“We have to be honest,” he said. “We weren’t able to finish it the way we wanted.”

MR. EID described his own journey with the kind of youthful megalomania that has produced many a revolutionary. He was born on Easter Sunday in 1987 in Damascus. According to family lore, he was the only Muslim and the only boy to arrive that day at a Christian hospital — a sign, a nurse told his mother, that he would do great things.

He and his family are Palestinians, who can live, study and work in Syria on an equal footing with locals in all but citizenship, a marked contrast with other Arab countries. That policy helped Mr. Assad claim to be the Palestinians’ champion — making Mr. Eid feel, he said, like “a living excuse for dictatorship” — but it also gave Palestinians a stake in the country, one that would lead many of them to adopt the uprising as their own.

When the anti-Assad demonstrations started in 2011, Mr. Eid avoided them at first, but he let protesters hide at his apartment when the shooting started. Security forces indiscriminately killed or arrested “smart and decent” people, he said, and local men were shooting back.

Mr. Eid, a wiry man who grew up reading Reader’s Digest in Arabic and English, called himself “a lover, not a fighter.” But eventually, he said, he felt compelled to join the rebels. During shelling he played “Iris,” by the Goo Goo Dolls, imagining the perfume of his girlfriend in Europe.

At dawn on Aug. 21, 2013, the chemical attack struck Moadhamiyeh. Struggling to breathe, Mr. Eid staggered outside, saw a young boy foaming at the mouth, and then passed out. A friend found Mr. Eid among dead bodies; after a shot of atropine, he awoke to an earthshaking bombardment.