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In late 1942, England, still standing alone in Western Europe, was strategizing how to free Nazi-occupied France.

On a night in September lit by the full moon, two young women, Lise de Baissac and Andree Borrel, parachuted out of a low-flying airplane into the French countryside. The women would carry out a top secret mission: setting up safe houses and channeling airdropped weapons to arm the nascent resistance.

They were part of a program by the Special Operations Executive, a group set up in 1940 outside of military command, to "set Europe ablaze," in the words of Winston Churchill.

Sarah Rose tells their story in "D-Day Girls," a meticulously crafted new book.

It had been decided that there needed to be an Allied invasion of France to force Hitler to fight a two-front war. That invasion was eventually called D-Day, and it took place in June of 1944.

The F Section, standing for French Section, recruited women because there was a shortage of manpower. There was only one problem: Women had never been behind enemy lines before. But Churchill gave his blessing.

Recruits had to be British citizens who could speak perfect French, who could "act French" and blend in with the natives. F Section women came about this qualification in a number of ways; some were originally French citizens who married a Brit, gaining citizenship that way; de Baissac was raised in Mauritius, a French-speaking British colony.

Once deployed to France, they watched and waited — for meetups with other agents, for airdrops of weapons, for coded messages that could be heard at the end of the BBC's French-speaking broadcasts. A nonsense saying such as "The dog sneezed on the curtains" at the end of the broadcast could mean an important message for their mission.

Weapons and agents were parachuted in at every full moon, and women such as Borrel found themselves tasked with teaching French teenagers how to use the plastic explosives.

As the war slogged on through 1943 and D-Day approached, tension was high as resistance attacks increased. Nazis moved in on British intelligence. Agents were captured, and entire networks compromised.

Spies, including women from the F Section, were rounded up, interrogated, tortured, jailed and put in concentration camps, including Borrel, who was executed at Natzweiler-Struthof at age 24. Her lover, another Allied spy, cracked under questioning.

After D-Day, France was free by the end of 1944, but not all of the F Section survived. Thirty-nine of them went to war, and 13 died in action.

Besides giving an overview of the war and how the women of the F Section fit into it, Rose gives a granular view of what it was like to be an agent on the ground — such as how lonely secret agent life can be, stationed in unknown cities under a false name, waiting for instructions. Or falling in love with male spies they were sometimes paired with.

Rose also highlighted the inequalities the women faced postwar, most notably when it came time for the secret spies to be recognized for their service.

Many F Section agents, including de Baissac, received the Most Excellent Order of the British Empire (Civil). Male agents, however, who did the same tasks as the female agents received more prestigious awards such as the Victoria Cross, which honored military valor.

Ultimately, the laurels are beside the point; the record stands that this small but fierce coalition of women did something quite extraordinary. Against all odds, they helped France liberate itself.

Sheila McClear is a freelance writer. She is the author of "The Last of the Live Nude Girls."

D-Day Girls
By: Sarah Rose.
Crown, 384 pages, $28.