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 US and Afghan charges that it is not doing enough to root out Taleban and Al-Qaeda fighters who crisscross the border. It is also the Pakistani military’s first foray into the Bajaur 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 US troops in Afghanistan have installed 68 motion sensors along the border to try to detect them.

In the meantime, the Pakistani Army has used helicopter gunships and fighter jets to blast entire villages in Bajaur 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 US questioning of the will of Pakistani soldiers to fight the militants.