Micheline Dumont-Ugeux, second from left, along with fellow Belgians Andree de Jongh, left, and Elvire de Greef, visit the Ministry of Defense in London as guests of the Royal Air Forces Escaping Society on Jan. 6, 1967. The three were awarded the George Medal for helping Royal Air Forces troops escape from occupied Europe during World War II. They are pictured talking to Group Captain Bill Randle, second from right, and Air Commodore Denis Crowley-Milling, whom they had helped to escape. (Bob Thomas/Bob Thomas/Getty Images)

Micheline Dumont-Ugeux, a major figure in the Belgian underground resistance during World War II who helped hundreds of Allied troops evade capture by Nazi forces as they sneaked across mountaintops and international borders, died Nov. 16 at her home in Saint-Siffret, France. She was 96.

Her death was announced by a funeral home in Uzes, France. The cause was not disclosed.

Mrs. Dumont-Ugeux joined the Belgian resistance in 1942, the same year her parents and sister were arrested by the German Gestapo for their underground work against Nazi occupiers of their homeland.

Known by her code name of Lily, she spent three years, often at great risk, as a leader of a secret organization known as the Comet Line. The clandestine escape network rescued at least 750 Allied airmen whose planes had been shot down over Europe and enabled the men to escape across Belgium, France and Spain.

Mrs. Dumont-Ugeux personally helped at least 250 of them, including many Americans, reach freedom, often outwitting Nazi agents at every step of the way. The Comet Line was one of the most successful resistance efforts of the war. Many of the group’s leaders were women.

In her early 20s at the time, Mrs. Dumont-Ugeux was barely five feet tall and carried false identity papers, shaving six years off her age.

“Her face was round and artless,” British intelligence officer Airey Neave later wrote in a book about her. “She looked no more than 15, an advantage that she used to the full.”

Soon after she joined the Comet Line, Mrs. Dumont-Ugeux was partly in charge of logistics in Brussels, “organizing safe houses, working with photographers to produce identity cards and, most important, leading airmen on the way from the countryside to the French border,” former Washington Post journalist Peter Eisner wrote in his 2004 book, “The Freedom Line.”

Trained as a nurse, she helped airmen recover from their wounds, and also taught them French phrases and European manners.

“Keep your hands out of your pockets,” she advised, after seeing Americans casually jangle their pocket change as they walked along. “No European does that.”

She told Americans how to smoke cigarettes in the European style, to avoid being detected, and how to wear a beret. She warned them never to switch their knife and fork from one hand to the other while eating.

At times, if Gestapo agents were lurking nearby, she would embrace an airman she barely knew and appear to be locked in a passionate kiss.

In 1943, Mrs. Dumont-Ugeux spent six weeks helping Robert Z. Grimes of Portsmouth, Va., a B-17 pilot, recover from a leg wound after he was shot down over rural Belgium. She found a doctor who extracted a two-inch piece of shrapnel without anesthesia, as Grimes held a towel between his teeth.

When one of her underground colleagues was arrested, Mrs. Dumont-Ugeux moved quickly to take Grimes to a different safe house, directing other members of the Comet Line to clear out all the men’s clothing, razors and other telltale evidence from the previous house.

After Grimes had recovered enough to walk without assistance, Mrs. Dumont-Ugeux handed him over to other resistance fighters, who took him across the French border, then to Paris and on to the Basque region. Two days before Christmas, Grimes forded a river in the middle of the night, even as another American airman walking behind him lost his footing and drowned.

Mrs. Dumont-Ugeux had to be on constant alert for Nazi spies seeking to infiltrate her group. Despite precautions, dozens of members of the Comet Line were arrested or executed, and many Allied aviators were caught and sent to prison camps.

The Gestapo knew of Mrs. Dumont-Ugeux’s identity, but she spent only two days in custody, in 1944. She was released because her interrogator assumed that she was too young to be a threat.

One time, she unmasked a Nazi agent posing as an English-speaking pilot by asking questions using American slang — which left the collaborator speechless. In 1944, while she was working for the resistance in Paris, she realized that Jean Masson, a trusted member of the Comet Line, was a double agent working for the Gestapo.

She followed him around Paris, confirming her suspicions. Then Masson noticed Mrs. Dumont-Ugeux and began to walk toward her.

“When she looked back, he was following, ever faster,” Eisner wrote in his book. “When Lily reached” a Metro station, “she bounded down the stairs and out of sight, skidding around the rounded corners of the tunnel. . . . As she vaulted around each level and down into the subway, she knew Masson was still following her.”

She blended into the crowd and boarded a subway train, crouching low.

“As the car doors closed and the train pulled out of the station,” Eisner wrote, “Jean Masson was turning in circles, glimpsing faces in the windows and on the platform, but he was unable to see Lily.”

Mrs. Dumont-Ugeux fled Paris and crossed the Pyrenees Mountains on foot before reaching Madrid. She received an officer’s commission in the British army and returned to Brussels for the rest of the war.

A resistance assassin was assigned to kill Masson, but he shot another man instead. Masson was later arrested and was executed after the war.

Aline Micheline Dumont was born May 20, 1921, in Brussels. She spent much of her childhood in the Belgian Congo (now Congo), where her father was a doctor.

After her family members were arrested in 1942, Mrs. Dumont-Ugeux tried to visit them in prison, only to be told, “These are not your parents. We arrested the entire family.”

Her father died in a German prison camp in 1945.

That year, she married another resistance fighter, Pierre Ugeux, who later became director of the Belgian public power utility. He died in 2009.

Survivors include three children.

After the war, Mrs. Dumont-Ugeux helped found a group of former Comet Line agents and organized a trip to the United States and Canada, where they met aviators they had rescued. Grimes, who spent 30 years as an Air Force officer and later became a public school administrator in Prince William County, died in 2010.

Britain awarded Mrs. Dumont-Ugeux the George Medal, which is presented to people who demonstrated “acts of great bravery” in noncombat roles during the war. A British document, once marked Top Secret, praised her heroism with the Comet Line.

“Her name became a legend amongst the countless airmen who had been shepherded across Brussels by the famous Lily,” it noted. “Mlle. Dumont pursued those ideals of patriotism and duty with unflinching determination, fearing nothing and ready to sacrifice all, with the result that through her gallantry and devotion countless airmen were able to escape from the enemy.”