Since 2001, al-Qaida largely has been driven out of its former base of operations in Afghanistan but not out of striking distance. The organization left a strong legacy in the country and continues to attack Afghan targets from outside the borders.

Al-Qaida is a militant Islamic terrorist network working to fight foreign influences in Muslim countries and carry out jihad, or holy war, to put Islamic fundamentalist governments in power. Suicide hijackers from the group flew airliners into the World Trade Center, the Pentagon and a field in Pennsylvania on Sept. 11, 2001, killing nearly 3,000 people.

In response, U.S.-led coalition forces invaded Afghanistan in October 2001, targeting al-Qaida members and overthrowing the Taliban government that sheltered them. The troops captured and killed some al-Qaida members and forced the remains of the organization to flee the country.

Al-Qaida suffered serious damage to its infrastructure and leadership, but survives in a decentralized form outside of Afghanistan. The group's two leaders, Osama bin Laden and Ayman al-Zawahiri, have managed to evade U.S. intelligence and, as of September 2006, were believed to be living in Pakistan.

"The network has been severely degraded, but it is still there and a lot of the personal connections are still there," Daniel Byman, director of the Center for Peace and Security Studies at Georgetown University, said in 2006. "If there isn't constant pressure there is a very good chance of a resurgence."

Since the U.S. occupation began, bombings by groups associated with al-Qaida have occurred in other regions, including Iraq and Western Europe. While al-Qaida has kept a lower profile around Afghanistan, a resurgence of attacks along the Pakistan-Afghanistan border by Taliban and other jihadist groups show some ties to the organization.

It is difficult to characterize the relationship between the Taliban insurgents and al-Qaida, but they are loosely affiliated, according to Greg Sullivan, a spokesperson for the State Department's Near East Asian Affairs bureau. Bin Laden plays a spiritual and philosophical leadership role to jihadists, but the operational logistics are being carried out by smaller groups in many cases.

Al-Qaida and the Taliban do have the shared goal in Afghanistan of driving out all foreign presence and reinstalling the Taliban as the government.

Afghanistan's democratically elected president, Hamid Karzai, who took power in 2002 with the endorsement of U.S. President Bush, took a strong stance against terrorism from the beginning of his presidency. He reacted with frustration to growing insurgent attacks in the country and called on the international community, especially Pakistan, to help root out terrorism at its source.

"We must concentrate on the sources of training and financing ... all that outside of Afghanistan, if we are to be able to defeat terrorism forever," Karzai said in September 2006.

Pakistani President Pervez Musharraf defended his country's policies on terrorism but acknowledged that al-Qaida and Taliban forces "are crossing from Pakistan's side and causing bomb blasts and terrorist activity" in Afghanistan.

Pakistan is probably the most central location of al-Qaida now, according to Byman, though the organization does not have a strong base of operations and training like it once enjoyed in Afghanistan.

Afghanistan's intertwined history with al-Qaida can be traced to the Afghan Mujahadeen, a group of international Muslim fighters that fought against the Soviet occupation of Afghanistan during the late 1970s and the 1980s.

Many of the Muslims that fought with the Mujahadeen were not from the country, but joined because of their dedication to jihad. The Mujahadeen received support and training from foreign governments, including the United States, Pakistan and Saudi Arabia.

Saudi-born bin Laden became one of the first Arabs to join the Mujahadeen in 1979. He helped organize and prepare fighters in Pakistan to cross into Afghanistan to battle the Soviets.

After the Soviets were successfully expelled, bin Laden founded al-Qaida in 1988 to consolidate the international network he had established.

The core goals of al-Qaida are the advancement of Islamic revolutions throughout the world, the establishment of fundamentalist Islamic regimes and fighting foreign intervention in Muslim countries.

Though bin Laden was in Saudi Arabia and Sudan for years after founding al-Qaida, in 1996 he returned to Afghanistan and made the country the network's home base. Afghanistan's de facto government, the Taliban, played a major role in this decision.

"Afghanistan would take them when no one else would," said Byman. "There was also a sense among some al-Qaida members that the Taliban was a true Islamic government, the only one."

The two groups formed a symbiotic relationship. The Taliban providing a base of operations, while al-Qaida provided defense for the group. The al-Qaida network recruited foreign fighters and trained them into elite fighting forces that backed the Taliban.

"Before the war, the people of Afghanistan were the main victims of al-Qaida," said Ashraf Haidari, political counselor at the Afghanistan Embassy in Washington, D.C.

"They supported the Taliban to victimize and oppress the people of Afghanistan."

As al-Qaida flourished in the country and expanded to train thousands of fighters, the network continued to organize terrorist strikes.

In 1998, bin Laden and al-Zawahiri released a fatwa, a declaration of war, against America.

"The ruling to kill the Americans and their allies -- civilians and military -- is an individual duty for every Muslim who can do it in any country in which it is possible to do it," the fatwa stated.

This message alerted the world to al-Qaida's violent intentions and turned attention on the country harboring the group. The August 1998 bombings of U.S. embassies in Kenya and Tanzania that killed 224 people were allegedly the work of al-Qaida members, creating even more criticism for Afghanistan.

The United States sought extradition of bin Laden and indicted him in connection with the bombings. The Taliban refused to turn him over, however, saying there was insufficient evidence to implicate bin Laden in terrorist activities.

The U.N. Security Council imposed air and economic sanctions on Afghanistan in October 1999 for refusing to cooperate. The sanctions were strengthened in December 2000 after pressure from the United States and Russia. Though the sanctions were damaging to the economy, the Taliban still refused to produce bin Laden.

After the 2001 terrorist attacks on U.S. targets, the Taliban would only go as far as asking bin Laden to leave the country, but would not force him out. The U.S. led invasion ensued, leading to more than five years of occupation of Afghanistan and the creation of a democratic government for the country.

Al-Qaida has suffered many losses, including the deaths of leading members Mohammed Atef in 2001 and Abu Musab al-Zarqawi, leader of al-Qaida in Iraq, in 2006.

But, while these victories for the U.S. war on terror were highly publicized in the United States and the smaller network itself has suffered, the jihadist movement continues to grow and as of October 2006 the United States still had not captured bin Laden.

-- By Talea Miller, Online NewsHour