HERAT, Afghanistan — One woman here in the western Afghan city of Herat said she had begged her son not to go fight in the Syrian war, but he charged off anyway, leaving a wife and three children behind. A man overhearing her story came over to say that his son had left two months ago, and since then the family has been desperate for news about him.

Another woman, Khadija, whose son Hassan had joined Afghan brigades fighting alongside the Syrian government, said he had been pulled into the vicious conflict for the same reasons most of the young men in the neighborhood had decided to go: “He could not find work,” she said.

A teenager standing on the edge of the group, listening to the parents, said those were hardly isolated stories among the Afghan Shiites of Herat. The neighborhood, he said, “is full of them.”

Afghanistan has been hollowed out as its citizens have fled poverty and war, many seeking work in Pakistan, Iran or Persian Gulf nations, or risking the perilous trail to Europe. But this specific emigration pattern — of thousands of young men flowing into neighboring Iran and then on to fight alongside the Syrian government and its allies — has provoked extraordinary anguish for families here and for Afghanistan’s government, particularly over the past year.