American-born cleric Anwar al-Awlaki was a high-profile al-Qa'ida terrorist with links to the September 11 terror attacks, the failed Christmas Day "underwear" bomb plot and the foiled East Midlands Airport cargo plane bomb plot.
Born in New Mexico to Yemeni parents, al-Awlaki had not been charged with any crime, but the radical Muslim cleric was wanted dead by US President Barack Obama for his links to a host of terror plots.
US officials released detailed intelligence to justify the killing of an American citizen.
Most recently, al-Awlaki was identified as a central figure in the failed East Midlands Airport cargo plane bomb plot.
But the notorious cleric has also been linked with the September 11 attacks in 2001, the shootings at Fort Hood in November 2009 and, that same year, the failed Christmas Day "underwear" bomb plot involving a British-based student.
A long line of recruits have also claimed to have been inspired to Islamist militancy through the cleric's overt endorsement of violence as a religious duty.
His sermons and outbursts on the internet have won him a legion of extremist supporters.
Al-Awlaki was born in 1971 in the US state of New Mexico, where his father Nasser, a future Yemeni agriculture minister and university president, was studying agricultural economics.
He lived in the US until the age of seven, when his family returned to Yemen.
During four years living in San Diego in the late 1990s, he took charge of the city's Masjid Ar-Ribat al-Islami mosque and his sermons were attended by two future September 11 hijackers, Khalid al-Midhar and Nawaf al-Hazmi.
In early 2001, he moved to the Dar al-Hijrah mosque in Falls Church, Virginia, which was also attended by a third hijacker, Hani Hanjour.
The 9/11 Commission found the connections suspicious, but FBI agents who interviewed him said they doubted he knew of the plot.
In 2002, he arrived in the UK but, unable to support himself while giving a series of popular lectures to Muslim youths, he returned to Yemen in early 2004.
He was detained in 2006 by the Yemeni authorities, reportedly on charges relating to a plot to kidnap a US military attache.
Since then, al-Awlaki's messages have been increasingly overtly supportive of violence.
He has been known to give religious advice by email and incited violence in a number of texts via his website, his Facebook page and many booklets and CDs, including one called "44 Ways to Support Jihad".
Such materials have been found in the possession of several convicted militants in the UK and US.
He again hit the headlines in January last year when US officials said he might have met London-based Nigerian student Umar Farouk Abdulmutallab, who was receiving his final training ahead of his alleged suicide mission.
Al-Awlaki later acknowledged that he had "communications" with the Nigerian in late 2009, but denied any role in the alleged attack.