A Ni­ger­ian Defense Ministry spokesman, Brig. Gen. Rabe Abubakar, defended the performance, saying that security was the first priority of the armed forces.

“We had to get that right before we started providing for these people. Nobody predicted this kind of situation would exist,” he said.

But aid workers acknowledge that they only belatedly realized that the crisis had outstripped the government’s ability to respond.

“Progress was far too slow in jointly recognizing the enormity of the situation,” said Simon Taylor, the deputy head of the U.N. Office for the Coordination of Humanitarian Affairs (OCHA) in Nigeria.

“Initially there was a sense that it could be handled by the state authorities,” said another U.N. official, who spoke on the condition of anonymity for diplomatic reasons. “It was only in April when we realized the magnitude, and the fact the government couldn’t handle this alone.”

When aid groups did start to get access to some cities in Borno this past summer, they were shocked by what they found. People were eating grass and locusts. The rates of severe acute malnutrition — a life-threatening lack of food — were among the highest in the world. About half of all children were malnourished. In August, two children were found paralyzed by polio after eradication campaigns were cut back because of insecurity. They were the first recorded polio cases in Africa in almost two years.

Yet even now, after the crisis has been acknowledged, many people in “accessible” areas where food aid is meant to be arriving are going hungry. In some cases, humanitarian groups say they are still trying to determine where the needs are.