ISLAMABAD, (AFP) - Ayman al-Zawahiri, the Al-Qaeda deputy leader who the Pakistani military believes it has cornered in a village near the Afghan border, is Osama bin Laden (news - web sites)'s closest aide and personal doctor.
The United States believes Zawahiri is the main strategist behind the Al-Qaeda network and terrorist group's ideologue, and has placed a 25-million-dollar bounty on his head.
"Ayman al-Zawahiri is the brain of Osama bin Laden. It was only after the two men met that bin Laden became so well known," said Egyptian Islamist lawyer Muntasser Mountasser al-Zayat, who knew him well.
Pakistani troops were planning to storm a cluster of tribal villages Friday where dozens of Al-Qaeda militants were putting up fierce resistance in what commanders believed was an attempt to protect Zawahiri.
The former leader of Egypt's fundamentalist Jihad group, implicated in the 1981 assassination of president Anwar Sadat and the massacre of foreign tourists at Luxor in 1997, often appears in video tapes at bin Laden's side.
An eye surgeon by training from a wealthy Egyptian family, the 52-year-old faces a death sentence in Egypt. He has published several books and studies on Islamic fundamentalism and has come to symbolize the radical Islamist movement.
He became involved with Egypt's radical Muslim community at a young age and was reportedly arrested at the age of 15 for being a member of the outlawed Muslim Brotherhood, the Arab world's oldest fundamentalist group.
Zawahiri was married in 1979 and trained as a surgeon in Cairo. His father was a reputed physician, while one of his grandfathers was an imam at Cairo's Al-Azhar institute, the highest authority for Sunni Muslims.
He founded the Jihad organization, and spent three years in Egyptian jails after being convicted for his role in the killing of Sadat. He was also convicted of organizing combat training camps, ordering an insurrection as well as the assassination of top officials.
Zawahiri left Egypt in the mid-1980s initially for Saudi Arabia, but soon he headed for the northern Pakistani city of Peshawar where the resistance to the Soviet occupation of Afghanistan (news - web sites) was based.
He worked as a doctor treating wounded fighters and linked up with Arab Islamic militants who came to take part in the Jihad, or holy war, against the Soviets, including bin Laden.
In the early 1990s he is believed to have lived in Europe before linking up again with bin Laden in Afghanistan. In 1998 he was one of five signatories to bin Laden's "fatwa" calling for attacks against US civilians and he began appearing regularly at the Al-Qaeda leader's side.
He is listed on the US government's indict for the 1998 bombings of the US embassies in Kenya and Tanzania, and he was sentenced to death in absentia by an Egyptian court a year later.
In December 2001, London-based Egyptian Islamist Hani al-Sibai said Zawahiri's wife, son and two daughters had been killed in a US air raid on Kandahar, Afghanistan -- but added that Zawahiri himself had survived.
"He is by nature a very calm person, from a good family, and someone who you can get along with easily," said Yasser al-Serri, an exiled former Jihad member who runs the Islamic Observatory Centre in London.
Zawahiri's goal is the foundation of a united Muslim nation, "based on the principles of the Sharia (Islamic law)", according to Serri.
Since September 11, 2001 he has surfaced occasionally in taped audio or video messages calling for attacks on the United States -- most recently on February 24 in messages on Arabic television stations.
"Bush, reinforce your security measures ... the Islamic nation which sent you the New York and Washington brigades has taken the firm decision to send you successive brigades to sow death and aspire to paradise," said a message carried by Al-Jazeera.