SABAGAI, Pakistan — From atop a craggy hillock, the silver-haired Lt. Col. Javed Baloch gestures toward a small black opening in a sandstone outcropping. It's the mouth of a cave.
Two minutes later a powerful explosion rattles the hillock, and a massive plume of grayish-white smoke rushes skyward.
Cave by cave, the Pakistani army is trying to blow up the underground labyrinth running from tribal areas toward the border with Afghanistan to keep militants away.
This is the front line of Pakistan's battle against militants on its own soil. The three-month-old offensive is the country's most aggressive effort to date, countering U.S. and Afghan charges that it is not doing enough to root out Taliban and al-Qaida fighters who crisscross the border. It is also the Pakistani military's first foray into the Bajur region, where militants are dug in and have in places set up a parallel administration.
An Associated Press team traveled with the Pakistani military deep into a tribal area late last month, almost to the Afghan border. The operation shows the army can put pressure on militants and even wrest some territory back from them, but it may never be able to drive them out from a rugged area of nooks and crannies. More militants are already sneaking in from Afghanistan as reinforcements, and U.S. troops in Afghanistan have installed 68 motion sensors along the border to try to detect them.
The battle is for Bajur, a key base and transit route for Arab and other foreign militants headed for Afghanistan. Here a CIA drone once targeted al-Qaida's No. 2, Ayman al-Zawahiri, without success.
Any progress, however, is now in danger from an unexpected front. The recent terrorist attack in Mumbai has raised the prospect that Pakistan might shift troops from its tribal regions to the border with India. Both sides want to avoid a confrontation, but emotions are running high.
In the meantime, the Pakistani army has used helicopter gunships and fighter jets to blast entire villages in Bajur to rubble, driving 250,000 tribesmen out of their homes and burying 82 of their own soldiers. Pakistan has battled militants in tribal areas before, but never with such intensity.
"I feel hurt. There is so much destruction. That is why always we are trying to prevent war, but we were left with no choice," Baloch says.
He bristles at any U.S. questioning of the will of Pakistani soldiers to fight the militants.
"Listen, I have picked up the bodies of my dead soldiers and carried them out. I haven't left a body behind. Do you think this is something we do without pain in our heart?" he asked. "I tell everyone who is saying we aren't doing enough, 'Send your brothers, your fathers, your uncles and I will take them into battle with me. I will show them.'"
The convoy of Pakistani soldiers rumbles out of Khar on a crisp morning, a slight mist hanging in the air.
It was from here, the capital of Bajur, that the army had launched its offensive on Sept. 8. Previously, only the ill-equipped Frontier Corps, a paramilitary force, was deployed in Bajur.
"Since it was ignored, not easily accessible, it was an ideal breeding ground," says Gen. Tariq Khan, the commander of the Frontier Corps.
In August, the Frontier Corps fought militants in one village in Bajur but was driven out with several dead and many more wounded. That's when the army was called in.
The army has since wrested control of the key road link from Khar, clearing the road of insurgents. As of late last week, troops were taking their offensive into the Mohmand tribal belt that borders Afghanistan.
The signs of battle litter the roadside: flattened markets, bomb craters and mud homes scarred by mortar fire.
At Nazirabad, six miles (10 kilometers) from Khar, troops faced a two-day battle against nearly 100 militants. Insurgents popped up from fields of shoulder-high corn stalks to launch rockets or fire bursts with Kalashnikov rifles, then seemingly disappeared, says Maj. Kamal, who gave only his first name. Two soldiers were killed and 22 wounded.
"We couldn't see where they were firing from," Kamal says. "We discovered later that they would fire at us and then run into caves hidden by the corn."
The army found an extensive network of caves and tunnels reminiscent of those dug in the 1980s by Western-backed anti-communist rebels in Afghanistan during the Soviet occupation. In one compound of nine mud homes surrounded by a high wall, the army found six underground rooms and a maze of tunnels.
Kamal climbs a precarious steel ladder that leads to a lookout. Peering over sandbags lined up against the mud wall, he points toward a dark speck in a series of eroded sandstone hills.
"That's another cave. The tunnel runs from here, 100 meters to there."
More caves lie at the end of a 20-foot-deep (6.1-meter-deep), narrow mud staircase barely wide enough for a thin person. Inside the small underground rooms, the army finds bedding and weapons, from anti-tank guns modified to fire 22 mm mortars to homemade bombs planted by roads and detonated from afar as military vehicles pass.
The Nazirabad compound was one of several hubs established by militants in Bajur, Kamal says.
"We were expecting a lot of resistance, but these tactics _ the tunnels. I never expected this," he says. "One room could hold five or six men."
Every day, Kamal's men search the caves to make sure the militants don't return.
The Bajur operation is an example of cooperation between the U.S. and Pakistan, with U.S. forces on the Afghan side of the border providing intelligence, surveillance and reconnaissance to Pakistani forces.
"The Pakistani army's drive to retake this Taliban hotbed demonstrates to the world that they are serious about tackling the threat of terrorism," says Brian Glyn Williams, associate professor of Islamic history at the University of Massachusetts.
However, Bajur is just one part _ the northernmost of seven major jurisdictions _ of the vast tribal belt that borders Afghanistan. The scorched-earth tactics in Bajur contrast with the softer approach taken farther south in another tribal area, Waziristan, where most of Pakistan's 70,000 soldiers are based. U.S. officials have questioned whether Pakistan is accommodating the insurgents in Waziristan rather than rooting them out.
U.S. Joint Chiefs of Staff Chairman Mike Mullen, visiting Pakistan last week, praised the Bajur offensive but also encouraged the military to step up efforts elsewhere.
Roughly nine miles farther, the convoy stops at Loi Sam, set in the middle of undulating corn fields.
This town has been flattened. The market that dominated the town square was pummeled to ruins. Electricity poles list to one side. The only gas station is half collapsed; giant holes mark where the pumps once stood.
It was early October when the army backed by fighter jets and helicopter gunships drove the militants out of Loi Sam. But less than a week later, the militants were back, firing at soldiers from the buildings that remained standing. Only after a fierce air assault did the army take full control.
From Loi Sam, it's a short drive past seared fields and ruined villages to Sabagai, barely two miles from Afghanistan.
A white banner hanging inside a militant's former home in Sabagai is signed by "relatives of the martyrs of Kashmir." The banner is worrisome evidence of coordination among militant groups in the tribal area and those battling India in the disputed territory of Kashmir.
Two secret meetings revealed earlier this year by the AP also suggested militants are pooling their resources. Several militant groups _ including Lashkar-e-Taiba, blamed by India in the Mumbai attacks, and Jaish-e-Mohammed, another group with links to Kashmir _ met to settle differences and forge common goals, according to a militant and a Pakistan military official.
The militants also called for a recruitment drive among the relatives of fighters killed in Kashmir. The banner in Sabagai suggests the drive has met with some success.
The persistence of the militants is sobering. Baloch gazes toward the towering peaks that embrace Bajur and straddle both Pakistan and Afghanistan.
"They are still out there," Baloch says. "They are everywhere around us. ... The best we can do is make it difficult for them to move and to have free run of the area."