In a documentary to be aired Tuesday night, the rebels describe their clandestine journey from the Syrian battlefield to meet with their American handlers in Turkey and then travel on to Qatar, where they say they received training in the use of sophisticated weapons and fighting techniques, including, one rebel said, “how to finish off soldiers still alive after an ambush.”

The interviews are the latest evidence that after more than three years of warfare, the United States has stepped up the provision of lethal aid to the rebels. In recent months, at least five rebel units have posted videos showing their members firing U.S.-made TOW anti-tank missiles at Syrian positions. The weapons are believed to have come from Saudi Arabia, but experts on international arms transfers have told McClatchy that they could not have been given to the rebels without the approval of the Obama administration.