Feb. 23, 1998 Al Qaeda and other jihadist groups formally joined, including Ayman al-Zawahiri's Egyptian Islamic Jihad.

Aug. 20, 1998 Missiles launched at bin Laden's camps in Afghanistan and a suspected chemical weapons factory in Sudan.

Sept. 13, 2001 Secretary of State Colin Powell identifies terrorist mastermind Osama bin Laden as the prime suspect in Sept. 11 attacks on the World Trade Center and the Pentagon.

Sept. 14, 2001 Afghanistan's Taliban militia warns of "revenge" if the United States attacks the Asian country for harboring bin Laden.

Sept. 16, 2001 President Bush pledges "crusade" to "rid the world of evil-doers" and brushes off a reported bin Laden denial of involvement in the terrorist attacks on the United States. Vice President Dick Cheney warns that those who harbor terrorists face "the full wrath of the United States."

Sept. 18, 2001 Hundreds of Islamic clerics gather in Kabul, Afghanistan, to discuss conditions for extraditing bin Laden to a country other than the United States. Taliban leaders call on Muslims to wage holy war on America if it attacks.

Sept. 23, 2001 Powell announces a $25 million reward for information leading to the apprehension of bin Laden. The next day, the suspected terror mastermind calls on Pakistan's Muslims to fight "the American crusade."

Sept. 30, 2001 The Taliban say explicitly for the first time that bin Laden is still in Afghanistan and is being kept in a location secret from the outside world. The Pakistani president says, even under the threat of U.S. military strikes, hopes are "very dim" bin Laden would be surrendered.

Oct. 2, 2001 The NATO secretary-general says the United States has provided its 18 NATO allies with "clear and compelling" evidence of bin Laden's involvement in the Sept. 11 attacks.

Oct. 5, 2001 New images of bin Laden appear on an Arab television station, showing the terror suspect somber and composed amid a celebration by his followers at an arid mountain base.

Oct. 7, 2001 The U.S. and Britain begin air strikes against Taliban military installations and bin Laden's training camps inside Afghanistan. In a videotaped statement aired after the strikes, bin Laden praises God for the Sept. 11 terrorist attacks in the United States.

Oct. 10, 2001 The White House releases a list of 22 "Most Wanted Terrorists," including bin Laden and others indicted in connection with five major terrorist incidents in the '80s and '90s.

Oct. 11, 2001 President Bush holds a prime-time news conference at the White House, saying it may take "a year or two" to track down bin Laden and his terrorist network in Afghanistan, but asserts that after a five-day aerial bombardment, "we've got them on the run."

Oct. 21 Asked if U.S. forces would kill bin Laden on sight, Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, says it depends on what happens when he's found. "If it's a defensive situation, then bullets will fly, but if we can capture somebody, then we'll do that," he says.

Oct. 25, 2001 Defense Secretary Donald H. Rumsfeld said the U.S. military campaign in Afghanistan was hurting the Taliban as well as the al-Qaida terrorist network, but that finding bin Laden was proving difficult. "It's like finding a needle in a haystack," he says.

Oct. 30, 2001 The Defense Department acknowledges there are "modest number" of covert U.S. troops inside Afghanistan hunting down bin Laden and al-Qaida leaders, along with helping opposition forces oust the Taliban.

Nov. 11, 2001 In the second part of an interview published in a Pakistani newspaper, bin Laden declares he would never allow himself to be captured.

Nov. 19, 2001 A Pentagon spokesperson says more U.S. commandos have been deployed in southern Afghanistan to help the hunt for bin Laden. The Pentagon hopes the Taliban collapse and millions in U.S. reward money will motivate Afghans to help find bin Laden.

Nov. 21, 2001 The Pentagon says the U.S. Navy would board cargo ships suspected of carrying bin Laden or other al-Qaida leaders who might flee Afghanistan by sea.

Dec. 3, 2001 Rumsfeld says U.S. forces will do "whatever is necessary" to root out bin Laden from cave hide-outs around Kandahar and in mountains in eastern Afghanistan.

Dec. 8, 2001 Afghanistan's interim leader Hamid Karzai calls on fellow Afghans to capture bin Laden and Taliban leader Mullah Mohammed Omar and promises to bring the two men to "international justice."

Dec. 10, 2001 U.S. bombs rain down on al-Qaida's Tora Bora cave complex as the hunt for bin Laden intensifies in the east, where it is suspected that bin Laden is hiding.

Dec. 17 Tribal fighters and U.S. special forces chase al-Qaida guerrillas through the mountains of eastern Afghanistan after conquering their complex of caves and tunnels. Some tearful al-Qaida fighters surrender, but there is still no word on the whereabouts of Osama bin Laden.

Dec. 25, 2001 Sources say the United States has asked Yemen to allow U.S. Marines to take part in what has been a deadly hunt for al-Qaida members. A Western diplomat says the United States also has proposed setting up a joint task force in Yemen that would include officials from the CIA and other agencies to coordinate operations.

Dec. 26 Qatar-based television station Al-Jazeera airs a video of Osama bin Laden, apparently made in recent weeks. In the video, he calls for attacks against the U.S. economy.

Dec. 28, 2001 With Pakistani officials saying they may need to pull away troops patrolling the Pakistan-Afghanistan border to deal with a possible conflict with India, President Bush says the U.S. military will not end the search for bin Laden until he is killed or brought to American justice.

Jan. 8, 2002 The U.S. military announces they have determined that Osama bin Laden is not in the Tora Bora cave complex.

March 6, 2003 After running cold for more than a year, bin Laden's trail heats up following the March 1 arrest of Khalid Shaikh Mohammed. Mohammed, a man thought to be the No. 3 figure in al Qaeda, tells interrogators he met with the terror mastermind just weeks earlier. Pakistani and American forces begin an intense search for bin Laden along a southwestern stretch of the border with Afghanistan.

April 15, 2004 Bin Laden offers "truce" to European countries that do not attack Muslims; vows revenge against the U.S.

March 2005 In the first definitive statement from the Pentagon that bin Laden was at Tora Bora and evaded U.S. and Afghan forces, a document shows one of the terror leader's former commanders who aided his escape is being held by U.S. authorities.

Jan. 19, 2006 Osama bin Laden makes new threats against the U.S. in his latest audio tape, but also suggested a truce. The White House says flatly, "We don't negotiate with terrorists." Officials say the threats are not being dismissed, but the threat level is unchanged.

May 23, 2006 In an audio tape posted on the Internet, a speaker claiming to be bin Laden said that neither Zacarias Moussaoui -- the only person convicted in the U.S. for the Sept. 11 attacks -- nor anyone held at Guantanamo had anything to do with the al-Qaida operation. "I am the one in charge of the 19 brothers and I never assigned brother Zacarias to be with them in that mission," he said, referring to the 19 men who hijacked the four aircraft used in the Sept. 11, 2001, attacks.