By Karl Vick
October 9, 2014

Publicly identified for the first time in late September when the U.S. launched air strikes against its positions in Syria, the Khorasan group was “working on an effort to attack the U.S. or our allies, and looking to do it very, very soon,” according to FBI Director James Comey. As more information emerges, we learn that it may not be so new after all.

Why you never heard of them before

The group is tiny, perhaps a couple dozen people, and until President Obama targeted it with cruise missiles on Sept. 23, it had managed to stay under the radar. Khorasan did not tweet. It had no YouTube channel. In the constellation of armed groups operating in Syria, it was the dark star. Even today, its actual name remains unknown, if it has one. Khorasan is the label U.S. intelligence officials say they agreed on, the ancient name for a region that includes parts of Afghanistan, Turkmenistan and Iran and that some say the Prophet Muhammad predicted would produce a triumphant army under black flags.

Who they are

In two words: al-Qaeda. The leader reported killed in the strikes, Mohsin al-Fadhli, was a senior al-Qaeda operative who the U.S. says was one of the few to know about the 9/11 attacks in advance. He was likely dispatched to Syria by al-Qaeda’s leader Ayman al-Zawahiri in early 2013 to negotiate an alliance between al-Nusra Front, which is formally aligned with al-Qaeda, and ISIS, which began as al-Qaeda in Iraq. Instead, the groups ended up at odds, with some al-Qaeda delegates joining ISIS and al-Nusra sheltering the rest.

Why they are in Syria

It’s safer there, for one thing. Predator drones have made Pakistan’s frontier a killing ground, while Syria was a place Obama had been long reluctant to bomb. Syria is also crowded with hundreds of young jihadis from Western countries who might be recruited for the terror attacks that remain al-Qaeda’s priority. “The ability to plot in relative safety is a long-term danger to us,” says former U.S. counterterrorism official Daniel Benjamin. “I can’t underscore enough how critical the safe-haven issue is.”

How dangerous are they?

Very, say experts. Syria offers al-Qaeda not only the operational freedom it enjoyed in Afghanistan before 9/11 but also far easier access to the West, by way of Turkey, a transit-and-logistics route for militant Islamists even before Ankara turned a blind eye to foreign fighters entering Syria. U.S. officials say explosives experts from al-Qaeda’s busy Yemen affiliate were working with Khorasan, attempting to create a bomb that could be slipped through airport security. Al-Fadhli had a record of financing terror projects through wealthy donors in the Gulf. “Especially for something small, one or two or three of those, you’re good to go,” says Matthew Levitt, a former U.S. Treasury official.

What might be next

If the group was not undone by the Sept. 23 strike, such a chance is unlikely to come again soon. The Americans had both tactical surprise–catching the militants in villas near the Turkish border–and apparently excellent intelligence, perhaps gleaned from former captives, says an individual involved in hostage negotiations. Further strikes may also risk driving ISIS and al-Nusra together. But with both the CIA and al-Qaeda drawing down their forces on the Pakistan border, Syria looks more and more like their new battleground.

Contact us at editors@time.com.

This appears in the October 20, 2014 issue of TIME.

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