Al Qaeda missions have become more daring and deadly through the years. A turning point appears to be the unification of al Qaeda with one of the world's most lethal terrorist organizations and the signing of a fatwa ordering Muslim followers to kill Americans everywhere.

Ayman al-Zawahiri is the founder of Egypt's al-Jihad, a group that has been blamed for the assassination of former Egyptian President Anwar Sadat in 1981. The skilled surgeon served a three-year jail term on a weapons charge in connection with Sadat's killing.

Al-Zawahiri has been called bin Laden's heir apparent and he oversees many financial and communications functions within al Qaeda.

The two men met in Pakistan more than a decade ago, and it's believed that the older and more militant al-Zawahiri has influenced bin Laden's direction since that time. Like bin Laden, he comes from a prominent family and once inside Afghanistan he formed a faction of al-Jihad called the Vanguards of Conquest.

Al-Zawahiri's wife and his three daughters were killed during a bombing raid in eastern Afghanistan's Tora Bora region last December. The 51-year-old was quoted by a London-based Arabic newspaper as saying that his family members died as martyrs.

Recent reports indicate that bin Laden, a diabetic with a history of kidney problems, left Tora Bora on horseback during the height of the bombing. It's possible that Al-Zawahiri, who serves as his personal physician, was part of the small party that travelled with him to Pakistan.

Weeks earlier, Interpol issued an arrest warrant for al-Zawahiri without specifically linking him to the Sept. 11 attacks. The warrant, made at the request of Egyptian police, says he is "considered to have masterminded several terrorist operations in Egypt" and is "accused of criminal complicity and management for the purpose of committing premeditated murders."

The U.S. State Department in 1997 named al-Zawahiri as the mastermind behind the killing of 57 foreign tourists in Egypt. He was sentenced to death in absentia two years later by an Egyptian court. Since leaving Egypt in the 1980s, he has lived in Saudi Arabia, Pakistan, and Afghanistan.

Federal prosecutors allege in court documents that a Toronto man being detained as a security threat has terrorist ties to a group headed by the al Qaeda lieutenant. Mohamed Zeki Mahjoub's lawyer is fighting a deportation order on the grounds his client will likely be executed if he is returned to Egypt, where he was convicted in absentia of terrorist activities.

In court documents, Mahjoub describes working for bin Laden in Sudan where he managed a large farm, but he denies knowing about the Saudi-born dissident's role in al Qaeda. Egyptian authorities believe Mahjoub is a member of the Vanguards of Conquest.

Another man is being held in Canada due to alleged terrorist ties to al-Zawahiri and bin Laden. Mahmoud Jaballah, a co-founder of a private Muslim school in Toronto, is awaiting a hearing to decide whether he can remain in Canada. In 1999, a federal court judge quashed a national security certificate issued against Jaballah that accused him of being linked to al-Jihad.

A possible silent partner

One of the world's most dangerous terrorists is also the most mysterious. Lebanese Hezbollah leader, Imad Mughniyeh, pioneered suicide bombings in the Middle East and directed a seven-year string of violent hostage takings targeting Americans in Beirut during the 80s.

Sarah Meyers writes that Israeli military intelligence claims to have evidence that al-Zawahiri and Mughniyeh directed the September 11 suicide hijackings. The assertion contained in a World Markets Research Centre report would explain why bin Laden included liberal references to Palestine in his public statements following the attacks.

"Mughniyah is not just a mastermind, he's the master terrorist," a U.S. counter-terrorism official told The Times of India. "He introduced many tactics that others use to this day. The U.S. has been trying to nab him since the early 1980s, but he's evaded capture every time we got close. We're not even sure what he looks like any more."

The hands-on Mughniyeh was one of the first to appear on the FBI's most wanted terrorist list following the 1985 hijacking of a TWA flight from Athens to Rome.

Perhaps his expertise contributed to the surreal success of the suicide hijackers that attacked the World Trade Center and the Pentagon. Armed only with box cutters, the terrorists managed to hijack all four of their known targets. Three of the jets were transcontinental flights bound to Los Angeles and San Francisco but managed to swing east without being intercepted.

Two wide-body 767s, which had the largest fuel capacity of the hijacked planes, were chosen for the World Trade Center attacks and account for only three per cent of the United Airlines fleet. The flights were commandeered by five-member teams, with the exception of the plane that crashed in a Pennsylvania field, which had four hijackers aboard.

The well-executed script pushed beyond the edge of the envelope and bears the patina of an accomplished warrior. It is known that al Qaeda established a working relationship with Hezbollah in the early 90s. But while bin Laden has gravitated toward the public spotlight, the enigmatic Mughniyeh moves in the shadows.

Only a few early dated photos of Mughniyeh exist in the public domain. The Shi'ite Muslim primarily works out of Lebanon against neighbouring Israel. Mughniyeh has received support from at least one state and he moves freely between his home base in Lebanon and Iran. The Lebanese radical is believed to be in his 40s.

Marriage of convenience

Mohammed Atef served as bin Laden's military advisor and joined the movement during its earliest days. A senior Taliban official said the Egyptian-born militant was killed during an air strike near Kabul along with seven other members of the al Qaeda network last November.

American prosecutors say Atef provided training and assistance to the Somali tribes responsible for killing American Army Rangers after their Black Hawk helicopters were shot down in Mogadishu. U.S. Attorney Mary Jo White also blamed Atef and bin Laden for the 1998 twin bombings of American embassies in East Africa.

Atef moved to Afghanistan to fight the Soviets during the 80s. His relationship with bin Laden can also be traced to the Sudan where the Saudi-born dissident lived before returning to Afghanistan in 1996.

Bin Laden, al-Zawahiri, and Atef often made public appearances together. They held a news conference prior to the 1998 U.S. embassy bombings in Africa and all three were later indicted for the attacks. In the past, the release of any video statement from al Qaeda signified that a major terrorist attack was pending.

Bin Laden, who has four wives and more than 20 children, has used marriage as a strategic tool throughout his life. His eldest son, Mohamed, wed Atef's daughter at a January 2001 wedding in the southern Afghanistan city of Kandahar. The ties that bind extend even further.

One of bin Laden's daughters is married to Taliban leader Mullah Mohammed Omar, which solidified his base within war-torn Afghanistan during the 90s. A brother-in-law serves as one of his chief financial officers, while another is a key leader in Abu Sayyaf, a Muslim guerrilla group based in the Philippines.

The new arrivals

A new chief of operations moved in to fill the void left by the death of Mohammed Atef as 2001 drew to a close. But Abu Zubaydah's tenure was limited to a few brief months. He was captured in Pakistan in late March and transferred to the United States.

The 30-year-old Saudi-born Palestinian is believed to know the identities of thousands of trainees who have passed through training camps in Afghanistan. American intelligence also believe that he was at bin Laden's side in the weeks immediately following the Sept. 11 attacks.

During court testimony, convicted terrorist Ahmed Ressam said that Zubaydah approved and covered his expenses for training in Afghanistan. In return, the former Montreal resident said he was asked to supply passports for operatives to carry out missions in the United States.

Zubaydah, who was shot in the groin, thigh, and stomach during his capture, is being questioned at an undisclosed location. U.S. officials say information provided by Zubaydah led to the arrest of Jose Padilla for the role he played in an alleged "dirty bomb" plot earlier this year.

Still, one source told CNN that some of the information Zubaydah is passing along could be false. "Guys like that are quite capable of lying for effect," he said. Zubaydah is the only high-ranking al Qaeda official to be captured since the war on terror began.

A series of videos released last fall by al Qaeda through al-Jazeera television revealed that an entirely new presence was emerging inside bin Laden's inner circle. Sulaiman abu Ghaith, a 37-year-old father of six, appeared in several videos released by the group and broadcast worldwide.

Ghaith fled Kuwait for Afghanistan in June 2001. He gained attention in Kuwait during the Iraqi occupation for his sermons against Baghdad and Iraqi President Saddam Hussein. He was later banned when he turned against the Kuwaiti government and was stripped of his citizenship following his al Qaeda address.

How al Qaeda works

The Contractor
Al Qaeda has a hierarchical structure that is often seen in the corporate world. Osama bin Laden, who is known as "The Contractor," acts as the head CEO. In addition to his own personal wealth that he has increased by developing a series of businesses, he is known as a shrewd fundraiser. Al Qaeda is Arabic for base, a name chosen by bin Laden when he formed the group following the Soviet war in Afghanistan.

Key Lieutenants
The key leaders in al Qaeda are bin Laden's trusted advisors. Ayman al-Zawahiri is the founder of Egypt's al-Jihad, a terrorist group blamed for the assassination of Anwar Sadat. He is bin Laden's top advisor and is often seen standing beside him in videos released by the group. Bin Laden is linked through marriage to Muhammad Atef who served as his military chief for more than a decade. His eldest son married Atef's daughter in January 2001.

Cell Divisions
Training manuals developed by al Qaeda and seized by authorities indicate the organization operates on the basis of secrecy and security. The cells are usually small and members of one cell may not know members of another. So-called sleeper cells may remain inactive for years before being called to duty. It's believed that terrorist activities are divided into three phases: research, planning, and execution.

Global Reach
Al Qaeda cells are believed to operate in more than 60 countries. Membership is estimated to be anywhere from several hundred to several thousand. The core group was drawn from a pool of the thousands of freedom fighters that fought in Afghanistan against the Soviet occupation. A second generation of members has been primarily involved in terrorist activities and they are often educated and well-travelled recruits still in their 20s.