"We moved all over the city, and we would not sleep in the same place two nights in a row," Maguire said.

In Iraq in 2014, by contrast, CIA officers have been largely hunkered down in their heavily fortified Baghdad compound since U.S. troops left the country in 2011, current and former officials say, allowing a once-rich network of intelligence sources to wither. Maguire and other current and former U.S. officials say the intelligence pullback is a big reason the U.S. was caught flat-footed by the recent offensive by a Sunni-backed al-Qaida-inspired group that has seized a large swath of Iraq.

Iraq is emblematic, they say, of how a security-conscious CIA is finding it difficult to spy aggressively in dangerous environments without military protection. Intelligence blind spots have left the U.S. behind the curve on fast-moving world events, they say, whether it's disintegration in Iraq, Russia's move into Crimea or the collapse of several governments during the Arab Spring.