’s London-based Free French. De Gaulle was also upset with Alliance because it arranged, on MI6’s orders, for de Gaulle’s rival General Henri Giraud to escape France in a daring submarine mission. President Franklin Roosevelt wanted Giraud to take charge of Vichy forces in North Africa, and Churchill capitulated to that misguided wish so as not to alienate his crucial American ally.

Following France’s liberation, the French communists underplayed the achievements of Alliance because they associated it, unfairly, with the country’s conservative and reactionary forces. That’s partly due to Alliance’s origins. Georges Loustaunau-Lacau, a fiercely anticommunist army major with a disdainful but opportunistic approach to the Vichy government, first teamed with Fourcade to build the network before turning over its operations to her. Fourcade’s focus was not Vichy but rather her handlers in British intelligence, but the communists never forgot Alliance’s early Vichy link, however tenuous.

If history is, in fact, written by the victors, a corollary is that the champions of internecine battles among those victors spin that history further. That and Fourcade’s gender explain why it took decades for Alliance to be given its proper due.

Fortunately, Lynne Olson, who has written widely about Allied efforts during the war, turns a long-overdue spotlight on Fourcade in a tense new page-turner, Madame Fourcade’s Secret War: The Daring Young Woman Who Led France’s Largest Spy Network Against Hitler. Olson’s research is comprehensive, her writing crackling, and her story astonishing.

She is wise enough to get out of the way of her compelling material, but also to shape it so that the Alliance’s complicated exploits are clear and the dozens of players in the story, many with one or more code names, can be kept straight. The book is war history, to be sure, but also an astute character portrait and a study in management and persistence under harrowing circumstances.

A woman in a man’s world, Fourcade had to win the trust of, then command and train, her ever-widening network of amateur volunteer spies — among them merchants, tradespeople, couriers, aristocrats, soldiers, police, homemakers, even a famous former child film actor. She had to emotionally absorb and acknowledge the tragedies of her fallen colleagues and honor their sacrifice while keeping Alliance encouraged enough to fight another day.

Sometimes she did this up close, working in cramped, chaotic offices or Maquis camps in the woods. Sometimes she managed her organization from London, via contact by radio. Alliance and MI6 even developed an ingenious, daring flight branch called Avia, which managed parachute drops of espionage equipment, weapons, money, and surveys to guide intelligence gathering. Agents and reports volleyed back and forth between France and England in tiny two-cockpit single-engine Lysander airplanes flown on full moons by a group of iconoclastic buccaneers.

Fourcade was always on the run from the Gestapo or their German or French associates. She always traveled in disguise with false documents, shifting hair styles and colors, even wearing dental prosthetics. Through most of the war, she was separated from her two young children. For part of it she was pregnant with a third. And she was arrested, and escaped her captors, not once but twice.

Indeed, the Houdini-like escapes of Alliance stalwarts — squeezing between cell bars, smashing through windows, lowering themselves from fortresses and buildings by knotted sheets — become a leitmotif in Olson’s narrative. Until they aren’t, and then the horror stories of German prisons, bullets to the brain, and death-camp gassings underline the grim stakes of these cat-and-mouse travails.

Consider the case of Jacques Stosskopf, who was, during the war, the most despised Frenchman in Brittany. The deputy chief of naval construction at the Lorient shipyard, the Alsace native spoke fluent French and German and was invaluable to the German admiral Karl Dönitz in building a submarine base. What Stosskopf’s countrymen didn’t know was that he was not a collaborator but a keenly effective double agent, conveying key Nazi maritime resource and planning information to the British via Alliance’s Sea Star branch. When his double dealings were revealed, he was executed by the Nazis in 1944. The French renamed the base at Lorient in his honor in 1946.

Or, again, there is the profile of Jeannie Rousseau who was hired by the German high command as an interpreter. She passed intelligence along to the British, the Germans figured it out, and they arrested her. They released her, however, when German officers argued that the guileless-looking young woman could never have betrayed them. The condition of her release was that she had to leave the coastal region of Dinard.

She did, heading to Paris and becoming chief staff person for a syndicate of French industrialists working with the German military command. Loosened up by drinks and her friendly demeanor, they gradually revealed the development of the V-1 and V-2 rocket program. The intelligence she gathered for the British led to an Allied attack on the rocket laboratory, production, and testing facilities that set the Nazi program back months. “Were the Germans able to perfect these new weapons six months earlier, it was likely that our invasion of Europe would have encountered enormous difficulties,” General Dwight D. Eisenhower later wrote, “and, in certain circumstances, would not have been possible.” Rousseau was captured twice and imprisoned in three concentration camps, but she survived and lived to be 98 years old.

Finally, there is Olson’s portrait of Robert Douin. A flamboyant artist in Caen, eight miles inland from the Channel coast, he led a team of 40, including fishermen, teachers, shop owners, a blacksmith, and Douin’s own 14-year-old son, Remy, to create a 55-foot-long map that Douin delivered to Alliance in early March 1944.

It showed every German gun emplacement, fortification, and beach obstacle along the coast, together with details of German army units and their movements. As one military historian wrote, Douin’s masterpiece was “the most complete, detailed military picture of the landing sites” that the Allied command would be given in the course of the war.

Soon after, the Nazis shot Douin and his group in a German prison yard.

Who answers the calling to resist? M. R. D. Foot, the British authority on European resistance movements in World War II, observed, “resisters shared one characteristic besides bravery: contrariness. They were disputatious, argumentative, nonconformist, did not enjoy being ordered about.” Resistance was, for them, more reflex than conscious decision. But what kind of reflex? Moral? Religious? Ideological?

Asked why she risked her life to fight the Nazis, Jeannie Rousseau replied: “I don’t understand the question. It was a moral obligation to do what you are capable of doing. It was a must. How could you not do it?”

“Resistance,” Rousseau said, “is a state of mind. We can exercise it at any moment.”

When Fourcade died in 1989 at the age of 79, she was the first woman to be buried at Les Invalides, the monumental Parisian site dedicated to French military history and glory. Olson’s gripping account of Fourcade’s heroism honors her further.

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Alexander C. Kafka is a journalist and photographer in Bethesda, Maryland.