Football fields: A waystation en route to the Islamic State

One thing the biographies of Jihadi John, the Islamic State's executioner of foreign hostages, and several of his European associates have in common is their passion for football and their dashed hopes of becoming professional players.

They all belonged to amateur teams or bonded in part by playing football together. Like other disaffected youth for whom playing football became a stepping stone to joining a militant group or becoming a suicide bomber, Jihadi John and his mates traversed football fields on their journey. Their biographies highlight football's potential as a recruitment and bonding tool.

Identified as Mohammed Emwazi, Jihadi John - a Kuwaiti-born Brit reviled for videos featuring him as the hooded killer of the Islamic State's foreign, non-Arab hostages - dreamt as a child of kicking balls rather than chopping off heads. "What I want to be when I grow up is a footballer," he wrote in his primary school yearbook. He believed that by the age of 30 he would be "in a football team scoring a goal."

In secondary school, Emwazi played football matches with five players in two teams whose members went on to become jihadists, The Guardian quoted one of the group's members as saying in evidence presented to an English high court in 2011.

The court case, which related to a control order imposed on one of three of the former players whose movements were legally restricted, Ibrahim Magag, identifies 10 to 12 men, most of East African or South Asian descent, as members of the same group as Emwazi. Four of the men attended the same secondary school. Several travelled to Somalia for training before returning to the U.K. as recruiters.

The control orders barred the three men from living in London. The orders were later...