The New York Times reports: The kidnappings, which were carried out by different groups of fighters jousting for influence and territory in Syria, became more frequent. In June 2013, four French journalists were abducted. In September, the militants grabbed three Spanish journalists.

Checkpoints became human nets, and last October, insurgents waited at one for Peter Kassig, 25, an emergency medical technician from Indianapolis who was delivering medical supplies. In December, Alan Henning, a British taxi driver, disappeared at another. Mr. Henning had cashed in his savings to buy a used ambulance, hoping to join an aid caravan to Syria. He was kidnapped 30 minutes after crossing into the country.

The last to vanish were five aid workers from Doctors Without Borders, who were plucked in January from the field hospital in rural Syria where they had been working.

At gunpoint, Mr. Sotloff and Mr. Abobaker were driven to a textile factory in a village outside Aleppo, Syria, where they were placed in separate cells. Mr. Abobaker, who was freed two weeks later, heard their captors take Mr. Sotloff into an adjoining room. Then he heard the Arabic-speaking interrogator say in English: “Password.”

It was a process to be repeated with several other hostages. The kidnappers seized their laptops, cellphones and cameras and demanded the passwords to their accounts. They scanned their Facebook timelines, their Skype chats, their image archives and their emails, looking for evidence of collusion with Western spy agencies and militaries.

“They took me to a building that was specifically for the interrogation,” said Marcin Suder, a 37-year-old Polish photojournalist kidnapped in July 2013 in Saraqib, Syria, where the jihadists were known to be operating. He was passed among several groups before managing to escape four months later.

“They checked my camera,” Mr. Suder said. “They checked my tablet. Then they undressed me completely. I was naked. They looked to see if there was a GPS chip under my skin or in my clothes. Then they started beating me. They Googled ‘Marcin Suder and C.I.A.,’ ‘Marcin Suder and K.G.B.’ They accused me of being a spy.”

Mr. Suder — who was never told the name of the group holding him, and who never met the other hostages because he escaped before they were transferred to the same location — remarked on the typically English vocabulary his interrogators had used.

During one session, they kept telling him he had been “naughty” — a word that hostages who were held with Mr. Foley also recalled their guards’ using during the most brutal torture.

It was in the course of these interrogations that the jihadists found images of American military personnel on Mr. Foley’s laptop, taken during his assignments in Afghanistan and Iraq.

“In the archive of photographs he had personally taken, there were images glorifying the American crusaders,” they wrote in an article published after Mr. Foley’s death. “Alas for James, this archive was with him at the time of his arrest.”

A British hostage, David Cawthorne Haines, was forced to acknowledge his military background: It was listed on his LinkedIn profile.

The militants also discovered that Mr. Kassig, the aid worker from Indiana, was a former Army Ranger and a veteran of the Iraq war. Both facts are easy to find online, because CNN featured Mr. Kassig’s humanitarian work prominently before his capture.

The punishment for any perceived offense was torture.

“You could see the scars on his ankles,” Jejoen Bontinck, 19, of Belgium, a teenage convert to Islam who spent three weeks in the summer of 2013 in the same cell as Mr. Foley, said of him. “He told me how they had chained his feet to a bar and then hung the bar so that he was upside down from the ceiling. Then they left him there.”

Mr. Bontinck, who was released late last year, spoke about his experiences for the first time for this article in his hometown, Antwerp, where he is one of 46 Belgian youths on trial on charges of belonging to a terrorist organization.

At first, the abuse did not appear to have a larger purpose. Nor did the jihadists seem to have a plan for their growing number of hostages.

Mr. Bontinck said Mr. Foley and Mr. Cantlie had first been held by the Nusra Front, a Qaeda affiliate. Their guards, an English-speaking trio whom they nicknamed “the Beatles,” seemed to take pleasure in brutalizing them.

Later, they were handed over to a group called the Mujahedeen Shura Council, led by French speakers. [Continue reading…]