LONDON -- The unmasking of Islamic State militant "Jihadi John" as a London man who had repeatedly been questioned by security services sent shock waves through Britain on Friday, with Prime Minister David Cameron stepping in to defend British spycraft.
Cameron tried to defuse criticism of Britain's security service, which had the man on its list of potential terror suspects for years but couldn't prevent him from traveling to Syria, where he has played a prominent role in grisly beheading videos.
Cameron did not mention "Jihadi John" or refer to his real identity: Mohammed Emwazi, a Kuwaiti-born computer science graduate raised and educated in Britain. But he said the country's spies make "incredibly difficult judgments" daily about how to pursue threats to national security and have broken up plots that would have caused immense damage.
Emwazi had been known to British intelligence services since at least 2009, initially in connection with investigations into terrorism in Somalia.
David Anderson, who is in charge of reviewing Britain's terrorism legislation, said intelligence agencies faced a big challenge to identify real threats from "hundreds, probably thousands" of suspects.
"Perhaps they did slip up in this case, but one won't know until there's been an inquiry or a report of some kind," he told the BBC.
The case has some parallels to that of two al-Qaida-inspired extremists who murdered a British soldier in a London street in May 2013. A report by lawmakers concluded that delays and other failings by the agencies had contributed to that tragedy.
However, it is not clear what laws could have been used to prevent Emwazi from leaving Britain, since he had not been charged with any terrorist-related offenses.
Authorities were working to piece together the path to radicalization of the soccer-playing London youth, who moved to Britain from Kuwait as a small child and attended state schools in London before studying computer science at the University of Westminster.
Court documents from 2011 obtained by the BBC list Emwazi as part of a network of west London men suspected by British security agency MI5 of sending funds, equipment and recruits to al-Shabab militants in Somalia. The group included Bilail al-Berjawi, a Lebanese-British militant who was killed in a U.S. drone strike in Somalia in January 2012.
Emails that Emwazi sent to a Muslim advocacy group reveal a young man increasingly frustrated by the attentions of British spies and angry at the plight of Muslims.
Emwazi approached the group, Cage, after he and two friends were arrested and deported on a trip to Tanzania in August 2009. They said they were going on a post-university safari. But Emwazi said he was grilled by a British intelligence officer who accused him of trying to travel to Somalia to link up with terrorists there.
He said the agent, who identified himself as Nick, suggested Emwazi "work for us" before saying "life will be harder for you" if he did not cooperate. The next year, Emwazi accused British agents of preventing him from going to Kuwait, where he had a job and planned to marry.
Like many British Muslims who have become radicalized in recent years, he seemed to feel that Muslims were increasingly under attack in many parts of the world and complained to Cage of the plight of his fellow believers in Chechnya, Iraq and elsewhere.
Cage said Emwazi even changed his name in a bid to escape the attentions of the security services but was still barred from going to Kuwait. His family reported him missing early in 2013. Four months later, police told them Emwazi was in Syria, Cage said.
He appeared in an Islamic State video released in August showing the slaying of American journalist James Foley, denouncing the West before the killing. A man with similar stature and voice was also featured in videos of the killings of American journalist Steven Sotloff, Britons David Haines and Alan Hemming, and U.S. aid worker Abdul-Rahman Kassig.
Foley's parents in Arizona expressed surprise that "Jihadi John" was an educated man who had real prospects in life.
"So he, in a sense, had a privileged upbringing, so to me that makes that even more sad that he'd want to use his gifts for such evil and such hatred. It's very frightening to me," Diane Foley said.
President Barack Obama's administration pledged Friday to kill or capture the militant.
Attorney General Eric Holder said on CNN that the U.S. "wouldn't put anything off the table," including sending military troops, to find the man.
"Anyone involved in the killing of American citizens will be held accountable," Holder said.
Information for this article was contributed by Jovana Gec and Astrid Galvan of The Associated Press and by Toluse Olorunnipa and John Walcott of Bloomberg News.
A Section on 02/28/2015