And that’s not a good sign, in case readers wonder. The initial air strikes in Syria ordered by Barack Obama included a number of targets near Aleppo that focused on the Khorasan group, chartered by so-called core al-Qaeda to refocus attacks on Western aviation in particular. US intelligence sources tell Eli Lake at the Daily Beast that the bombmakers of Khorasan had worked to develop non-metallic bombs, including clothing seeped in explosive compounds, that could pass through airport detection systems. In the weeks [see update] before the airstrikes, however, the terrorist group “went dark,” just as intelligence officials thought they were ready to go operational:

American analysts had pieced together detailed information on a pending attack from an outfit that informally called itself “the Khorasan Group” to use hard-to-detect explosives on American and European airliners.

As the Khorasan Group came closer to executing the attack, however, U.S. intelligence agencies lost track of the plotters. “We had some information on their plans that did not pan out over the summer,” one senior U.S. intelligence official told The Daily Beast. “They shut it down and went dark.”

Since 2012, the U.S. intelligence community has tracked the movement of several senior al Qaeda planners into Syria, where they have set up operations aimed not at Bashar al-Assad’s regime, like many of their fellow militants. Instead, these planners were focused on Europe and America. At first, the group was believed by U.S. intelligence agencies to be al Qaeda’s senior operatives and linked to al Qaeda’s franchise in Syria known as al-Nusra. But beginning in the spring, the intelligence community began to call the outfit “the Khorasan Group,” named in part because many of its members are affiliated with the Khorasan Shura, a leadership council within al Qaeda. Khorasan in Jihadist literature refers to the region that includes Pakistan, Afghanistan, and Iran.

“My suspicion is what we are hearing about Khorasan is only part of the group,” said Daveed Gartenstein-Ross, an expert on al Qaeda at the Foundation for the Defense of Democracies. “It strikes me as quite possible we are only hearing about the external operations wing and not the entire organization.”

There seems to be no good explanation yet for why they went underground. Word of their existence only began to leak out in the American media over the last few weeks, and perhaps they got spooked by the attention. Then again, it was also not exactly a surprise to see US airstrikes in Syria, with ISIS making themselves a big, fat target for reprisals with the butchering of two American journalists. They may have decided a lower profile was just a better idea for tactical purposes without having an indication that US intelligence had discovered their operations.

The other reasons could be more ominous. If they have developed a bomb that they think will pass through Western security checks, they may have shifted to an operational phase. The heightened security alerts about powered-down cell phones and laptops sprang from intelligence warnings about those efforts, and one presumes that security agents have some way to determine explosive-laden clothing when seen. But if the group went dark because their project went operational, why would their leaders have remained in place, as they seemed to have done?

Jihadist media claimed two of the group’s leaders, Muhsin al-Fadhli and Abu Yousef al-Turki, were killed in the attack. A Pentagon spokesman said he could not confirm those reports.

That would be even more curious. If the plan went operational, the leaders would have either gone with the group or returned to safer ground than Syria. That would be especially true if Khorasan has a broader organization in place elsewhere other than this operation; Fadhli and Turki would have been useful for other projects. It’s possible that the jihadist media is floating disinformation too, but given that the deaths of high-ranking terrorist leaders isn’t exactly a morale-builder for the rank and file, that seems less likely to be the case.

The danger from Khorasan may have pushed Obama over his reluctance to act in Syria. The Washington Post notes just how far Obama is pushing at the military restraints he himself established after succeeding George W. Bush as President:

After spending nearly six years of his presidency installing a series of constraints on U.S. counterterrorism operations, President Obama has launched a broad military offensive against Islamist groups in Syria that stretches the limits of those legal and policy enclosures.

The barrage of airstrikes was aimed mainly at a militant group, the Islamic State, that is no longer among the al-Qaeda “associates” envisioned by the military authorization passed after the Sept. 11, 2001, attacks. The group is not even suspected of planning attacks against the United States.

The unfolding U.S. air campaign has employed weapons — including dozens of 3,000-pound Tomahawk missiles launched from U.S. warships — that have flattened targets in ways destined to test Obama’s doctrine requiring “near certainty” that no civilians be killed. …

But overall, the initial dimensions of the assault put the United States on a significantly different counterterrorism course than Obama envisioned last year, when he delivered a speech describing the nation’s security landscape as returning to pre-Sept. 11 normalcy.

“We must define the nature and scope of this struggle, or else it will define us,” Obama said in a May 2013 speech at the National Defense University,outlining an array of new limits, including “respect for state sovereignty.”

“There are a lot of lines that he’s drawn in the sand. Just about every one of which he seems to have crossed now,” said Jack Goldsmith, a Harvard University law professor and senior Justice Department official in the Bush administration, who attributed the outcome in part to the nature of Obama’s job.

Some of those self-imposed constraints were ill advised in the first place. Significantly, though, Obama has repeatedly crossed a line that Bush didn’t, which is the rejection of Congress as a partner in his new war. An attack on Khorasan would qualify under the 2001 AUMF against al-Qaeda, but that’s not true of ISIS, especially in Syria. Bush got Congressional authorization to go into Afghanistan and Iraq, while Obama hasn’t once asked for Congressional authorization for his wars — in Libya or in Syria.

For the moment, he might reap a political benefit from the “damn the torpedoes” political approach, but it will leave him very lonely indeed if it doesn’t work out well … like it did with Libya. And with Khorasan, it wasn’t necessary to do so anyway.

Update: Eli e-mailed to clarify the timeline for me; Khorasan went dark over the summer, not immediately prior to the strikes. That makes the claims of the jihadists that Fadhli was still there even more curious, though.