By Mark Mazzetti
The deaths of seven Central Intelligence Agency operatives at a remote base in the mountains of Afghanistan are a pointed example of the civilian spy agency's transformation in recent years into a paramilitary organization at the vanguard of America's far-flung wars.
Even as the C.I.A. expands its role in Afghanistan, it is also playing a greater role in quasi-military operations elsewhere, using drone aircraft to launch a steady barrage of missile strikes in Pakistan and sending more operatives to Yemen to assist local officials in their attempts to roll back Al Qaeda's momentum in that country.
The C.I.A. operatives stationed at Forward Operating Base Chapman in Khost Province, where Wednesday's suicide bombing occurred, were responsible for collecting information about militant networks in Afghanistan and Pakistan and plotting missions to kill the networks' top leaders. In recent months, American officials said, C.I.A. officers at the base had begun an aggressive campaign against a radical group run by Sirajuddin Haqqani, which has claimed responsibility for the deaths of dozens of American troops.
Over the past year, the C.I.A. has built up an archipelago of firebases in southern and eastern Afghanistan, moving agency operatives out of the embassy in Kabul and closer to their targets.
But the push to the front lines carries great risk.
In 1983 in Beirut, it took a car bomb loaded with 2,000 pounds of explosives to kill eight C.I.A. officers stationed at the heavily fortified American Embassy in the city. In Khost on Wednesday, all it took was one man bent on martyrdom to slip into a remote base and inflict a similar toll on the spy agency's relatively small work force.
Among those killed, officials said, was the chief of the Khost base, who was a mother of three and a veteran of the agency's clandestine branch. Besides the seven C.I.A. operatives who died, the blast also wounded six agency employees, according to a C.I.A. statement.
Current and former intelligence officials said Thursday that early evidence indicated that the bomber, in Afghan military fatigues, might have been taken onto the base as a possible informant and might not have been subjected to rigorous screening. But details about the episode remained murky, and a NATO official said the bomber had managed to elude security and reach an area near the base's gym.
C.I.A. personnel regularly take foreign agents onto the base before sending them on intelligence collection missions in eastern Afghanistan and across the border into Pakistan, said one Pentagon consultant who works closely with the C.I.A. in Afghanistan.
"You must to some degree make yourself known to people you don't trust," said one American intelligence official who, like others interviewed for this article, spoke anonymously to discuss classified information.
The bomber appears to have worn an explosives-laden suicide vest under an Afghan National Army uniform, two NATO officials said Thursday. The attack happened close to dusk, when some people at the base were relaxing before dinner.
In a statement to the C.I.A.'s work force, President Obama said that the spy agency had been "tested as never before," and that C.I.A. operatives had "served on the front lines in directly confronting the dangers of the 21st century."
Forward Operating Base Chapman sits in an isolated spot several miles from the town of Khost, but not far from Camp Salerno, a larger base used by Special Operations troops.
American officials said that the C.I.A. base had been a focal point for counterterrorism operations against the Haqqani network, a particularly lethal militant group that operates on both sides of the Afghan border.
"Those guys have recently been on a big Haqqani binge," said the Pentagon consultant. "I would be really shocked if the bombing on Wednesday wasn't some kind of retaliation."
There was an air of defiance among intelligence officials on the day after the attack, and some spoke of their fallen comrades using military language.
"There is no pullout," the American intelligence official said. "There is no withdrawal or anything like that planned."
The C.I.A. has always had a paramilitary branch known as the Special Activities Division, which secretly engaged in the kinds of operations more routinely carried out by Special Operations troops. But the branch was a small - and seldom used - part of its operations.
That changed after Sept. 11, 2001, when President George W. Bush gave the agency expanded authority to capture or kill Qaeda operatives around the world. Since then, Washington has relied much more on the Special Activities Division because battling suspected terrorists does not involve fighting other armies. Rather, it involves secretly moving in and out of countries like Pakistan and Somalia where the American military is not legally allowed to operate.
The fact that the agency is in effect running a war in Pakistan is the culmination of one of the most significant shifts in the C.I.A.'s history. But the agency has at times struggled with this new role. It established a network of secret overseas jails where terrorist suspects were subjected to brutal interrogation techniques, and it set up an assassination program that at one point was outsourced to employees of a private security company, then known as Blackwater USA.
Some longtime agency officers bristled at what they saw as the militarization of the C.I.A., worrying that it was straying too far from its historical missions of espionage and intelligence analysis.
When he took office in January, President Obama scaled back the C.I.A.'s counterterrorism mission, but only to a point. He ordered that C.I.A. prisons be shut and that C.I.A officers no longer play a role in interrogating suspects accused of terrorist acts.
At the same time, the administration has accelerated the C.I.A.'s drone campaign, using Predator and Reaper aircraft to launch missiles and rockets against militants in Pakistan.
In early 2009, the White House approved a C.I.A. plan to expand the drone operations in Pakistan into Baluchistan, where top leaders of Afghanistan's Taliban militia are thought to be hiding. The agency has also recently begun sending more operatives into Pakistan to, among other things, gather target intelligence for the drone program.
