The civil war in Congo is an ethnic conflict, but gender has become a crucial factor. Women are bearing the brunt of one of the horrible weapons used in the war: rape. CNN’s Anderson Cooper reports.

IN THE 19TH CENTURY, the paramount moral challenge was slavery. In the 20th century, it was totalitarianism. In this century, it is the brutality inflicted on so many women and girls around the globe: sex trafficking, acid attacks, bride burnings and mass rape.

Yet if the injustices that women in poor countries suffer are of paramount importance, in an economic and geopolitical sense the opportunity they represent is even greater. “Women hold up half the sky,” in the words of a Chinese saying, yet that’s mostly an aspiration: in a large slice of the world, girls are uneducated and women marginalized, and it’s not an accident that those same countries are disproportionately mired in poverty and riven by fundamentalism and chaos. There’s a growing recognition among  everyone from theWorld Bank to the U.S. military’s Joint Chiefs of Staff to aid organizations like CARE that focusing on women and girls is the most effective way to fight global poverty and extremism. That’s why foreign aid is increasingly directed to women. The world is awakening to a powerful truth: Women and girls aren’t the problem; they’re the solution.

One place to observe this alchemy of gender is in the muddy back alleys of Pakistan. In a slum outside the grand old city of Lahore, a woman named Saima Muhammad used to dissolve into tears every evening. A round-faced woman with thick black hair tucked into a head scarf, Saima had barely a rupee, and her deadbeat husband was unemployed and not particularly employable. He was frustrated and angry, and he coped by beating Saima each afternoon. Their house was falling apart, and Saima had to send her young daughter to live with an aunt, because there wasn’t enough food to go around.

“My sister-in-law made fun of me, saying, ‘You can’t even feed your children,’ ” recalled Saima when Nick met her two years ago on a trip to Pakistan. “My husband beat me up. My brother-in-law beat me up. I had an awful life.” Saima’s husband accumulated a debt of more than $3,000, and it seemed that these loans would hang over the family for generations. Then when Saima’s second child was born and turned out to be a girl as well, her mother-in-law, a harsh, blunt woman named Sharifa Bibi, raised the stakes.

“She’s not going to have a son,” Sharifa told Saima’s husband, in front of her. “So you should marry again. Take a second wife.” Saima was shattered and ran off sobbing. Another wife would leave even less money to feed and educate the children. And Saima herself would be marginalized in the household, cast off like an old sock. For days Saima walked around in a daze, her eyes red; the slightest incident would send her collapsing into hysterical tears.

It was at that point that Saima signed up with the Kashf Foundation, a Pakistani microfinance organization that lends tiny amounts of money to poor women to start businesses. Kashf is typical of microfinance institutions, in that it lends almost exclusively to women, in groups of 25. The women guarantee one another’s debts and meet every two weeks to make payments and discuss a social issue, like family planning or schooling for girls. A Pakistani woman is often forbidden to leave the house without her husband’s permission, but husbands tolerate these meetings because the women return with cash and investment ideas.

Saima took out a $65 loan and used the money to buy beads and cloth, which she transformed into beautiful embroidery that she then sold to merchants in the markets of Lahore. She used the profit to buy more beads and cloth, and soon she had an embroidery business and was earning a solid income — the only one in her household to do so. Saima took her elder daughter back from the aunt and began paying off her husband’s debt.

When merchants requested more embroidery than Saima could produce, she paid neighbors to assist her. Eventually 30 families were working for her, and she put her husband to work as well — “under my direction,” she explained with a twinkle in her eye. Saima became the tycoon of the neighborhood, and she was able to pay off her husband’s entire debt, keep her daughters in school, renovate the house, connect running water and buy a television.

“Now everyone comes to me to borrow money, the same ones who used to criticize me,” Saima said, beaming in satisfaction. “And the children of those who used to criticize me now come to my house to watch TV.”

Today, Saima is a bit plump and displays a gold nose ring as well as several other rings and bracelets on each wrist. She exudes self-confidence as she offers a grand tour of her home and work area, ostentatiously showing off the television and the new plumbing. She doesn’t even pretend to be subordinate to her husband. He spends his days mostly loafing around, occasionally helping with the work but always having to accept orders from his wife. He has become more impressed with females in general: Saima had a third child, also a girl, but now that’s not a problem. “Girls are just as good as boys,” he explained.

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Nicholas D. Kristof is a New York Times Op-Ed columnist and Sheryl WuDunn is a former Times correspondent who works in finance and philanthropy. This essay is adapted from their book “Half the Sky: Turning Oppression Into Opportunity for Women Worldwide,” which will be published next month by Alfred A. Knopf. You can learn more about “Half the Sky” at nytimes.com/ontheground