Even as the Obama administration scrambles to confront the Islamic State and a resurgent Taliban, an old enemy seems to be reappearing in Afghanistan: Qaeda training camps are sprouting up there, forcing the Pentagon and American intelligence agencies to assess whether they could again become a breeding ground for attacks on the United States.

Most of the handful of camps are not as big as those that Osama bin Laden built before the Sept. 11, 2001, attacks. But had they re-emerged several years ago, they would have rocketed to the top of potential threats presented to President Obama in his daily intelligence briefing. Now, they are just one of many — and perhaps, American officials say, not even the most urgent on the Pentagon’s list in Afghanistan.

The scope of Al Qaeda’s deadly resilience in Afghanistan appears to have caught American and Afghan officials by surprise. Until this fall, American officials had largely focused on targeting the last remaining senior Qaeda leaders hiding along Afghanistan’s rugged, mountainous border with Pakistan…

“I do worry about the rebirth of AQ in Afghanistan because of what their target list will be — us,” said Michael Morell, the deputy director of the C.I.A. until two years ago, whose book, “The Great War of Our Time,” recounts the efforts of the Bush and Obama administrations to destroy the Qaeda leadership.