As Gen. David Petraeus shifts from the Afghan battlefield to run the CIA, he leaves behind a legacy of tactical and spycraft changes that spurred more killings and captures of Afghan militants while reducing insurgent attacks to their lowest level in years, senior U.S. officials in Afghanistan said.

From April to July this year, officials said, 2,832 special operations raids led to the capture of 2,941 insurgents and the killings of 834. That's twice the number captured or killed during the same period a year ago, when special operations forces captured more than 1,350 insurgents and killed 1,031 in roughly the same number of raids, according to figures shared with The Associated Press by NATO headquarters.

No one claims the latest numbers guarantee long-term success in keeping the anti-government Taliban factions from reconstituting or in driving mid-level Taliban to the negotiating table. Petraeus warned as he left his post that the gains are fragile, as shown by a series of recent high-profile Taliban assassinations and attacks.

But the system Petraeus helped institutionalize _ a fusion of intelligence, U.S. law enforcement and special operations hunter-killer teams _ is operating at a higher pace and level of synchronization than in any previous year, and is expected to remain a key component, even as conventional forces draw down. Petraeus shares credit for what U.S. officials call a turnaround in Afghanistan with his predecessor, retired Gen. Stanley McChrystal.

The continued raids are intended to pressure mid- and lower-level Taliban to reintegrate with Afghan society, and buy time for the Afghans to step into the breach left by departing U.S. troops, senior administration officials say, speaking on condition of anonymity to discuss strategic matters.

That picture of Petraeus, as precision-killer-commander, is somewhat at odds with the familiar portrayal of the four-star military champion of "soft power" counterinsurgency in Iraq and Afghanistan _ using the army's might to first take territory, but then to help foster nation building.

But many who have worked for him said Petraeus has always been a keen proponent of accurately killing the enemy. Petraeus frequently complains that political leaders, and the media, fail to understand that counterterrorism _ tracking and killing the enemy _ is a subset of counterinsurgency.

There is even some mild concern in intelligence circles that Petraeus is so comfortable with the targeting side of the counterterrorism equation that, in his new CIA role, his kill-capture strategy may take precedence over the long-term surveillance and slow, painstaking, gumshoe-style work that is the bread and butter of the spy world.

In his last weeks in command in Afghanistan, Petraeus pointed out that the military's increased kill-and-capture pressure on the Taliban had driven enemy-initiated violent attacks down 14 percent lower this July than last July. Also, violence is lower than during the same two-month period a year ago -- something officials say they have not seen since 2006.

That positive assessment stands in contrast to a recent U.N report that found the number of Afghan civilians killed in war-related violence rose 15 percent in the first half of this year. The number of suicide attacks remained steady with last year, but the number of civilians killed by them soared by 52 percent, the report said.

Airstrikes conducted by the U.S.-led coalition _ another area of targeting that surged under Petraeus _ remained the leading cause of civilian deaths by pro-government forces.

But U.S. officials say the trends remain positive. They explain away high-profile attacks like the recent killing of President Hamid Karzai's half-brother, CIA ally Ahmed Wali Karzai, as spectacular attempts to draw attention or simply score-settling among Afghan power rivals.

They said the lower violence overall is attributed to the lack of expertise of Taliban leaders who have replaced those removed over the past year. One trend shows that some 2,000 Taliban foot soldiers also gave up their arms over the past year, said a senior NATO official, speaking on condition of anonymity to discuss the trend.

Senior officials in Kabul said the surge in precision operations is due to a system called counter-network, designed by McChrystal in Iraq, when he commanded the military's elite counterterrorism unit, the Joint Special Operations Command. It brings together military special operations, U.S. intelligence agencies and others to track, kill or capture militants and destroy their network faster than they can rebuild it. The idea is that the constant pressure will drive militants to negotiate or surrender.

A key tenet is a preference for capturing militants rather than killing them, where possible. That gives U.S. and Afghan authorities a chance to interrogate them, to find out everything from who controls the network to what drives insurgencies from valley to valley.

One of the first moves by NATO intelligence chief Brig. Gen. Steve Fogarty when he arrived last fall was to map the Taliban network, using intelligence derived from interrogation, blended with data gathered by U.S. military and Afghan intelligence operatives in the field, as well as electronic eavesdropping and video tracking.

"By the time a detainee gets to ... interrogation, we know who you're associated with, we know why you're doing this," said Vice Adm. Bob Harward, a Navy SEAL who ran the detainee operations for more than a year. Detainees' resistance often crumbles when they realize the interrogators already have a clear picture of their group or region, he said.

"The fundamental value in capturing the enemy is so that you have a better grasp of the environment," adds counterinsurgency proponent Brig. Gen. Michael Nagata, a contemporary of McChrystal's and the second in command at the U.S. Embassy's military office in Pakistan.

"The more you understand the environment, the more effective your choices will be," said Nagata, who works with the Pakistanis on their hunt for militants on their side of the border.

Sometimes, the choice is targeting the leaders, he said. Other times, it's buying them out of the insurgent business by offering them jobs, all the while buying time for local government to fix the problems that drove them to fight in the first place. Nagata added _ as Petraeus frequently expounds _ killing is only part of the equation.