This article is from the archive of our partner .

Late on Monday evening, many Americans went to bed knowing that the U.S.-led offensive against ISIS had officially expanded into Syria for the first time with a series of airstrikes against Islamic State installations. The following morning, the first rumblings emerged about another terrorist cell that had been the target of the American efforts: the Khorasan Group.

Reactions varied from bemusement to outright skepticism:

So who are these guys? The group, said to be named for a leadership council within al-Qaeda, has been described a cell of al-Qaeda veterans who were plotting an "imminent" strike on American or European targets, hence the sudden action by U.S. forces. As the Times reported:

Several officials said Khorasan had an advanced plan for an attack involving a bomb that could pass undetected through airport security systems, perhaps by lacing nonmetallic objects like toothpaste tubes and clothes with explosive material, although officials offered no details in public and did not provide specifics on how soon an attack might be carried out.

In the aftermath of the airstrikes, eight of which targeted the group, no one seems to know if the attacks had taken out Muhsin al-Fadhli, the group's supposed leader and an al-Qaeda operative. As National Security Adviser Susan Rice told NBC:

“We can’t confirm that at this stage. We’ve seen reports on social media to that effect. We will continue to look for signs as to whether or not that’s, in fact, the case.”

What also seems to be a matter of conjecture is just how serious the threat was considering that this was a group that no one had really heard of:

Secretary of State John Kerry, went the other way, suggesting the threat was intentionally downplayed before this week.

To be fair, there are roughly 1,500 different rebel groups currently operating in Syria. And plenty of them are not particularly fond of the United States.

Over at the Daily Beast, Eli Lake wrote that American intelligence officials had been tracking the group over the summer before it suddenly "went dark." He added that the group's goal of striking a major Western target may have been inspired by the ongoing rivalry between ISIS and al Qaeda, from which the former split off earlier this year.

U.S. intelligence officials have privately and publicly described al Qaeda’s relationship with ISIS as a competitive one, with both groups staking claim to the leadership of the global jihadist movement. “It’s no secret al Qaeda is in a huge competition with the Islamic State,” [al Qaeda expert Daveed] Gartenstein-Ross said, noting that a spectacular terrorist attack on a Western target is one way for al Qaeda to make inroads against ISIS. "What’s been going on is al Qaeda exercising a strategy to compete with them. And it seems like the Khorasan Group is a part of that.”

With American airstrikes now targeting both ISIS and al-Qaeda, the fear is that, in addition to bolstering the embattled Assad regime, the two groups could put aside their differences and work together again.

This article is from the archive of our partner The Wire.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.