The waning drone of B-52s over Afghanistan is signaling a new and in some ways trickier phase of the US war on international terrorism - at least on the diplomatic front.
As complex as the campaign in Afghanistan has been, it was still in essence a battle with a pariah regime whose only ally was an international terrorist group. But now, with the hunt for Al Qaeda leaders and the terrorist network that supports them moving beyond Afghan borders, the United States faces a new set of daunting challenges:
How does the US keep the pressure on Pakistan's President Pervez Musharraf to pursue Al Qaeda, without igniting a far more serious clash between Pakistan and nuclear rival India?
How much on-the-ground cooperation - or resistance - will the US encounter as it now enters nations such as Yemen, Sudan, and Somalia in search of Al Qaeda remnants?
Can the US make a move against Iraqi leader Saddam Hussein without shattering the international coalition Washington needs to fight the long-term war on terrorism?
Looking out over the coming days and weeks, some experts see promising signs for the US. Its military success in Afghanistan has translated into leverage against other countries with suspected terrorist activity, and that is already yielding some benefits.
Yemen, for example, took military action this week against suspected Al Qaeda militants. Local analysts said the strikes were designed to preempt US military action.
US officials lauded Yemen's action, which appeared to be the biggest anti-Al Qaeda operation by an Arab country since the Sept. 11 terrorist attacks. US Deputy Defense Secretary Paul Wolfowitz said Tuesday that US officials "have been urging the Yemenis to do more" about Al Qaeda training camps and suspected Al Qaeda operatives in the country.
The situation in Somalia could also turn in the US favor. Somali officials, who do not control all the African country's territory, say that international assistance would help eliminate any terrorist presence.
At a meeting of NATO defense ministers in Brussels, European officials briefed by US Defense Secretary Donald Rumsfeld said Somalia could be the next US target. Mr. Rumsfeld said that in addition to Yemen, Sudan also has active Al Qaeda cells, and Somalia has hosted its leaders.
As these events play out, however, the antiterrorism effort confronts several other hot spots that are much more worrisome - most notably the India-Pakistan conflict, which has popped up like a bad surprise.
"On one hand, the next phase of this war will focus on places like Yemen, Sudan, Somalia, Libya - places where by and large diplomatic pressure will be enough to get the action the US requires," says Lawrence Korb, a former Pentagon official and now vice president of the Council of Foreign Relations in New York. "But the real problem is going to be the situation between Pakistan and India."
What worries US officials is the threat of a blowup between the two nuclear rivals, who have moved closer to that after a shocking attack last week on India's parliament. Indian officials have declared the attacks the work of Pakistani Islamic extremist groups, working with the assistance of supportive Pakistani military intelligence officials.
The US, calling both countries "very close allies" in the war on terrorism, is trying to play the evenhanded friend to both. Commenting on the parliament attack, White House spokesman Ari Fleischer says, "This is not a reason for India and Pakistan to take action against each other. This is a time for [them] to take actions against terrorists."
Pakistan is of particular concern because of its historical support for Islamic militancy - it supported Afghanistan's Taliban regime before Sept. 11 - and because of President Musharraf's past support for separatist rebels in India-controlled Kashmir.
The US is watching for Musharraf to follow through on his pledge to take action against suspected terrorist organizations in the country that might have been involved in the India attack, State Department officials say. At the same time, with hundreds of Al Qaeda and Taliban fighters said to be disappearing across the Afghan border into friendly refuge in Pakistan, the US faces the touchier problem of pursuing the enemy within a friendly country.
Regional specialist Peter Tomsen says the "Islamist infrastructure" that has been built up in Pakistan over the same period is not going to be an easy target for the US to hit. Pakistan's military intelligence unit is the "cement that held the Afghan model [of the Taliban hosting and working with Al Qaeda] together," says Mr. Tomsen, who was the last US envoy to the Afghan resistance in the 1990s and is now an international relations specialist at the University of Nebraska at Omaha.
Musharraf removed some military officers as he bolstered relations with the US after Sept. 11, but those officials continue to direct from retirement much of the work of Pakistan's Islamic militants, Tomsen says.
Beyond these countries, some experts say they expect US diplomatic efforts against Iraq to ratchet up now - but no quick military action to topple Mr. Hussein.
The first step will be to further isolate Iraq and ensure that no terrorist groups, including any of those now fleeing Afghanistan, are able to intersect with Iraq's mass-destruction weaponry, says US Sen. Richard Lugar (R) of Indiana. If, subsequently, the US decides military action to remove Hussein is necessary, officials may have to consider whether the successful model of Afghanistan - air power working with local proxies - can apply.
And while the Afghanistan success paves an easier road for coalition-building against Hussein, Iraq still has more friends than the Taliban did before their demise.