I first met Qassem four years ago, at the height of the European refugee crisis. The BBC had sent me to capture the stories of Mideast migrants, thousands of whom would daily wash ashore on the Greek isles. He was around 15, malnourished and clearly traumatized. As we sat together in a cabin at a ­migrant camp on the island of Lesbos, his hunched body rocked backward and forward.

His marginal life amounted to a speck of dust amid the geopolitical earthquakes that were remaking the region at the time. Yet the story he told opened a window onto the activities of the Iranian regime and one military commander whose first name the boy shared — the late Gen. Qassem Soleimani.

I soon realized I was gathering the first evidence that Iran was sending thousands of Afghans, many of them children, to fight in the Syrian Civil War.

Qassem told me that he had been drafted into the notorious Fatemiyoun Brigade, an all-Afghan unit led by Iranian commanders under Soleimani.

Qassem — the boy, not the general — was a survivor. But he was haunted by terrors he’d experienced fighting a war he didn’t understand, for a country, Syria, that wasn’t his.

To their Iranian recruiters, the Afghan fighters in Syria were disposable. “Sometimes, we had no supplies, no water, no bread — hungry and thirsty in the middle of the desert,” Qassem told me. One night, his brigade found itself surrounded in an orchard and taking fire from rocket-propelled grenades. A friend was blown to pieces in front of his eyes.

“For nights afterwards,” he said, “I would picture my buddy in my head and would think, ‘My God, what happened to him?’ I was really scared.”

Until early 2016, Tehran ­insisted it only took an advisory role in this war, that the Islamic Revolutionary Guard Corps wasn’t involved in the activities of the Fatemiyoun Brigade. ­Everyone knew that Iran was supporting President Bashar al-Assad’s regime, but direct proof was scarce.

But now I had proof.

Over the next few days, I spoke to dozens of Afghan men and boys who had become asylum seekers in Europe. Many had been recruited from impoverished and vulnerable migrant communities in Iran to fight alongside Syrian troops.

One 17-year-old told me he had been stopped by the IRGC and asked for his identity card. This turned out to be a common ploy to press Afghans into service. The IRGC knew that, like most of the 3 million Afghans in Iran, he almost certainly didn’t possess one. So they ­issued an ultimatum: Fight for Assad and get paid $500 a month and receive an ID — or face deportation.

Within hours, he was driven to the airport in a bus with blacked-out windows and, ­despite having no passport, flown directly to Syria.

Training amounted to little more than a fortnight of tactical movement and basic weapons handling. Some of the men told me that Soleimani was a frequent visitor to the training grounds in Syria. To keep the troops in check, the IRGC told them they were fighting to protect the shrine of a Shiite saint in Damascus.

As professor Scott Lucas of Birmingham University told me, however, these boys were mere “cannon fodder” — tiny, expendable cogs in a 50,000-strong mixed militia. As well as the ­Afghans, there were Lebanese, Iraqi and Pakistani Shiite recruits. Soleimani was the mastermind of the whole cruel operation.

One of the men had an incredible escape. A Syrian family fleeing the violence befriended him, and they insisted, at great personal risk, that he was one of their kin. Together, they escaped on foot, crossing the mountainous border into Turkey and crossing by dinghy from there into the heart of Europe.

After the BBC broadcast my documentary in April 2016, the Iranian Parliament announced a bill to support the families of ­Afghan “martyrs” killed in Syria. But it also had frightening repercussions for me. Just before the program aired, my team members got scared and asked for their names to be removed. It was only my face, my name on the program, and I felt very isolated.

Human Rights Watch has since estimated that the IRGC may have recruited as many as 10,000 Afghans; up to half of them are believed to have been killed.

I never saw Qassem again. Perhaps he is living somewhere in Europe. I hope he is safe, but it remains that Afghans continue to be persecuted in Iran. Having already fled the Taliban, many end up destitute or imprisoned — or gang-pressed by the Iranian regime into fighting for a genocidal Arab dictator.

This was Soleimani’s true, hideous legacy. Don’t mourn him.

Fariba Sahraei, a former BBC Persian presenter, is senior editor at Iran International.