Leland bunked one night with engineers, who loved his dogs without self-consciousness. They had never been mistaken for marines or front line trenchmen. No one could drink so little as an engineer and yet get so drunk. “We’re efficient,” one of them explained at the local estaminet, where they took Lee for battery casings of beer. They managed to order without looking their server, an Alsatian girl, in the eye.

“Three fifty, three seventy-five, tops,” whispered an engineer.

“No, five hundred and five at least,” declared another.

“Do I have to explain the concept?” demanded the first.

Lee squinted at them. “What?”

Never a group to bless women with actual conversation, the engineers instead gazed across file rooms and city streets with hypnotized longing through their thick and smeared and rimless spectacles. Seeing a painfully diverse group of nurses and Salvation Army volunteers and journalists and French girls, they came up with a unit of measurement by which to discuss beauty. It was the millihelen. This was the amount of beauty it took to launch one ship.

The measurement worked through the visible spectrum from infrared (the American Quaker volunteers), to missionaries, then army nurses, Red Cross nurses, and then dieticians and cooks, journalists, heiresses who took exciting tours of the front lines, then up around the ultraviolet range came chauffeuses, for in a country where gasoline was scarce, a service-station owner would fill a tank only for the most attractive woman.

The most beautiful women in France, women literally beyond the visible spectrum, were the AT&T-trained Women’s Telephone Unit, a 233-member division of the Army Signal Corps. Their job was to run the old-fashioned magneto switchboards of France.

It was amazing to the average doughboy that when you called in coordinates from the front lines, you picked up a telephone receiver and, with explosions and mud around you, you could hear an American girl’s voice. This made her “Hello” as dazzling a presence in your ear as the breath of Aphrodite. They were known as “Hello Girls.”

And then, one day, they were gone. With the end of the war, the systems were staffed by men. The empty sheds in which they’d served were quickly overrun with spiders and mice, yet men still walked toward them hesitantly and knocked, hoping to be greeted with a female hello.

In May 1919, Leland’s papers came through, and he began the trip across France in a 40 & 8 troop train, so named because each car was designed for forty men or eight horses—meaning that the accommodations were hay bales, blankets, and body lice. The train lurched at a walking pace from station to station, doors on each side open for ventilation. Men tended to lean through the frame, watching the countryside, where families and their wagons of belongings were returning home.