Two years ago, my wife and I vacationed in Pakistan's Swat Valley. We spent an afternoon sightseeing in the hills, visiting stupas in the dense pine forests and carvings of the Buddha etched into sheer granite cliffs, remnants of the Buddhist civilization that had thrived in the valley for centuries. Later, we played badminton back at our hotel.

In those days, guest rooms were full, and policemen patrolled the streets. When I asked the hotel’s night manager about Maulana Fazlullah, the Taleban commander whose headquarters were just a few miles away, he put a finger to his lips and shook his head, reflecting the national response to the Swat Taleban: Ignore them, and they'll go away.

That policy, lambasted by many as appeasement, actually made sense in the context of Swat's relatively peaceable history and culture. But not long after our visit, Fazlullah’s cohorts began defacing the valley's rich legacy.

In October 2007, I went back to Swat to interview Fazlullah. This time, the hotel was vacant and the Taleban were conducting public lashings. In just months, Fazlullah had transformed Swat from an idyllic travel destination into a militant sanctuary. Still, the Pakistani government clung to the hope that he would just go away.

Then Fazlullah went a step too far. In April, a detachment of his fighters advanced out of Swat into the neighboring district of Buner, bringing them closer than ever to the capital, Islamabad. That finally got the attention of the Pakistan Army, which has been pounding the Taleban ever since. According to army spokesmen, the military has forced a Taleban retreat from Buner while reclaiming Swat’s main city of Mingora and re-establishing government control throughout the valley.

Now hopes are high in many quarters that the Pakistani military will ride this momentum into the more crucial battle — in South Waziristan, the home base of Baitullah Mehsud. Last week, the United States delivered four MI-17 cargo helicopters to Pakistan to support the army's fight against the Taleban. Pakistani President Asif Ali Zardari has called the Swat operation “just the start” and declared, with cheering from the Western sidelines, “We're going to go into Waziristan.”

But this enthusiasm should be tempered. The Obama administration has shown a refreshing realism in its policy toward Afghanistan and Pakistan, and if it wants to succeed there, it should encourage the Pakistan Army to stay out of Waziristan — at least for now.

South Waziristan is slightly smaller than Connecticut. Yet after a couple of thousand years of fighting — and defeating — anyone who has dared tread too close, Waziristanis have acquired an outsize reputation as recalcitrant tough guys. Unlike Swat, South Waziristan has been under Taleban rule for most of the past decade. In March 2004, Pakistani troops entered this southernmost tribal agency in their first bid to crush the militants. A month later, the Taleban were clobbering the army, and former President Pervez Musharraf was scrambling to find an exit strategy. Since then, the Taleban have repelled several other operations and, in 2007, kidnapped more than 200 soldiers.

Does that make it impossible for the Pakistan Army to defeat them today? Not necessarily. But it is unrealistic to believe that the Pakistan Army could continue fighting Taleban remnants in Swat, remain heavily deployed along the border with India and dedicate enough troops in South Waziristan to resemble a steamroller.

South Waziristan is far more complex, difficult and challenging terrain than Swat. A battle there would be no leisurely game of badminton.