Editor's note: Abdel Bari Atwan is editor of al-Quds al-Arabi, a London-based pan-Arab daily newspaper. He is author of The Secret History of al Qaeda and is currently working on his next book, Al Qaeda: The Next Generation. In May 2010 Middle East magazine named Atwan as one of the 50 most influential Arabs.

(CNN) -- I spent three days with Osama bin Laden in 1996 when I traveled to the remote, mountainous Tora Bora area of Afghanistan to interview him. I found him gently spoken, humble -- even shy -- and extremely polite. It is difficult to reconcile these personal memories of the man with the fact that he presided over so much terror and destruction.

Why did he hate the Americans so much? Why did he turn to the most extreme form of radical Islam and why did he chose violence to express this hatred and this faith?

His extraordinary metamorphosis may have started in childhood. Osama was the 43rd of 53 siblings but somehow in the chaotic scramble for attention he became his millionaire father Muhammad Awad bin Laden's favorite. His brothers have described him as aloof and quiet as a child -- while others of his age were playing outside or engaged in the noisy chatter and petty squabbles that characterize most childhoods, Osama preferred to accompany his father to business and religious meetings, sitting silently by his side.

At the age of 10, Osama's life was turned upside down when Muhammad Awad's private plane crashed and all on board were killed. The pilot who made the fatal error of judgement was American. It is possible that Osama's later antipathy towards the U.S. was compounded by this tragedy.

After Muhammad's death, the family continued his tradition of offering hospitality to pilgrims during the Hajj season. As he entered his teens, Osama was already in the habit of discussing theology with these visitors, some of whom espoused the Salafist form of Islam and introduced the young man to the radical teachings of Sayyid Qutb, which clearly resonated with Osama.

Unlike many wealthy Saudis, Osama wasn't beguiled by the west. He decided to marry his cousin, Najua Ghanem, when he was only 17, and involved himself in the family construction business. He saw himself as occupying the moral high ground even then and his criticisms of western values -- or lack of them -- later became a recurrent theme in his speeches and informed his impulse towards jihad with an atheistic, "infidel" west.

When the U.S.S.R invaded Afghanistan in 1979, resistance erupted in the form of the Islamic mujahedeen. By now, Osama had become the protégé of the radical Islamist scholar Abdullah Azzam, who preached that incitement and jihad were religious duties. In 1982, when he was 25, Osama decided to relinquish his privileged and comfortable life and head for the front line.

In Afghanistan, Osama came face to face with the U.S. military advisers who were arming and training the mujahedeen. When the Soviet troops finally withdrew in 1989 the U.S. began to worry about possible "blow-back" from the hard core of battle-hardened militant Islamists that remained.

Osama learned (from Pakistani intelligence, interestingly) that he was among a group of men targeted for assassination by the CIA. He fled back home only to find himself placed under house arrest. Not surprisingly, perhaps, Osama felt the mujahedeen had been exploited and cheated by the Americans and deeply resented the fact that the Saudi regime was so compliant with the U.S. agenda.

Osama became involved in the burgeoning reform movement and his attentions may never have strayed beyond the Saudi borders had it not been for Saddam Hussein's 1990 invasion of Kuwait.

Learning that the Saudis were considering asking the U.S. for help, Osama wrote a letter to the Saudi Minister of the Interior, offering to put together an army of ex-mujahedeen to liberate the tiny state. His offer was refused and shortly afterwards 100,000 U.S. troops arrived on Saudi soil.

In Osama's eyes, this was sacrilege: Saudi Arabia is home to Islam's two most sacred sites, Mecca and Medina, where the presence of non-Muslims is explicitly forbidden in the Koran. Osama described this moment to me as "the most shocking," in his life. Deeply angered and embittered, he made plans to secretly leave the land of his birth and by December 1991 had found refuge in Khartoum whence he orchestrated attacks on Saudi-based U.S. targets .

Al Qaeda had been established in 1988 and in Sudan Osama revived discussions about the group's agenda with fellow founding members, including the Egyptian Ayman al-Zawahiri. The radical drive towards globalizing jihad came from al-Zawairi who identified two battlefronts: the "near enemy," -- the Middle East's assorted tyrants and dictators (and here al-Zawahiri had form, having participated in the 1981 assassination of Egyptian President Anwar Sadat) -- and the "far enemy," -- the western powers, mainly America.

Al Qaeda's first attack on western soil came in 1993 with a truck bomb outside New York's World Trade Center that killed six and injured many more. Letters to the media (under the moniker "Liberation Army, fifth battalion") brought Israel into the equation for the first time with the group demanding that the U.S. cease all interference in the Middle East and end its "aid to Israel," as well as diplomatic ties.

The failure to find a just settlement for the Palestinians and America's perceived unconditional support for the Jewish state was another causus belli for Osama bin Laden.

In 1998, having re-established their headquarters in the Tora Bora mountains of Afghanistan where I started my story, Osama bin Laden and Ayman al-Zawahiri (among others) announced the formation of the "World Islamic Front for Jihad Against Jews and Crusaders," and launched a series of attacks on U.S. targets which culminated, on September 11 2001, with the catastrophic destruction of the twin towers, the attack on the Pentagon and the deaths of more than 3,000 people. The rest, as they say, is history.

The opinions expressed in this commentary are solely those of Abdel Bari Atwan.