PESHAWAR, PAKISTAN— After fighting peripheral wars against militants for the last several years, the military is poised to open a campaign in coming days against the Taliban's main stronghold in Pakistan's tribal areas, South Waziristan, according to senior military and security officials.

For three months, the military has been drawing up plans, holding in-depth deliberations and studying past operations in the area, where previous campaigns ended in failure and resulted in some of the military's highest casualties.

Even so, military officials said they expected stiff resistance once again in an area that one senior military official called the “;epicenter”; of the Taliban in Pakistan. It has also become a key base for al-Qaida. “;This is where we will be fighting the toughest of all battles,”; the official said.

He and other officials did not want to be identified while discussing confidential preparations for the campaign. But they said the military now seemed ready to try to re-enter the area, having decided it could wait no longer. “;If we don't take the battle to them, they will bring the battle to us,”; the official said.

The past two operations in South Waziristan ended up with the military bogged down and suing for peace, resulting in a series of accords that ultimately strengthened the hand of the militants.

An operation in January 2004 led to a peace agreement by that April, followed by another on Feb. 5, 2005, with Baitullah Mehsud, the leader of the Pakistani Taliban. But with few if any enforcement mechanisms, the accords were never sturdy and allowed the militants to regroup and tighten their hold on the region.

In late January 2008, the military launched another operation, called Zalzala, or Earthquake, with the declared goal of dislodging Mehsud. Only 12 days later, authorities were struggling to revive the peace accord.

With the failure of the operation went any pretense of state authority in Waziristan, with the government in effect ceding control to emboldened militants.

Military officials hope that things will be different this time, having taken on militant strongholds, each in their turn, in recent years in other areas: first in Bajaur, then in Mohmand, and, most recently, in the Swat Valley. Perhaps most critical was the elimination of Mehsud, whose death in a U.S. drone strike in August helped fracture the Pakistani Taliban, also known as Tehrik-i-Taliban. “;The Tehrik-i-Taliban Pakistan as a monolithic organization remains no more,”; a security official said.

Since June, Waziristan has been under an economic blockade, with thousands of army soldiers sitting on the fringes of the area, waiting for orders from the military high command to move in.

Some argue that the military should have mounted an operation immediately after Mehsud's death. “;As far as we are concerned, the operation should have been launched three months ago,”; said a senior government official. “;Baitullah is dead and his group seems to be in some form of disarray. And this provides the best opportunity to go after them.”;

But a senior military official said that, in addition to needing to wait for the forces and resources to be available, the military wanted to see what would be the repercussions of Mehsud's death.

“;We thought that Baitullah's death would unravel the Mehsud militant group and galvanize the tribe to stand up to the people they have suffered from,”; the official said. “;It didn't happen.”;

Now there is a sense within the military establishment that the situation in South Waziristan cannot be allowed to perpetuate. The blockade is nearly three months old, and the military, conducting limited airstrikes, is running out of targets.

The Pakistani army chief, Gen. Ashfaq Parvez Kayani, described Waziristan as an intelligence black hole. “;We have to move in,”; he said recently.

A large number of civilians have already relocated to Dera Ismail Khan and Tank, both in North-West Frontier Province, giving the army a relatively free hand to mount an operation.

But all agree that the battle ahead is formidable. Questions remain whether the army will be able to hold territory and sustain operations in a tough and treacherous terrain, where snows arrive in late November.

The Mehsud militants not only have the advantage of familiarity with the area, but their numbers—estimated at 6,000 to 7,000—have been thickened by foreign elements, in particular Uzbeks, who have a reputation as ferocious fighters.

Then there is the Haqqani network, which uses the area as a base for its operations in Afghanistan, and there is al-Qaida, which depends heavily on the Mehsud fighting force. “;They will defend their power base and fight till the very last,”; one officer said.