Boko Haram: Inside Nigeria’s Unholy War by Mike Smith I.B. Tauris, 233 pp., $29.00

In early May, during the final days of the hot, dry season, I flew to Yola, the capital of Adamawa State in eastern Nigeria and an apparent safe haven from the Boko Haram insurgency. Over the past year, the radical Islamic fighters had taken over large swaths of territory in three northeastern Nigerian states, killing thousands, conscripting many young men, and kidnapping and raping young women and girls. But after a series of defeats at the hands of the insurgents, the Nigerian army had begun pushing them back. It had just liberated hundreds of women and children from captivity in the Sambisa Forest, a 23,000-square-mile reserve of savannah and near-impenetrable bush in neighboring Borno State, where many of the Boko Haram fighters had taken refuge. The army had trucked 275 freed hostages to a displaced persons’ camp—an abandoned training school for nomads—on the outskirts of Yola.

John Medugu, a social worker, led me through a yellow-concrete classroom building and into a shadeless courtyard. Dozens of women, children, and babies sat in the 100-degree heat, eating boiled yams for breakfast. Most of the children looked malnourished. The captives had endured harsh conditions in the bush, huddled beneath shade trees to escape the fierce sun, eating at best two meager meals of corn or watery bean soup a day, sleeping on the ground, forced to walk through the night to stay one step ahead of the Nigerian army.

During these marches, they had sometimes gone twenty-four hours without food or water. Christian women who had agreed to convert to Islam, as well as those who married Boko Haram fighters, had received preferential treatment from their captors. The fighters appeared to have used systematic rape as a means of controlling and humiliating their captives. They also, Medugu said, want to ensure the rise of another generation of Islamic jihadists. Thirty of the roughly ninety women aged eighteen and older, he told me, were pregnant.

One twenty-six-year-old woman I talked to came from a village near Chibok, the site of the girls’ secondary school from which 276 students had been abducted by Boko Haram a year before—one of the group’s most notorious crimes. (None of the Chibok girls was among those who had been rescued.) Her husband had disappeared during the Boko Haram attack on her village in April 2014, she told me, and she had been taken to the forest with her two children, ten and seven years old. When Nigerian troops had overrun the camp at eleven o’clock in the morning five days earlier, they started shooting at the retreating terrorists, and several women had been struck by bullets and died on the spot. Armored vehicles had crushed others to death. The insurgents had carried off both of her children. “They are worthless people,”…