“It’s going to get a lot harder,” said Don Hepburn, a former senior C.I.A. officer who served in Afghanistan. “The agency is being drawn in many, many directions.”

Mr. Biden’s determination to end the military’s involvement in Afghanistan means that, starting next month, any American presence in the country would most likely be part of a clandestine operation that is not publicly acknowledged.

The C.I.A.’s new mission will be narrower, a senior intelligence official said. It no will longer have to help protect thousands of troops and diplomats and will focus instead on hunting terrorist groups that can attack beyond Afghanistan’s borders. But the rapid American exit devastated the agency’s networks, and spies will most likely have to rebuild them and manage sources from abroad, according to current and former officials.

The United States will also have to deal with troublesome partners like Pakistan, whose unmatched ability to play both sides of a fight frustrated generations of American leaders.