The Islamist al-Shabab militia commander Abdukadir Mohamed Abdukadir, alias Ikrima, was the target of the US raid on Somalia on 5 October.
Until the commando raid, which failed to capture him, even seasoned observers of Somalia's conflict had not heard of Ikrima.
He is a Kenyan citizen of Somali origin, one of many Kenyan Somalis and other foreign fighters who have joined the militia.
A friend, who asked not to be identified, told the BBC he used to hang out with Ikrima in the Nairobi suburb of Eastleigh, known as Little Mogadishu.
He said Ikirma's family were middle class and had come to live in Nairobi from Kenya's port city of Mombasa.
The two teenagers used to chew the mild stimulant khat and smoke marijuana together before Ikrima left in 2004 to seek asylum in Norway, he said.
Hubble bubble smoker
But he was unsuccessful and the BBC learnt that in early 2007 Ikrima some spent time in the UK.
The BBC's East Africa correspondent Gabriel Gatehouse says that little is known of his time in Britain.
He did spend time in London and was particularly fond of the shisha bars on Edgware Road where he would smoke the hubble bubble pipes, our reporter says.
It is not known where Ikrima was radicalised, but his Eastleigh friend, who was separately recruited by al-Shabab in Kenya, next met Ikrima in the Somali capital, Mogadishu, in 2008.
He, too, had joined the Islamist group, which is linked with the al-Qaeda network.
"When I met him, I saw that he had changed. We used to play, we used to hug each other, whenever we met, [now] there was nothing like that," the friend told the BBC.
He said Ikrima was never "on the battle ground, never on the frontline".
"The guy was a strategist. He plans. He plans so extreme that, you know, those with him they say: 'Oh, that is too much, Ikrima.'"
Residents of Barawe, the town where the US commando raid took place, agree that Ikrima seemed to be a leader in the militia with responsibility for logistics.
He is usually accompanied by about 20 well-armed guards, they say.
As a Kenyan-Somali, he is believed to speak Kiswahili better than Somali, and as such would be able to move freely in both countries.
Like many Islamist militants, he is also likely to speak Arabic - some Barawe residents say they initially thought he was from Libya.
"Ikrima represents an interesting crossover between al-Hijra and al-Shabab, as a Kenyan who can mingle among both the Somalis and the foreign fighters," analyst Matt Bryden told the Washington Post.
The Kenyan-based al-Hijra group, also known as the Muslim Youth Centre, is viewed as a close ally of al-Shabab.
Our reporter says Ikrima is now thought to be a senior recruiter of foreign fighters, and a possible link between al-Shabab in Somalia and al-Qaeda in the Arabian Peninsula, based in Yemen.
Although his name was not well known until the US raid, he was mentioned in a Kenyan intelligence report last year, which was leaked to US media after last month's attack on Nairobi's Westgate shopping centre.
He was named as the lead planner of a plot sanctioned by al-Qaeda's core leadership in Pakistan to carry out multiple attacks in Kenya in late 2011 and early 2012.
Parliament buildings, the UN's office in Nairobi, as well as Kenyan military camps and an Ethiopian restaurant frequented by members of Somalia's Western-backed transitional government were among the reported targets.
Kenyan authorities say all the plots were foiled.
The leaked Kenyan intelligence documents linked him to Samantha Lewthwaite, the British widow of Germaine Lindsey, who was one of four suicide bombers who attacked the London transport system on 7 July 2005.
Pentagon spokesman George Little said Ikrima was also closely associated with Harun Fazul and Saleh Ali Saleh Nabhan, who he said "played roles" in the 1998 bombing of the US embassy in Nairobi, Kenya, and in the 2002 attacks on a hotel and airline in Mombasa, Kenya.