Annie was nineteen. Trees was sixteen. And Truus—though in the family they often called her by her full name, Truus Menger-Oversteegen—was only fourteen years old when the Germans occupied the Netherlands on May 10, 1940. Three sisters, all still teenagers, who within two years would be carrying out executions in the Dutch resistance.

It began, as these things often do, with small acts of defiance. The girls were young, and young women were not usually suspected of underground work. The Germans and their Dutch collaborators tended to look past them. That was exactly the point.

Their handler, a man named Hannie Schaft’s contact in the resistance, understood that a girl on a bicycle drew far less attention than a man with a weapon. And so the sisters were drawn into the armed resistance, part of a cell that carried out liquidations. The targets were not always Germans. In fact, many of them were Dutch.

The resistance considered the collaborators the greatest danger, because they knew the local people, the hiding places, the networks. A German officer could be spotted and avoided, but a Dutch informer could betray an entire cell within days. So the resistance began eliminating them, and the Oversteegen sisters became part of that work. Somewhere in 1942, the executions began.

Annie and Truus and Trees were given names, locations, and instructions. They would ride their bicycles to a meeting point, or wait in a park, or follow a target through the streets of Haarlem. Their youth was their disguise. Who would suspect a teenage girl on a bike of being an assassin?

Truus remembered one operation in particular. It involved a woman who had been collecting the names of every Jewish person in Haarlem, intending to hand the list over to the Sicherheitsdienst—the German security service. Such a list, in the wrong hands, meant deportation and death for every name on it. The resistance could not allow that list to be delivered.

So Truus’s mother, who was also involved in the resistance, approached the woman. Truus believed her mother was around fifteen or sixteen at the time—no, wait, Truus herself was that age; her mother was older. The details blur together in memory, but the confrontation was clear enough. The woman was confronted, likely in a park, and she was killed.

The list never reached the Germans. The methods were practical rather than romantic. The resistance needed the targets to come willingly, or at least unsuspectingly. The idea was that a young girl could lure a man somewhere quiet.

But Truus was frank about how little seduction was actually involved. Most of the victims were shot on the street, or in a park, or wherever they were met. They had bicycles. The girls would ride up, or meet the target, and then it was over quickly.

There was no time for elaborate ruses. If a target tried to kiss one of them, the operation was already done. That kind of thing only happened in the woods, and even then, it was rare. Most victims were shot the moment they arrived.

The girls would get back on their bicycles and ride away. Truus made it clear that she and her sisters were not seductresses. They were not femmes fatales. They were teenagers doing a job that no one else could do, because no one else could get close enough.

The war never really ended for them. It followed them for the rest of their lives. Truus remembered being very small—around eight years old—when she first saw Hannie Schaft’s name. It was in a history book, a schoolbook, with a picture of a girl with red hair.

Truus’s mother was reading it, and she began to cry. Truus asked what was wrong, and her mother said that Hannie had been a friend of hers. She had known her during the war, and Hannie had been murdered by the Germans. Hannie Schaft.

The girl with the red hair. The most famous female resistance fighter in the Netherlands, captured and executed by the Germans in April 1945, just weeks before the country was liberated. She and the Oversteegen sisters had worked together, been part of the same cells, carried out the same kind of jobs. Truus carried that grief her whole life.

The war came back to her again and again, and every time it did, Hannie Schaft came with it. Her mother had survived, but she never stopped mourning her friend. And Truus herself, who had done so much, who had killed and risked everything, spent the rest of her life trying to make sure it never happened again. The fear, the loss, the guilt—they were all mixed up together.

Truus and Hannie had been almost the same age. Both were strong women. But only one of them survived the war. There is a monument in the Netherlands, in a small town called Schoonhoven, dedicated to these women.

Truus’s own story, and that of her sisters, has been told in a book. The title of the book is: Then Never Again. That phrase, Truus believed, carried what she had really wanted all along. Not revenge, not glory, not recognition.

Just the simple, desperate hope that war would never return. That no more teenage girls would have to learn to kill. That no more mothers would have to bury their daughters. That no more friends would have to be executed in a field with their bodies left for the Germans to find.

She had wanted the world to be better. She had wanted it to be more beautiful. And after it was over, after she had done everything she could, the only thing left to say was: never again.