After more than a year of civil war, the toll in Sudan is heartbreaking: thousands killed, millions scattered and cities besieged or destroyed across a vast nation three times as large as France. Much of the capital lies in rubble. This month, international officials declared that part of Sudan was in a famine. At least 100 people die of hunger every day.

And there are signs it could soon get much worse.

Recently, I spent three weeks in Sudan, traveling across a part of the world that few foreign reporters have reached. The scale and intensity of destruction were startling: A conflict that started as a power struggle between rival generals has metastasized into a far bigger and messier conflagration, threatening to spread chaos across an already fragile region.

Despite all that, the conflict has received scant attention from world leaders or money for humanitarian aid. But its soaring human cost is making it ever harder to ignore. U.N. experts warn that Sudan is again spiraling into genocidal violence, as it did in the early 2000s. Samantha Power, the head of USAID, says it is “the single largest humanitarian crisis on the planet.”

One faint glimmer of hope lies in tentative peace talks, mediated by the United States, that started in Switzerland yesterday. Today’s newsletter explains the stakes: how an unexpected civil war is crushing Africa’s third-largest country — and what could stop the suffering.

Only five years ago, Sudan was the source of euphoric hopes, when crowds of young people gathered to oust President Omar Hassan al-Bashir, the country’s dictator of three decades. For once, it seemed that a popular revolution in an Arab country might succeed.