YOLA, Nigeria -- Hadiza Ibrahim knew for sure that Boko Haram had taken over her town when she was going to get water and saw the bodies of two men on the ground. Their throats had been cut.

“It was horrible,” she says. At the time, she was carrying her young son on her back, so she shielded his face with her veil. “I couldn’t let him see that.”

Soon after Ibrahim stepped over the bodies, two Boko Haram men stopped her in the road, guns dangling at their sides, asking where her husband was. But he had already fled, and it was her they wanted.

“They both wanted to marry me. They said that, since he left, I was part of their property,” recalls Ibrahim, 22.

The terrifying incident, which happened in August, is not uncommon among women like her, who stay in their homes weeks or months after the militant group attacks and men flee for their lives. Locals know that Boko Haram tends to kill all men immediately and spare the women. They may manage to avoid death, but can’t escape other perils, chiefly the prospect of what Boko Haram fighters call “marriage,” but it is really a threat, not a proposal.

Ibrahim managed to avoid the fate of a sex slave by quickly thinking on the spot. “I insulted them,” she says. “Then I asked them how they would feel if some other man was talking to their wife or sister like this, and they left me alone.”

But not all women in northeastern Nigeria, where Boko Haram at one time controlled an area as large as Belgium, are as lucky as Ibrahim.

After the group kidnapped more than 200 girls from a school in the town of Chibok, Boko Haram released a video of its leader Abubakar Shekau telling viewers the children had been “married off” to militants. Some of them were as young as 13. None have been seen since.

According to Human Rights Watch, Boko Haram has abducted at least 500 women and girls during the past five years. In a recent report, the watchdog group documents how girls as young as 15 were promised to some militants as wives. In this context, so-called marriage can entail everything from forced hard labor to continued sexual abuse. Moreover, “the rape of women and girls abducted by Boko Haram has been underreported because of a culture of silence, stigma and shame around sexual abuse in Nigeria’s conservative North,” the report says.

This is one of the most nefarious tactics employed by terrorist groups, experts say.

“One way to recruit women is to sexually abuse them and give them nothing to live for,” says Mia Bloom, a terrorism expert at the Center for Terrorism and Security Studies at the University of Massachusetts Lowell. “In these societies, these women are damaged goods, they’re not marriageable after that.”

However, the fate of a woman facing Boko Haram often depends on which individuals she is dealing with, since the group is less of an organized religious militia than a haphazard gang of criminals. Some victims even enjoy a sort of perverse protection.

“Women and girls interviewed by Human Rights Watch said that some Boko Haram commanders appeared to make some effort to protect them from sexual violence,” the Human Rights Watch report says.

Ibrahim’s tale bears out the descriptions of Boko Haram as unpredictable. The militants are generally a fearsome and scary lot. “They move around town, like they’re on a patrol,” she says. “Sometimes they walk, sometimes they have a vehicle -- but they always have guns, some of them have two at once.” But she says that sometimes she wasn’t afraid of them, and some of the men were easygoing and relaxed -- even playing with some of the children. Others were far less endearing, and it was from these men that the marriage proposals generally came.

“Some of them are really tough. They speak loudly and make you very scared,” Ibrahim says, remembering how worried her family was when a Boko Haram member became very interested in her 18-year-old sister and wanted to marry her. Unsurprisingly, her sister wasn’t keen on the idea.

“She didn’t like them, but they kept coming to the house insisting she get married to them,” Ibrahim recalls. Eventually, the family managed to smuggle her out to a nearby town to stay with distant relatives. When the Boko Haram member couldn’t find her, he threatened to kill her mother if the family didn’t produce her.

“My mother said she would rather die than see her daughter married to them,” she says. Eventually, he just left the family alone.

Many of the displaced people now staying in temporary residences here in Yola have stories of close-up encounters with Boko Haram members.

Another woman recalls a time when she convinced one of them to let her go.

Although she doesn’t want to give her name for fear the group might still be looking for her, the woman recounts an incident a few weeks ago when she and about five other women were in a town after Boko Haram took over. One of the members loaded them and their children into a vehicle, telling them he would be taking them to a “new life” with the group in a city called Michka.

“He seemed a bit nicer. He offered us some food and drinks, trying to show us how good things would be,” she says. But the women knew this was not the place they wanted to be.

As they were driving, many of them pleaded with the driver, a clean-cut man in his 40s who appeared pretty well-educated, to let them go.

“One of the women asked whether he wanted her children to be orphans,” she says. “Another one told him how her husband was killed by Boko Haram and now she’s on her own, and another woman told him she needed to collect her children in a different village.”

Eventually, she says, they managed to wear him down. He dropped them off in the middle of a deserted road at 11 p.m. Together, they walked until 4 p.m. the next day to reach the nearest town, and later reconnected with their families at settlements for internally displaced persons. She credits herself and the other women with being persuasive, but she still says she’s lucky.

“With Boko Haram, you never know,” she says. “You never know what’s going to happen.”