American officials said that one of the biggest challenges facing the C.I.A. is to take a large group of case officers who have spent more than a decade trying to hunt terrorists in war zones and retrain them to spy in countries like Russia, China and other so-called hard targets — difficult environments where governments are hard to penetrate and many C.I.A. operatives are under constant surveillance. Spying on the streets of Moscow might involve less physical danger than working in Karachi, Pakistan, or in Sana, Yemen, but trying to recruit Russian sources and to outwit Russian intelligence officers requires a subtlety that spies have not always practiced in Iraq and Afghanistan.

In an embarrassing case last week, the Russians detained a young man in Moscow who they said was a C.I.A. officer trying to recruit a Russian official to spy for the United States. Video images of the man, Ryan Fogle, showed him wearing a shaggy blond wig under a baseball cap and revealed an assortment of items he was said to be carrying — including a compass, a street map of Moscow and a second wig. The images portraying an amateurish American spying effort played in an endless loop on Russian television.

Beyond the drone campaign, the C.I.A. over the past decade built large stations in Kabul and Baghdad, populating them with hundreds of young clandestine officers, many of whom were serving on their first overseas tour. The way C.I.A. officers operate in war zones — hunkered down much of the time behind large concrete walls and driving through cities in armored vehicles — is often the antithesis of the tradecraft used in noncombat areas, where spies need to blend into the local population.

Mr. Brennan, who spent decades in the C.I.A. as an intelligence analyst, also faces a significant challenge in widening the aperture of the CIA’s analytical work — which has also been consumed by the counterterrorism mission since the Sept. 11 attacks.

“A lot of things that pass for analysis right now is really targeting,” said Michael V. Hayden, a former C.I.A. director. “There has to be a shift in emphasis.”

In 2011, as popular revolutions spread through the Arab world, White House officials were critical of C.I.A. analysts for what they saw as a failure to keep up with the rapidly changing dynamics of the revolts. During his confirmation hearing earlier this year, Mr. Brennan made a veiled reference to this criticism.

“With billions of dollars invested in C.I.A. over the past decade, policymaker expectations of C.I.A.’s ability to anticipate major geopolitical events should be high,” he said in a written response to questions posed by the Senate Intelligence Committee. “Recent events in the Arab world, however, indicate that C.I.A. needs to improve its capabilities and its performance still further.”