Better to underpromise and overdeliver - than overpromise and underdeliver. Someone should share this sage advice with the U.S. Army in Afghanistan, which has recently been promising Osama bin Laden's head on a silver platter by year's end.

We all hope the Army is right, of course, but the Green Machine should be careful about raising expectations and setting deadlines for the president, especially in an election year. This sort of stuff, which made headlines across the country, should come from Washington, not an Army public affairs office in Kabul.

Nothing wrong with being a little "forward-leaning," as Defense Secretary Rumsfeld is fond of saying, but managing expectations is important. In fact, Rumsfeld got it just right last week in Kabul, when he said, "The world will be a better place when he [Osama] is captured or killed. That is the goal of a great many nations . . . I suspect that we'll find that it's accomplished at some point in the future, and I wouldn't have any idea when."

Spring's approach will provide weather more conducive to operations against al Qaeda and Taliban fighters along the Pakistan-Afghan border. The Pakistanis and the Americans want to create a "hammer and anvil" effect, tightening the border and netting militants as they try to flee from one side to the other.

The Pakistanis have had some success already. President Musharraf's forces detained 25-plus suspected Taliban and al Qaeda militants in an operation last week in central Pakistan's Federally Administered Tribal Areas, nabbing Saudis, Egyptians, Yemenis, Uzbeks and Chechens.

Since casting off the Taliban after 9/11, Pakistan has been a key U.S. ally in the War on Terror, capturing more than 550 suspected al Qaeda and Taliban members.

This stepped-up effort by Islamabad is welcome and important - not only for the purpose of catching Osama bin Laden, his deputy, Zayman al-Zawahiri and Taliban leader Mullah Omar, but also in the broader effort to eliminate troublemakers eager to disrupt Afghanistan's national elections this June. To take down terrorism in that part of the world, the elections and the new Afghan government must be a success.

But even with more vigorous Pakistani cooperation and more American resources, such as Task Force 121 fresh from the Saddam hunt, catching top al Qaeda and Taliban bad guys remains a huge task. Here's why:

• There is precious little information on Osama's exact whereabouts. Although it's reasonable to think that he's hiding among sympathizers somewhere along the unruly Pakistan-Afghan border, he hasn't been heard from directly (except on videotape) since spring 2002. He's been using couriers to communicate with disciples ever since. We could nail this guy with a local's loose-lipped tip or a cell-phone slip, and it may happen yet.
  
  
• We're talking really rough territory. The Pakistan-Afghan border, from Baluchistan in the south to the North-West Frontier Province in the north, runs about 1,500 miles and is pretty inhospitable to searches. The northern and western borders include some of the world's highest peaks, including the famed K2 (28,250 ft). This terrain can make hiding a cinch and military operations a real challenge.
  
  
• Osama may be nowhere near the border. No al Qaeda bigwig has been captured in the countryside. They've all been arrested in large cities: Abu Zubaida in Faisalabad (central Pakistan), Ramzi bin Alshibh in Karachi (southern, coastal Pakistan) and Khalid Sheikh Mohammed in Rawalpindi (northern Pakistan).

Osama could even have made his way to Iran, which shares a border with Pakistan and Afghanistan. Several al Qaeda members now reside there, including his son, Saad bin Laden.

Bear in mind, too, that catching Osama won't end the War on Terror, just as catching Saddam Hussein didn't end resistance in Iraq. Al Qaeda is more than a terrorist group. It has grown to become an ideological movement. Al Qaeda has been weakened, but its ideology hasn't.

In fact, some would argue that its global jihad message has actually gained strength in the Muslim world. The al Qaeda theology will likely live beyond Osama's mortality.

As for those U.S. Army predictions from Kabul: Confidence among the warrior class is good, but overconfidence can be bad. Let's hope the Army is right - but it may be premature to write Osama's obituary just yet.

Peter Brookes is a senior fellow for National Security Affairs at the Heritage Foundation.