Already this year, two severely malnourished local boys had been so withered that they were beyond saving. The doctor, Abdu Ali Saad, kept pictures of the boys, ages 2 and 4, on his phone: a reminder of the dangers facing children in Yemen’s long-neglected countryside, more forsaken these days than ever.

“This is every day,” Dr. Saad said, motioning to the parents waiting on a recent day, some who had walked hours on dusty roads to reach the clinic, and who looked hardly better off than their children.

“Malnutrition,” he added, “is an emergency.”

One million children younger than 5, roughly a third of the age group in Yemen, are suffering from life-threatening malnourishment, according to Daniela D’urso, the head of the European Commission’s humanitarian aid office in Yemen. About two million children are chronically malnourished. Nearly 60 percent of Yemeni children suffer from stunted growth, according to public health workers, who in the past few months have noticed other worrying trends, including cases of malnutrition giving rise to other maladies like tuberculosis.

The crisis is “unprecedented,” Ms. D’urso said.

Yemen’s humanitarian crises were “largely the result of failure of governance and mismanagement,” Mr. Benomar said.

“Getting out of the crisis,” he added, “is what would help.”

The scale of the crisis was apparent in the cramped home of Huda bin Nasser, a young mother in the village of Sheikhain, outside Taiz, in central Yemen. The family received its staples — eggs and milk — from a cow and a chicken that lived in the kitchen, but other types of food were a struggle. All of Ms. bin Nasser’s four children were malnourished, with her youngest, Hadiya, suffering severely and receiving treatment from the International Medical Corps volunteers.

East of Milah, in a valley in the district of Al Maqatirah, where 50,000 people live, the villages climb up the mountains, largely inaccessible except on foot. Symbols painted on many houses represented Yemen’s political parties, now in disarray. The paintings were signs of loyalty pledged by the residents here, with favors seldom returned.

In a clinic in the valley, Nada Abdullah, 22, watched as a doctor weighed her skinny 2-year-old boy, Abdul Rahman, whom she took to the clinic after he stopped eating. It had taken them five hours to get there.

Abdul Rahman was malnourished, hovering somewhere down the line toward a life-threatening condition. Ms. Abdullah said she knew what to feed the boy — her mother had taught her about a balanced diet that included fruits and vegetables — but her generation seemed somehow less able to care for its children than the last.

She recited a familiar list of luxuries, like chicken and fish, affordable once a week. During religious holidays, she said, they sometimes even bought red meat.