A career analyst himself, Mr. McLaughlin said that some operations veterans “may feel angst” about the reorganization that will group them with analysts, but that it made sense. “The role of the analyst who puts all the pieces together has become more critical, because there are just more pieces,” he said.

After Sept. 11, the C.I.A. lent the F.B.I. some 40 analysts to try to jump-start the bureau’s reorientation, Mr. McLaughlin said. Before 2001, according to the national 9/11 commission, 66 percent of F.B.I. analysts were “not qualified to perform analytical duties.” Secretaries were sometimes rewarded with a promotion to analyst, with duties that included emptying the trash.

Proud special agents did not always see the value of analysts who did not necessarily build criminal cases — the traditional measure of success at the F.B.I. “At the end of my career, there was low-level tension between the agents and the analysts,” said Jack Cloonan, an F.B.I. agent from 1976 to 2002. “Who was running the case?”

Mr. Cloonan said the analysts did not always share the “camaraderie and esprit de corps” that agents had with one another. “Street agents are street agents,” he said, adding that he still heard grumbling from former bureau colleagues about some analysts who earn more than they do.

Philip Mudd, a career C.I.A. analyst who moved to a top counterterrorism job at the F.B.I. in 2005, said the difference in cultures was striking, and predictable. He recalled the case of David C. Headley, an American affiliated with Lashkar-e-Taiba, a Pakistani extremist group, who admitted to scouting targets for the 2008 terrorist attacks in Mumbai, India. Mr. Headley was arrested, prosecuted and sentenced to 35 years. The more difficult and novel task that the F.B.I. faced, and one for which analysts were critical, was determining whether Lashkar-e-Taiba had other operatives in the United States.

“It’s exploring the world of the unknown,” Mr. Mudd said.

By empowering analysts, “You’re telling agents, ‘You’re going to have to give up some turf,’ ” he said. “Someone’s going to say, ‘O.K., how many child molesters do you want me not to prosecute so you can do your analysis?’ ”