“I feel like a prisoner, only not in a cage, in London," Mohammed Emwazi wrote in a 2010 e-mail to a friend. Five years later, as The Washington Post reported, Emwazi was revealed to be "Jihadi John," the Islamic State executioner who has beheaded multiple hostages in a series of widely circulated Islamic State propaganda videos.

While Emwazi was born in Kuwait, his middle-class background and academic success—he reportedly graduated from the University of Westminster with a degree in computer programming—position him within a seemingly counterintuitive frame for a foreign ISIS recruit. As Karen Tumulty notes on Twitter, "'Jihadi John' from an upscale family, as was Osama bin Laden. Both contradict thesis that radicalization about economic frustration."

How Emwazi, 27, transitioned from a student in a Western capital to a force of malice in an Islamic terror group in the Middle East will be the subject of analysis and conjecture as Western governments continue to grapple with ISIS's surprising ability to recruit on a global scale. The unmasking of Emwazi comes just one day after American authorities arrested two men who had been living in Brooklyn for allegedly plotting to join ISIS or even conduct attacks on the United States. And, earlier this week, the saga of three missing London schoolgirls who were thought to have fled the United Kingdom concluded with reports that they had crossed into Syria.

Quoting intelligence officials on Thursday, The Wall Street Journal reports that roughly "one quarter of the 20,000 foreign fighters who traveled to Syria and Iraq hail from Europe, North America and Australia." Officials add that the overwhelming majority of those Western foreign fighters are "native-born citizens rather than immigrants" and often come from affluent families.

According to The New York Times, British officials have since confirmed Emwazi's identity as "Jihadi John.​"

The Washington Post, which first broke the story, has more details about Mohammed Emwazi's biography and background .

Earlier this month, The Wall Street Journal published a report on the United Kingdom's recently enacted Counter-Terrorism and Security Act, which aims to stem the flow of foreign fighters back into the country.

The Atlantic's cover story on the Islamic State provides more context on its mission and recruitment tactics.