On Tuesday afternoon, the Pentagon confirmed that it had killed a key militant leader in Syria. Muhsin al-Fadhli, 34, was hit by an airstrike on July 8 while traveling in a convoy in Sarmada, a Pentagon statement said.

Fadhli was not a member of the most notorious militant group operating in Syria, the Islamic State. Instead, according to U.S. officials, he was the leader of the Khorasan group, a small division of al-Qaeda militants that was planning attacks on Western targets.

If a reference to the Khorasan group brings back only some dim memories, you may not be alone. Last year, the U.S. government announced that it had struck targets linked to a "Khorasan group," saying the militant group was “in the final stages of plans to execute major attacks against Western targets and potentially the U.S. homeland."

However, even the simplest elements of the story were mysterious — and despite the death of the group's leader almost a year later, we seem to know very little about it.

Khorasan refers to a historical region that encompassed northeastern Iran, southern Turkmenistan and northern Afghanistan and was established by the Sasanian dynasty, the last Persian empire before the rise of Islam. After it was overtaken by the Umayyad Caliphate, the region became part of early Islamic culture. A disputed hadith — hadiths are collected stories about the prophet Muhammad — mentions how "black banners will come out of Khorasan" in the end times, and the term has occasionally been used by modern jihadist groups, often to show that they did not come from Arab states.

Some experts disputed whether any group with that name existed in Syria. Pieter van Ostaeyen, a historian and blogger who follows jihadist movements, told WorldViews that "in all of the official Jihadi accounts I follow(ed), the name never was mentioned." There were even those who argued that the U.S. government were simply using the name to hide the fact that it was targeting Jabhat al-Nusra, al-Qaeda's official affiliate in Syria, which has been part of the fight against the Islamic State and has some popularity among moderate Syrians.

In public briefings, officials were adamant that not only was the group real, but that it was a real danger to U.S. lives and had to be neutralized. “In terms of threat to the homeland, Khorasan may pose as much of a danger as the Islamic State," Director of National Intelligence James R. Clapper Jr. said in September after the bombings.

Exactly what that threat was, or how severe it was, has never been revealed. While there were reports that the group was planning attacks on airplanes and had developed some kind of "exploding clothes," there were other signs that the threat was far from immediate. One unnamed U.S. official told the New York Times that the group's plan for Western attacks was “aspirational,” while another told Foreign Policy that it wasn't clear whether the group had the capability to carry out its attack plans.

To complicate matters further, there were reports that Fahdli was killed last year in strikes to the west of the Syrian city of Aleppo. U.S. officials would not confirm the reports. Fahdli's exact role within the group remains unclear to this day.

Some, such as the Intercept's Glenn Greenwald and Murtaza Hussain, have argued that the Khorasan group was simply a creation of the U.S. government, intended to spur support for military action in Syria. In May, the leader of Jabhat al-Nusra told Al Jazeera network that the Khorasan group didn't exist. "They claim that this secret group was set up to target the Americans, but this is not right," Abu Mohammed al-Golani said.

But perhaps the most remarkable thing about all of this is how the Khorasan group disappeared from the headlines almost as quickly as it had arrived. Since reports that it was targeted by airstrikes in  September, there has been little news or information about the group. As the Islamic State continued to make gains and commit atrocities, public interest in the Khorasan group dramatically dropped off.

Tuesday's announcement brings the group back into the spotlight for the first time in a while and does (hopefully) clear up one detail: Fadhli is really dead this time. For the rest of it, however, the public is as much in the dark as ever.

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