When the first group of Syrians from a U.S.-trained force intended to combat the Islamic State crossed into their country from Turkey in mid-July, they arrived in uniform carrying M16 rifles, mortars and flak vests. But they had no expense money, little food and no clear idea of how they, just 54 men, were to do battle against the extremists.

Most had been in near-total isolation during their two months of training in Turkey and Jordan, and they wanted to see their families, many of whom had been under heavy government bombardment. And it was Ramadan, a month of fasting, so they voted to take a two-week break, according to their elected commander, a former Syrian army lieutenant colonel, Amin Ibrahim.

Disaster struck when the break was over and they were headed back to their base. On July 29, a day after U.S. aircraft had attacked an outpost of the Nusra Front, al Qaida’s Syrian affiliate, Nusra seized Col. Nedim Hassan – the commander of Division 30, the rebel unit in which the trainees were to be embedded – along with seven of his men. […]