Born in Jeddah, Saudi Arabia, his family originally came from Yemen.

Sheik Abdullah Azzam, a Palestinian religious scholar, establishes the Makhtab al Khadimat -- the Office of Services -- in Peshawar, Pakistan to recruit an Islamic army to fight the Soviets in Afghanistan. Osama bin Laden provides financial support to Azzam's organization.

Bin Laden establishes Al Masadah ("The Lion's Den"), a training camp for Persian Gulf Arabs. Bin Laden begins associating with Egyptian radicals -- who, unlike Sheik Abdullah Azzam, advocate a global jihad beyond Afghanistan -- and befriends Dr. Ayman al-Zawahiri of the Egyptian Islamic Jihad.

The journal published by the Office of Services is distributed in the U.S. by the Islamic Center of Tucson, Arizona.

Osama bin Laden -- along with Muhammad Atef and Abu Ubaidah al Banshiri -- founds Al Qaeda ("The Base"). The organization operates out of Afghanistan and Peshawar, Pakistan.

Read more about Al Qaeda's establishment in the U.S. indictment of Osama bin Laden.

After a car bomb kills Sheik Abdullah Azzam, a battle for control of the Office of Services breaks out between those who believe the jihad should focus on the creation of an Islamic state in Afghanistan, and extremists sympathetic to Osama bin Laden, who want to expand the struggle worldwide. The extremist faction eventually takes control.

At a conference of Muslims held in Oklahoma City, Wadih el-Hage, a U.S. citizen later convicted in the 1998 U.S. embassy bombings trial, meets with Egyptian Mahmud Abuhalima, who is later convicted for his role in the 1993 World Trade Center Bombing. Abuhalima later tries to buy guns from el-Hage.

For more details on el-Hage's Al Qaeda connections, read FRONTLINE's "A Portrait of Wadih el-Hage".

The Soviets' humiliating defeat by mujahedeen forces in their 10-year long war inspires Osama bin Laden and other Islamic radicals to believe their victory in Afghanistan can be replicated around the world. At the end of the war, many of the "Afghan Arabs," as the radicals were called, returned home. Osama bin Laden returns to Saudi Arabia.

During an investigation into the assassination of the right-wing rabbi Meir Kahane, authorities discover bomb manuals and photographs of the World Trade Center and the Empire State Building in the apartment of an Egyptian, El-Sayyid Nosair. Nosair reportedly is an associate of Wadih el-Hage.

It is later learned that Nosair's legal bills in the WTC bombing trial were paid for by bin Laden. This is the earliest known intelligence information linking bin Laden to terrorists.

Bin Laden leaves Saudi Arabia and travels to Afghanistan with some of his supporters. By 1992, they finally settle in Khartoum, Sudan.

Read more on FRONTLINE's "Hunting bin Laden" chronology.

According to a document released by the British government after the Sept. 11 attacks, between 1992 and 1993, Mohammed Atef, an Egyptian aide to bin Laden, travels frequently to Somalia to organize violent attacks on U.S. and U.N. troops stationed there. After each trip he reports back to bin Laden in Khartoum.

According to the U.S. indictment of bin Laden, between 1992 and 1996 Al Qaeda makes overtures to Iran and Hezbollah to take part in a global war against the U.S. The indictment alleges that Mamdouh Mahmud Salim, an Al Qaeda leader, met with Iranian officials and that Al Qaeda sent members to Lebanon to receive training from members of Hezbollah. American officials also claim that around this time bin Laden's group begins an effort to secure components for chemical and nuclear weapons.

In an apparent plot to kill U.S. servicemen headed to Somalia, a bomb explodes at a hotel in Aden, Yemen and kills two Austrian tourists. Two Yemeni Muslims -- who had been trained in Afghanistan -- are injured and later arrested. Intelligence officials believe this is Al Qaeda's first attack.

The Associated Press later reports that two of the Yemenis detained for the 2000 attack on the USS Cole were involved both in this 1992 Aden bombing, and a series of other attacks in 1993.

A truck bomb explodes in the parking garage of the World Trade Center (WTC) killing six and injuring hundreds. Investigators discover the suspects have links to a network of Islamic extremists. Several people eventually convicted in the bombing are linked to the Office of Service's Al Kifah Center in Brooklyn; four of these men are connected to Sheik Omar Abdel Rahman. Rahman, a blind Egyptian cleric who was the spiritual leader of the Egyptian Islamic Jihad, is later convicted of conspiracy for his involvement in a plot to blow up New York City landmarks. He is sentenced to life in prison.

Investigators charge Ramzi Yousef as the mastermind behind the WTC bombing and begin a worldwide manhunt. They discover immigration officials had already detained Ahmed Ajaj, a Yousef associate, when he entered the U.S. carrying terrorist training manuals.

Osama bin Laden's name surfaces during the 1993 WTC investigation as a financier of the Office of Services. His name is also found on a list of individuals who was called from a safe house used by the conspirators. During the WTC bombing trial, bin Laden's name appears on a list of potential unindicted co-conspirators, but Al Qaeda is never mentioned.

According to a document published by the British government, Muhammad Atef, Saif al Adel and other members of Al Qaeda return to Somalia to train Somali forces to attack U.N. troops.

Pakistani Abdul Hakim Murad -- later convicted for his role in the 1995 Bojinka ("Big Bang") plot to blow up twelve airliners -- meets Khalid Shaikh Mohammed at Mohammed's house in Karachi, Pakistan while visiting with Ramzi Yousef. Murad would later tell investigators that Khalid Shaikh Mohammed -- suspected of helping to plan the Sept. 11 attacks -- had an “intense” interest in pilot training.

Eighteen American soldiers are attacked and killed in Mogadishu, Somalia. A U.S. indictment later charges bin Laden and his followers with training the attackers.

Read more about the incident on FRONTLINE's "Ambush in Mogadishu" Web site.

Members of an Al Qaeda cell in Kenya discuss attacking the U.S. embassy there. Ali Mohamed, a U.S. citizen, later admits to investigators that he took photographs and sketches of the embassy and presented them to bin Laden in the Sudan.

A group of Algerian hijackers seize an Air France flight headed for Paris. The crisis ends after French commandos storm the plane. According to some French investigators, the hijackers planned to blow up the plane above Paris or crash it into the Eiffel Tower.

Ramzi Yousef, suspected mastermind of the 1993 WTC attack, hides out in the Philippines with Khalid Shaikh Mohammed, believed to be his uncle. The two reportedly plan a number of potential terrorist attacks.

By January 1994, bin Laden is reportedly supporting at least three Sudan training camps.

According to a later U.S. indictment, bin Laden sets up a media information office in London which will serve as a message center and provide cover for Al Qaeda operations. The center is run by Khalid al-Fawwaz.

In Marrakesh, Morocco, two Spaniards are killed when three French Muslims open fire on tourists in a hotel lobby. European investigators reportedly discover phone calls between the suspects and the Office of Services. They also start to uncover a network of Afghan jihad war veterans in Europe.

Investigators come to suspect that a company named Konsojaya is a front for funneling money from bin Laden to regional operatives. Wali Khan Amin Shah, a Pakistani, and an Indonesian cleric named Riduan Isamuddin (AKA "Hambali") established the company. A number of phone calls are made from Konsojoya offices to Mohammed Khalifa, bin Laden's brother-in-law, who allegedly ran a charity front for Al Qaeda. The Hambali connection to this group is only discovered after Sept. 11.

2004 Update: "Hambali" now in U.S. custody - see details.

Ramzi Yousef plants a small bomb on a Philippine Airlines plane. The bomb explodes during the second leg of the trip and kills a Japanese businessman. Authorities later discover the bombing is a test run for the planned Bojinka attack.

Following an explosion in a Manila apartment, Philippine police uncover a plot -- code-named Bojinka or “Big Bang” -- to blow up 12 airplanes bound for the U.S. Authorities arrest Abdul Hakim Murad, a Pakistani who is an associate of Ramzi Yousef. Yousef flees to Pakistan.

Investigators also discover that Khalid Shaikh Mohammed had visited the apartment frequently. His name is found on documents inside a computer that contain details of the Bojinka plot.

In the Bojinka investigation, Manila police interview Abdul Hakim Murad. According to their report, Murad describes his discussions with Ramzi Yousef about hijacking a commercial aircraft and flying it into the headquarters of the CIA.

Yousef and Murad also reportedly discuss the idea of using a small airplane loaded with explosives to bomb targets in the U.S.

Just as FBI Agent John O'Neill begins his new job as section chief of the FBI's Counterterrorism Section, Yousef is located in Pakistan. O'Neill helps coordinate his capture. Afterwards, authorities learn Yousef spent part of the previous three years living in a bin Laden-funded guesthouse.

Bin Laden sends an open letter to King Fahd of Saudi Arabia calling for a campaign against U.S. forces in Saudi Arabia.

Wali Khan Amin Shah is arrested in Malaysia and rendered to the United States. He is later convicted for his role in the Bojinka plot.

The U.S. State Department issues a dossier on bin Laden that claims he is a financier of radical Islamic causes and connects him to the 1992 hotel bombing in Aden, Yemen and the training of the Somalis who attacked U.S. troops in Mogadishu. At the same time, a grand jury investigation of Osama bin Laden is initiated in New York.

The FBI and CIA create a joint station, code-named “Alex,” with the mission of tracking down bin Laden. Richard Clarke would later tell FRONTLINE that with the establishment of Station Alex, “We were able over the course of about 18 months to go from thinking there was a bin Laden network to seeing it in 56 countries.”

Under international pressure, Sudan expels bin Laden. He and his followers return to Afghanistan.

Jamal Ahmed al-Fadl leaves Al Qaeda after he's discovered embezzling money from the organization. Al-Fadl begins cooperating with the U.S., providing information on Al Qaeda's organization and how it operates.

Nineteen American soldiers are killed and 500 people injured in the bombing. Investigators will eventually conclude that the most likely scenario is that the Iranian government commissioned Saudi Hezbollah terrorists to carry out the attack. [See Richard Clarke interview.] Others, however, are convinced bin Laden played some role in the attack.

Ramzi Ahmed Yousef, Abdul Hakim Murad, and Wali Khan Amin Shah are convicted for their role in the Bojinka plot.

The Associated Press reports that senior FBI officials have determined terrorist groups are operating in America. The AP quotes John O'Neill, who is now special agent in charge of the national security division in New York as saying, “Almost every one of these groups has a presence in the United States today. A lot of these groups now have the capacity and the support infrastructure in the United States to attack us here if they choose to.”

Police search Wadih el-Hage's home in Nairobi, Kenya. On his computer they discover documents, which outline the presence of an Al Qaeda cell in Nairobi. Read more on FRONTLINE's "Hunting bin Laden: Warnings to the FBI"]

After the raid, el-Hage is questioned but not detained, and he returns to America. In the fall, el-Hage denies his involvement in terrorism to a New York grand jury.

Bin Laden and Dr. Ayman al-Zawahiri issue a declaration with other extremist groups calling on Muslims to kill Americans anywhere in the world.

Read their statement on FRONTLINE's "Hunting bin Laden" chronology.

A U.S. grand jury issues a sealed indictment charging bin Laden with conspiracy to attack “defense utilities of the United States.” The indictment alleges bin Laden is involved in the October 1993 attack on U.S. soldiers in Somalia.

John Miller of ABC News interviews bin Laden in his mountaintop camp in Afghanistan. During the interview bin Laden admits to knowing Wali Khan Amin Shah, one of the Bojinka plotters, but denies having met Ramzi Yousef. He also denies knowledge of the “Bojinka plot” or a related plot to assassinate Clinton.

Watch the interview on FRONTLINE's “Hunting bin Laden” Web site.

The Federal Aviation Administration warns airlines to be on a “high degree of alertness” for possible hijackings by Al Qaeda.

The group, led by Dr. Ayman al-Zawahiri, warns of a “message” they will be sending to Americans, “which we hope they read with care, because we will write it, with God's help, in a language they will understand.”

American embassies in Nairobi, Kenya and Dar es Salaam, Tanzania are bombed almost simultaneously. The Kenya bombing kills 213 and injures 4,500; the Dar es Salaam bombing kills 11 and injures 85. One of the bombers, Mohamed Al-'Owhali, a Saudi, flees the scene.

During the investigation, a search of the apartment of Khalid al-Fawwaz, the head of Al Qaeda's London office, reveals manuals virtually identical to those found in the luggage of Ahmad Ajaj, who was connected to Ramzi Yousef and the 1993 World Trade Center bombing.

Mohamed Sadeek Odeh, a Jordanian who would later be convicted in the embassy bombings trial, is arrested in Pakistan when he tries to enter from Kenya with a fake passport.

A group calling itself the Islamic Army for the Liberation of the Holy Places faxes claims of responsibility for the attack to different media organizations in France, Qatar, and the UAE. According to a document published by the British government, a later investigation reveals that the fax was sent from a telephone number linked to Osama bin Laden.

Mohamed al-'Owhali is arrested by Kenyan detectives and confesses to his role in the embassy bombing. Intelligence officials intercept calls between two bin Laden lieutenants implicating them in the embassy bombing. Advisors also warn President Clinton that they have evidence that bin Laden is attempting to purchase weapons of mass destruction.

President Clinton orders Tomahawk missiles fired at a suspected Al Qaeda camp in Afghanistan and a pharmaceutical plant in Sudan, which was suspected of producing chemical weapons for bin Laden. The effectiveness of the strikes is later questioned.