Abdul Aziz al-Muqrin, al-Qaeda's reputed leader in Saudi Arabia reported killed on Saturday, was a veteran of conflicts around the world.
Muqrin: Was jailed for two years in Saudi Arabia
The 31-year-old Saudi national took up the extremist cause as a teenager and is believed to have trained with fellow Saudi Osama Bin Laden.
Driven by hatred of Saudi Arabia's pro-US monarchy, he led a series of recent attacks to destabilise the country.
His group claimed responsibility for killing US hostage Paul Johnson.
Muqrin, Saudi Arabia's most wanted man, is believed to have earned his credentials as a fighter in Soviet-occupied Afghanistan.
Much later, he was involved in the Taleban's battle against US-led forces there.
Muqrin also fought in Algeria, Bosnia, and the Horn of Africa. He was captured in Ethiopia in the late 1990s while fighting alongside Somali separatists and extradited to Saudi Arabia where he was sentenced to four years in prison.
But this was cut in half as a reward for memorising the Koran.
Muqrin is believed to have been the mastermind behind a suicide bombing at a housing compound in Riyadh in November last year, which killed 17 people.
His fighters have also been blamed for a series of increasingly bloody attacks in Saudi Arabia, including a siege in Khobar last month that left 22 people dead.
Muqrin's group, calling itself the "al-Qaeda Organisation in the Arabian Peninsula" posted a video on an Islamist website last Tuesday, threatening to kill American Paul Johnson if al-Qaeda prisoners were not released from Saudi jails.
Three days later, the same group posted another video, showing that their threat had been carried out. Mr Johnson was the third American killed in Riyadh in the past
Described as a smart and brutal tactician, Muqrin was said to have lived in the Riyadh district of al-Suwaydi, home to many of Saudi Arabia's most-wanted militants.
BBC cameraman Simon Cumbers was killed and security correspondent Frank Gardner seriously injured in a drive-by shooting while working there on 6 June.