First in an occasional series.

KABUL, Afghanistan - It seemed so easy five years ago: Anti-Taliban forces rolled into Afghanistan's capital after a monthlong American bombing campaign, and the repressive Islamist regime scattered like leaves in autumn.

With the Taliban gone, many Afghan men shaved their beards and some women cast off their burqas. But Osama bin Laden and the architects of 9/11 slipped away in eastern Afghanistan, and that should have been a clue to how elusive objectives could be in this fractious nation.

America turned its attention and resources to Iraq. But today the Taliban remnants have mutated into a different force - far deadlier, better organized and well-armed. With close bonds with the al-Qaeda international Islamist network, the insurgents have imported new skills previously unseen in three decades of war in Afghanistan - remote-control roadside bombs and suicide bombers.

Here, where the war on terror began after the 9/11 attacks, a cold, hard reality has set in - the battle has become a protracted counterinsurgency campaign that international officials say won't be resolved for years, even decades.

"This is not linear at all," said Army Lt. Gen. Karl Eikenberry, the commander of the U.S.-led coalition in Afghanistan. New forces have entered the mix - tribal chiefs, opium traffickers, and extremists experienced with the Iraqi conflict. "All this fuels on a militant ideology that has a way of resonating with the people here."

Afghans complain that U.S. policymakers paid too much attention to capturing a few high-value targets such as bin Laden, and not enough to addressing the more complex social and economic problems that made Afghanistan a welcome environment for Islamic extremists.

"I think that it was very naïve to believe after the fall of the Taliban in 2001 that that was the end of the Taliban," Afghan Foreign Minister Rangeen Dadfar Spanta said in an interview. "That was the reason why they concentrated only on the military action against the Taliban. But antiterror is a comprehensive project."

The top United Nations diplomat in Afghanistan agrees.

"Maybe it was a bit simple to think you could just extinguish this flame by sort of pushing them out or blowing them out," said Tom Koenigs, the head of the United Nations Assistance Mission in Afghanistan. "We were maybe too shortsighted."

Despite the trappings of democracy - elections, a new Parliament, a new constitution - President Hamid Karzai's government is hampered by rampant corruption, growing insecurity, and runaway opium production. The enthusiasm that accompanied him into office after elections two years ago has waned.

But Afghanistan is not without progress.

After the Taliban's fall, many feared that civil war would break out between rival ethnic and political factions, as happened before in Afghanistan and has since occurred in Iraq. But it hasn't this time. Karzai has held his weak government together, but at a cost - by striking a Faustian bargain to accommodate warlords, many of whom are now the sources of the discontent and insecurity that bedevil the government.

Afghanistan no doubt is a far different nation from what it was five years ago, when the repressively puritanical Taliban was toppled.

In the capital, foreign troops, aid workers and returning refugees have imported an international flavor. There are now diversions unknown during the Taliban's time - movies, private television and cell phones. Music blares from wedding halls, and private vehicles fill the streets. Simple pleasures forbidden by the Taliban - kite-flying, furtive flirting among couples on picnics in the park - are taken for granted.

But the foreigners also imported un-Islamic temptations - alcohol, prostitution, revealing clothing - that provide evidence for Taliban propagandists that Afghanistan has become a Western outpost of sin.

Cities such as Kabul, Jalalabad and Herat are experiencing construction booms, some of it no doubt funded by money from the burgeoning opium trade. Economists estimate that Afghanistan's drug economy is half as large as the legitimate economy, making impoverished Afghanistan more dependent upon an illicit enterprise than any other nation in the world.

In Kabul, where apartment blocks rise amid the ruins, the old and new collide sometimes in comical tableaux - at the marble-and-chrome Kabul City Center, traditionally dressed provincial Afghans shriek and stumble as they experience escalators for the first time.

Though women do not enjoy the liberties they had during the Soviet occupation in the 1980s, they have reentered the workplace. About 1.6 million girls are back in school. Women won 28 percent of the seats in Parliament's lower house, six more than the 25 percent the new constitution guarantees.

Millions of Afghans have returned from exile in Pakistan, Iran, Europe and the United States. They brought with them foreign expertise and broader worldviews. But they also brought competition for scarce resources. Real estate prices have skyrocketed in the larger cities, and the poor have been forced out farther to the outskirts. In rural areas, disputes have broken out between nomadic Kuchi herders and returning refugees reclaiming their lands.