Barrack Obama said about 190,000 people are now estimated to have been killed. But the death of American reporter James Foley and the gruesome video of his beheading – a “message to America” from the propaganda masterminds at the IS – appears to have prompted a shift in his thinking.

On Monday it was revealed that Obama had authorised spy planes to track militants in Syria in what is considered a precursor to possible airstrikes. That decision followed an acknowledgement last week by the Pentagon that the IS, also known as the Islamic State of Iraq and Greater Syria, or ISIS, is a greater threat to the United States than al Qaeda.

Defence Secretary Chuck Hagel described the IS threat as posing "an imminent threat to every interest" and "beyond anything we’ve ever seen” while Obama’s senior Pentagon advisor, Chairman of the Joint Chief of Staff’s Martin Dempsey, stressed that the IS would be unconquerable if Syria were left untouched.

The marked shift in tone was followed by a statement from the foreign ministry in Damascus that the United States was welcome to “combat terrorism” in the country - provided that President Bashar al-Assad is kept apprised.

Murky ground

The militants now control a territory roughly the size of the United Kingdom, stretching from Syria’s second city, Aleppo, to the outskirts of the Iraqi capital, Baghdad.

The US has already carried out some 100 airstrikes in Iraq, successfully destroying scores of armoured vehicles and more than a dozen enemy fighting positions since August 8. But the situation on the ground in Syria, where years of civil war have left large swathes of the country in bloody obscurity, remains unclear.

“In Iraq we seem to seem to have been able to find some very good targets. In Syria, the question is what exactly we are targeting,” Elliott Abrams, a Senior Fellow for Middle Eastern Studies at the Council for Foreign Relations, told FRANCE 24.

Abrams points out that successful strikes on the IS in Iraq take place when they are travelling, often in US-supplied armoured vehicles stolen from Iraqi state forces.

In Syria, where the militants have been able to flourish without fear of sophisticated air power, larger operations, such as military bases, might also be open to attack.

“IS militants are different from traditional terror groups because they don’t hide out in the desert, they control and seek to govern territory,” explains John McLaughlin, former deputy director of the CIA and senior fellow at the Brookings Institute’s Center for Middle East Policy and US Foreign Policy programme.

“By virtue of administering territory, they have to have somewhere to gather fuel; to repair equipment and to train. For now, they can do this in Syria which remains a safe haven. But once the US expands operations across the border, their structure could be their downfall.”

Dealing with Assad

The welcoming by Assad’s foreign minister on Monday of (strictly Damascus-authorised) US airstrikes in the country brought home the startling possibility of an accord with the abhorred Syrian president, years into a nebulous campaign to have him overthrown.

Many in the West point out that tackling the IS would help Assad. The group is one of the regime’s fiercest enemies: on Tuesday the severed heads of army soldiers were displayed in the IS stronghold of Raqqa following a lengthy battle to capture the al-Tabqa airbase, in which some 170 government forces were killed.

On the same day White House Press Secretary Josh Earnest said that the US has “no plans to coordinate with Syria,” dismissing demands that the Assad regime be notified of military action because the US does not recognise it as the legitimate ruler of Syria.

But circumventing Assad could be dangerous. Foreign Minister Walid al-Moualem’s proposition on Monday also came with a stark warning – that if the US were to target the IS within Syria without the regime’s consent, it would be considered an “act of aggression”.

Assad reiterated that view in an interview with US network PBS on Tuesday (to be aired on September 9), warning the US that it should “expect every action” in retaliation for any military action in Syria.

Lesser of two evils?

“Assad is not someone the US wants to work with but it’s a logical step in tackling ISIS,” Martin Knights, a Lafer fellow of The Washington Institute and specialist in military and security affairs in Iraq, told FRANCE 24. “In one of the countries IS operates in we work with the government – Iraq. In the other, we are trying to overturn it.”

Knights believes that “making peace” with Assad could lead to a cross-religious alliance of governments in Syria, Iraq and even Iran, working together to help Sunnis resist and detach from the IS, “effectively cutting the militants’ legs from underneath”.

But others are less willing to entertain the prospect of dealing with Assad. Abrams, who served as a key adviser on Middle East policy during the George W. Bush presidency, described the idea as “morally loathsome” and suggested cutting Assad out of the picture entirely. “We could either ignore him – it would be unlikely for him to protest loudly – or we could recognise a Syrian opposition government and gain consent from them to carry out the strikes,” he said.

McLaughlin believes there is a middle way.

“The US should be subtle and sophisticated enough to manage two conflicting ideas at the same time,” he says.

“Washington doesn’t need to make an alliance with Assad, but can tell him, secretly, about their plans, with as little notice as possible. Assad will accept because, firstly, he wants IS gotten rid of and second he knows that he can’t take on the US military.”

Once the IS has been dealt with, McLaughlin says, the US could then “turn its attention to Assad”.

Looking to Tehran

Looking to another of America’s sworn enemies (and in equal measures, an ally to Assad), Iran may prove indispensable in securing Syria from the ground up - something which Secretary of State John Kerry hinted at in June.

“There is certainly a common interest in blunting IS [between the US and Iran]”, says Abrams. “Perhaps it will lead the Iranians – who have troops on the ground in Syria, or indeed Hezbollah [Lebanon’s Shiite militant group] - who also have troops on the ground - to fight IS head on.”

However, Abrams rules out open cooperation between the governments of Washington and Tehran “in the near future”.

Another option would be to arm and help train moderate Syrian rebels on the ground. But Abrams is concerned that while a necessary step, it could take more than a year to follow through amid an intractable civil war.

McLaughlin agrees that there is no quick solution to curbing IS's bloody sweep. “This is a long-term project, and one not so much defeating the IS but degrading them,” he said.

A major concern in Washington is a domestic attack by the IS during the remaining two-and-a-half years of the current administration.

According to Knights, “IS certainly has the reach to attempt an attack on home soil".

Hundreds or even thousands of IS members are believed to hold European passports, meaning they can travel to the US without a visa. The group is also considerably wealthier than its predecessors, with money from oil, extortion and smuggling earning it what might be more than $2 million a day. 

“An attack on the homeland would have serious reciprocations for the administration,” says Abrams. “Obama has rejected calls long enough. There is an urgent need to do something now.”