ISIS an 'Incredible' Fighting Force, US Special Ops Sources Say

— -- With the Obama White House left reeling from the "savage" slaughter of an American journalist held hostage by ISIS terrorists, military options are being considered against an adversary who officials say is growing in strength and is much more capable than the one faced when the group was called "al Qaeda-Iraq" during the U.S. war from 2003-2011.

ISIS, the Islamic State of Iraq and Syria, has been making a "tactical withdrawal" in recent days in the face of withering U.S. airstrikes from areas around Erbil in northern Iraq and from the major dam just north of Mosul it controlled for two nail-biting weeks, according to military officials monitoring their movements.

"These guys aren't just bugging out, they're tactically withdrawing. Very professional, well trained, motivated and equipped. They operate like a state with a military," said one official who tracks ISIS closely. "These aren't the same guys we fought in OIF (Operation Iraqi Freedom) who would just scatter when you dropped a bomb near them."

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ISIS appeared to have a sophisticated and well thought-out plan for establishing its "Islamic Caliphate" from northern Syria across the western and northern deserts of Iraq, many experts and officials have said, and support from hostage-taking, robbery and sympathetic donations to fund it. They use drones to gather overhead intel on targets and effectively commandeer captured military vehicles – including American Humvees -- and munitions.

"They tried to push out as far as they thought they could and were fully prepared to pull back a little bit when we beat them back with airstrikes around Erbil. And they were fine with that, and ready to hold all of the ground they have now," a second official told ABC News.

ISIS didn't necessarily count on holding Mosul Dam, officials said, but scored a major propaganda victory on social media when they hoisted the black flag of the group over the facility that provides electricity and water to a large swath of Iraq, or could drown millions if breached.

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U.S. special operations forces under the Joint Special Operations Command and U.S. Special Operations Command keep close tabs on the military evolution of ISIS and both its combat and terrorism -- called "asymmetric" -- capabilities, officials told ABC News. A primary reason is in anticipation of possibly fighting them, which a full squadron of special mission unit operators did in the Independence Day raid on an ISIS camp in Raqqah, Syria.

"They're incredible fighters. ISIS teams in many places use special operations TTPs," said the second official, who has considerable combat experience, using the military term for "tactics, techniques and procedures."

In sobering press conference Friday, Secretary of Defense Chuck Hagel said ISIS has shown that it is “as sophisticated and well-funded as any group that we have seen.”

“They’re beyond just a terrorist group. They marry ideology, a sophistication of strategic and tactical military prowess. They are tremendously well-funded,” he said. “This is beyond anything that we’ve seen.”

Prior to ISIS’s recent public successes, the former chairman of the 9/11 Commission, which just released a tenth anniversary report on the threat of terrorism currently facing the homeland, said he was shocked at how little seems to be known inside the U.S. intelligence community about the Islamist army brutalizing Iraq as it has Syria.

“I was appalled at the ignorance,” former New Jersey Governor Tom Kean, who led the 9/11 Commission, told ABC News last week.

Kean, a Republican, who with vice chairman Lee Hamilton, a Democrat, recently met with about 20 top intelligence officials in preparation of the commission’s latest threat report, said many officials seemed both blind-sided and alarmed by the group's rise, growth and competency.

“One official told me ‘I am more scared than at any time since 9/11,’” Kean recounted in a recent interview.

A spokesperson for the Office of the Director of National Intelligence defended the intelligence community’s tracking of ISIS, saying officials had “expressed concern” about the threat as far back as last year.

“The will to fight is inherently difficult to assess. Analysts must make assessments based on perceptions of command and control, leadership abilities, quality of experience, and discipline under fire -- none of which can be understood with certainty until the first shots are fired,” ODNI spokesperson Brian Hale said.

Where did ISIS learn such sophisticated military methods, shown clearly after the first shots were fired?

"Probably the Chechens," one of the U.S. officials said.

A Chechen commander named Abu Omar al-Shishani -- who officials say may have been killed in fighting near Mosul -- is well known for commanding an international brigade within ISIS. Other Chechens have appeared within propaganda videos including one commander who was killed on video by an artillery burst near his SUV in Syria.

Earlier this year, ABC News reported on the secret history of U.S. special operations forces' experiences battling highly capable Chechen fighters along the Afghanistan-Pakistan border since 2001. In addition, for decades Chechen separatists have waged asymmetric warfare against Russian forces for control of the Northern Caucasus.

The Secret Battles Between US Forces and Chechen Terrorists

In the battle against ISIS, many within American "SOF," a term that comprises operators from all branches of the military and intelligence, are frustrated at being relegated by the President only to enabling U.S. airstrikes in Iraq. They are eager to fight ISIS more directly in combat operations -- even if untethered, meaning unofficially and with little if any U.S. government support, according to some with close ties to the community.

"ISIS and their kind must be destroyed," said a senior counterterrorism official after journalist James Foley was beheaded on high-definition ISIS video, echoing strong-worded statements of high-level U.S. officials including Secretary of State John Kerry.

But asked when the Obama administration would attempt to confront ISIS, the official declined to answer.

Ben Rhodes, the President’s Deputy National Security Advisor for Strategic Communications, told reporters Friday that Obama is currently focused on protecting American lives, “containing” ISIS where they are and supporting advances by Iraqi and Kurdish forces.

“Our military objectives in Iraq right now are limited to protecting our personnel and facilities and address the humanitarian crisis,” Rhodes said. The “ultimate goal,” Rhodes said however, was to “defeat” ISIS.

“We have to be clear that this is a deeply-rooted organization… It is going to take time, a long time, to fully evict them from the communities where they operate,” he said. “In the long term, we’ll be working with our partners to defeat this organization.”

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