Experts warn that the US is underestimating a greater jihadist threat than ISIS

A joint report between two Washington, DC-based think tanks concludes that the US is dangerously underestimating a jihadist group that could prove to be even more of a threat to the long-term security of the country than ISIS.

The Institute for the Study of War and the American Enterprise Institute released their report last week. It was the result of a multi-week planning group of experts, some of whom were involved in constructing the 2007 surge of US troops in Iraq.

The report stated that the Syrian Al-Qaeda affiliate, Jabhat al-Nusra, "poses one of the most significant long-term threats" of any jihadist group.

"This Al Qaeda affiliate has established an expansive network of partnerships with local opposition groups that have grown either dependent on or fiercely loyal to the organization," the report said. "Its defeat and destruction must be one of the highest priorities of any strategy to defend the United States and Europe from Al Qaeda attacks."

While the current US strategy in the Middle East is heavily focused on ISIS (also known as the Islamic State, ISIL, or Daesh), Jabhat al-Nusra (also known as the Nusra Front) is spreading its influence through groups that oppose the regime of Syrian President Bashar al-Assad.

Fighters with whom the US partners in Syria have previously been told that they must focus on combating ISIS and refrain from attack Assad's troops. But ISW and AEI pointed out that deposing Assad, a brutal leader who has been accused of massacring his own citizens, is the top priority for many rebels.

In that case, they'll align with the most well-equipped and well-funded groups that give them the freedom to fight both ISIS and Assad. In many areas, that group is Jabhat al-Nusra.

"Jabhat al-Nusra has weakened the moderate opposition and penetrated other Sunni opposition groups in Syria so thoroughly that it is poised to benefit the most from the destruction of ISIS and the fall or transition of the Assad regime," the report said.

"The likeliest outcome of the current strategy in Syria, if it succeeds, is the de facto establishment and ultimate declaration of a Jabhat al-Nusra emirate in Syria that has the backing of a wide range of non-al-Qaeda fighting forces and population groups," it continued.

ISW and AEI predicted that Jabhat al-Nusra could then become a key affiliate for the global Al-Qaeda terror network that focuses on attacking the West.

So far, it appears that Jabhat al-Nusra has been mostly focused on fighting inside of Syria. But that could be a part of a strategy to avoid scrutiny from Western officials.

"The fact that the US is focused so exclusively on ISIS means that we are ignoring a threat that is as great," Kimberly Kagan, the founder and president of ISW and one of the authors of the report, told Business Insider.

Jabhat al-Nusra is playing a "long-game," Kagan said.

"ISIS is in fact overt about its presence and Nusra is covert about its presence. Nusra's covert presence means the US hasn't focused enough on its presence," she said.

She added: "Al-Qaeda's senior leaders have had a deliberate strategy of where they host cells that are planning deliberate attacks against the West at any given moment. Because the US has deliberately targeted Al Qaeda on the basis of whether or not there are attack cells focused on the West, Al Qaeda has tried to minimize the footprint of these cells in areas where it actually wishes to see long-term success. Syria is the top priority for Al Qaeda."

Other experts, however, have characterized the potential threat from Jabhat al-Nusra in less dire terms.

Fred Hof, a senior fellow at the Atlantic Council and former special adviser for transition in Syria under then-Secretary of State Hillary Clinton, agreed that Nusra's resources have attracted many anti-Assad rebels to the group's ranks. But he contended that these fighters aren't very interested in broader operations.

"Absent a specific focus on fighting the Assad regime I think it will be difficult for the Nusra Front to exist in any meaningful way in Syria, thereby making it difficult for the group to use Syria as a launching pad for global operations," Hof told Business Insider.

Hof also pointed out that the US could potentially lure these Nusra recruits back to moderate opposition groups if the moderate groups had resources comparable to Nusra's.

Still, Kagan warns that groups like Nusra the intent to attack the West in the future "whether they're actioning that intent right now or not."

"US policymakers are underestimating Jabhat al-Nusra because Jabhat al-Nusra wishes to be underestimated," Kagan said. "... We are so focused on ISIS that we are not looking at the second threat."

And defeating ISIS could unintentionally strengthen Nusra.

Both ISIS and Nusra are Sunni terrorist groups. ISIS has presented itself as a group that can protect Sunnis against the Assad regime, which is aligned with Shiites. Once ISIS is gone, Nusra could step in and assume that role.

"Defeating ISIS inside of Syria is likely to increase the capability and strength of Jabhat al-Nusra," Kagan said. "It's waiting in the wings for ISIS' demise in order to establish itself more firmly in key terrain and to present itself as the only reliable ally for the Sunni population."