Here's a look at the life of al Qaeda leader Ayman al-Zawahiri.
Birth date: June 19, 1951
Birth name: Ayman Muhammad Rabi al-Zawahiri
Father: Rabie al-Zawahiri, professor of pharmacology
Mother: Umayma al-Zawahiri
Marriages: Unknown publicly
Children: Unknown publicly
Education: Cairo University medical school, 1974; master's degree in surgery, 1978
Acted as Osama bin Laden's personal physician.
Al-Zawahiri comes from a distinguished Egyptian family. His grandfather, Rabia'a al-Zawahiri, was an imam at al-Azhar in Cairo. His great-uncle, Abdel-Rahman Azzam, was the first secretary of the Arab League.
The U.S. State Department is offering a reward of up to $25 million for information leading directly to the capture of al-Zawahiri.
Believed by investigators to have played an important role in the September 11th attacks.
1970s - Al-Zawahiri and the Egyptian Islamic Jihad work to overthrow Egyptian President Anwar Sadat and establish an Islamic state.
1980s - Joins the Mujahedeen who are fighting Soviet forces occupying Afghanistan.
1981 - Egyptian President Anwar Sadat is assassinated and al-Zawahiri is arrested. He is convicted on weapons charges, but not for being part of the assassination plot, and sentenced to three years in prison.
1987 - Al-Zawahiri and Osama bin Laden meet.
August 6, 1998 - A fax from al-Zawahiri's group is sent to an Egyptian newspaper saying that the Islamic Jihad is seeking revenge against the U.S. for the arrest of several of its members.
August 7, 1998 - Suicide bombers attack the U.S. embassies in Kenya and Tanzania.
1998 - The Egyptian Islamic Jihad and al Qaeda merge. Al-Zawahiri and bin Laden announce the formation of the World Islamic Front for the Jihad against the Jews and the Crusaders.
June 1999 - Al-Zawahiri is indicted, along with Osama Bin Laden, by the U.S. for the 1998 U.S. Embassy bombings in Kenya and Tanzania.
1999 - Receives a death sentence, in absentia, from an Egyptian court, for an alleged plot to bomb the U.S. embassy in Albania.
December 2001 - Al-Zawahiri's wife and three of his children are killed in a U.S. attack on the family's residence in Afghanistan.
January 13, 2006 - A CIA-led missile strike in Damadola, Pakistan, targets al-Zawahiri, but kills at least 18 other people.
June 8, 2011 - A video of al-Zawahiri eulogizing Osama bin Laden is released.
June 16, 2011 - Islamist websites report that al-Zawahiri is the new leader of al Qaeda.
July 27, 2011 - In a video that appears on extremist websites, al-Zawahiri delivers what is believed to be his first message since becoming the head of al Qaeda. In the video al-Zawahiri praises the anti-government protests in Syria and refers to President Bashar al Assad as "the leader of criminal gangs, the protector of traitors."
December 1, 2011 - Al-Zawahiri claims responsibility for the kidnapping of Warren Weinstein, an American citizen in Pakistan, according to a number of radical websites. Weinstein, a development consultant, was abducted August 13 from his home in Lahore, Pakistan.
March 16, 2012 - In a video posted on jihadist forums, al-Zawahiri mentions U.S. citizen Warren Weinstein, kidnapped in Pakistan in 2011. Al-Zawahiri says he will not be released until Muslim prisoners such as the "Blind Sheikh" Omar Abdul Rahman and the relatives of Osama bin Laden are released.
January 2014 - A video is posted on militant websites, in which al-Zawahiri speaks about the on-going civil war in Syria.
April 18, 2014 - A nearly hour-long interview with al-Zawahiri is posted on the radical Islamist website Hanein.
April 24, 2014 - The second part of an interview with al-Zawahiri is posted on the radical Islamist website Hanein. When asked what he'd tell "Muslims and the mujahedeen" to do to "fulfill their duty" toward their allies in custody, al-Zawahiri said, "I advise them to capture Westerners -- and especially the Americans, as much as they can -- to exchange them for our captives."
September 4, 2014 - Al-Zawahiri releases a 55-minute video, saying that al Qaeda is opening a branch on the Indian subcontinent.