After his father was killed by a rocket attack in 2013 as he walked to the mosque, Syasneh said he decided to pick up a weapon and fight with the Free Syrian Army, a loose coalition of rebel groups made up mainly of army deserters.

“I lost someone dear to me, my father, who became a martyr,” he said, adding that he wanted to “carry arms to defend my land, my country, and my honor.”

As time ticked by, the conflict became more complex as foreign powers like Russia and Iran offered…