KHOST, Afghanistan — This former Taliban stronghold, where Osama bin Laden spent time planning the Sept. 11 attacks, has become an American success story. The Taliban is being pushed out, and a government presence is extending into previously hostile territory.

Khost shows that, with the right combination of resources and leadership, it can be done. But Khost is not simply a good-news story. It also underscores a larger, troubling truth: The conflict in Afghanistan will be far more costly and much, much longer than Americans realize. This war, already in its seventh year, will eventually become the longest in American history, surpassing even Vietnam.

Success in Khost required some of America's best troops. Today elements of the legendary 101st Airborne Division — the Screaming Eagles of the Battle of the Bulge — are replacing troops from another storied unit, the 82nd Airborne, who, over 15 tough months, took Khost back. That success resulted from tactics developed locally by a stellar team: a courageous and honest provincial governor, Arsala Jamal, who has survived four assassination attempts; a creative American troop commander, Lt. Col. Scott Custer (yes, he is a direct descendant), who devised a more aggressive system of joint patrols with local Afghan army units; and a remarkable young Foreign Service officer, Kael Weston, who has established a direct dialogue with tribal leaders, university students, mullahs, madrassa students and even Taliban defectors.

As I saw in hours of meetings with these groups, Weston's intense hands-on process identifies problems and misunderstandings that might otherwise spiral out of control. One of these — serious enough to attract international media coverage and public expressions of concern from Afghan President Hamid Karzai — was the death of several women and children in two recent nighttime U.S. Special Forces actions. The tribal elders were blunt in our meeting; a white-bearded chief said, "Not even my brother can enter my house at night, but you Americans did not even knock." Gov. Jamal, his own closeness to the Americans making him even more vulnerable, was distraught. "This undermines everything we are trying to do here," he said.

Jamal and the elders understood that locally based American troops were not involved in the operations and that the targets were supposed to be an important Taliban cadre. Despite the furor, they stressed that they want the Americans to stay as long as necessary, knowing that will be a very long time; without NATO's continued presence, their government would fail. They have little confidence in the Afghan army, even though it seems to be improving, because there is as yet no indication that it can function in difficult conditions without active NATO support.

Moreover, the elders, like everyone else, despise the national police — Afghanistan's most corrupt institution. I heard firsthand accounts of blatant police shakedowns on the main roads, police destruction of agricultural produce because the officers were not paid off and direct police participation in the drug trade (which makes the police and the Taliban de facto partners).

The police are the front edge of Afghanistan's biggest problem. In conversations with more than 80 foreigners (diplomats, journalists, soldiers), Afghans in the private sector and, most important, senior members of the Karzai government, I found unanimity on only one point: The massive, officially sanctioned corruption and the drug trade are the most serious problems the country faces, and they offer the Taliban its only exploitable opportunity to gain support.

One case came up repeatedly, that of the notorious warlord Gen. Abdurrashid Dostum. After he attacked, brutalized (allegedly with a beer bottle) and almost killed a rival warlord recently, Dostum was not arrested, despite pleas from Afghanistan's chief law enforcement officials. The effect on Karzai's standing and reputation has been enormous. Excuses were made, but none justified his open disregard for justice.

This affair also highlights the conundrum Afghanistan presents the United States and NATO. There will be more successes like Khost as additional NATO troops, including 3,000 U.S. Marines, arrive later this year. But with each tactical achievement, Afghanistan will become more dependent on international support, which will always be better, faster and more honest than anything the government will be able to supply.

The effort in Afghanistan is vital to America's national security interests, and we must succeed — as the team in Khost has. But even as the United States and its NATO allies move deeper into the cauldron, questions must be asked: When, and how, will the international community hand responsibility for Afghanistan back to its government? Will short-term success create a long-term trap for the United States and its allies, as the war becomes the longest in American history?

Richard Holbrooke is a former U.S. ambassador to the United Nations. He wrote this commentary for The Washington Post.