A man holds up a knife as he rides on the back of a motorcycle touring the streets of Tabqa city with others in celebration after Islamic State militants took over Tabqa air base, in nearby Raqqah city August 24, 2014.  REUTERS/Stringer

One of the strangest of the ways that Islamic State has forced us to rethink the Middle East is also one of the saddest: There are now common line of thought that says the United States could ally itself with the Syrian President Bashar al-Assad's regime to fight the extremist group also known as ISIS and ISIL.

"I am no apologist for the Assad regime," Ryan Crocker, a former U.S. ambassador to Syria, said last week, "But in terms of our security, ISIS is by far the largest threat." Max Abrahms, a Northeastern University professor and terror analyst, is among those who have been vocal in pushing the possibility. "Washington also needs to consider how best to protect the American population," Abrahms told The Post last week.

While it remains an unlikely possibility, the idea that the U.S. would directly work with Assad horrifies and insults many. Few doubt that his regime has committed numerous atrocities during the Syrian civil war and the idea of allying with his government at this point strikes some as absurd.

"Of all the 'stupid [expletive]' ideas, allying with Assad must be the most stupid." Aboud Dandachi, a Syrian blogger now living in Istanbul writes in an e-mail. "If he can't beat ISIS even with all the support he is currently getting, then nothing the USA can realistically do will improve his chances."

It also seems absurd given another other obvious choice that seems to be getting relatively scant attention: Working with the other Syrian opposition groups to fight both Assad and Islamic State. These opposition groups certainly don't want the U.S. to side with Assad, but they do want help fight the Islamic State and advocate a strong role for themselves.

"The Syrian Opposition fully supports a comprehensive U.S.-led campaign to launch military strikes in Syria against the Islamic State terrorist army and al-Qaeda affiliates," Oubai Shahbandar, an adviser to the Free Syria Foreign Mission in Washington D.C., explains. "The anti-Islamic State resistance on the ground is led by the Free Syrian Army and tribes."

The Free Syrian Army itself seems to advocate something even broader.

"Airstrikes against ISIS inside Syria will not be helpful," Hussam al-Marie, the spokesman for the group in northern Syria, told The Daily Beast. "Airstrikes will not get rid of ISIS. Airstrikes are like just tickling ISIS.”

Shahbandar sees intervention with Assad as absurd. "Assad was a key ingredient in the rise of the Islamic State," he says. "He and his regime turned Syria into a launching pad for terrorism over the years and fostered the environment in which transnational terrorist forces grew in the country." The argument is persuasive. Writing for the New York Times, Syrian journalist Hassan Hassan points out that the Syrian state didn't attack Islamic State-held cities with the same intensity saved for other rebel cities, and that the regime has bought oil from the group. Assad's decision to avoid fighting the group may have been driven by a desire for it to overtake the more secular groups, such as the Free Syrian Army, that were more palatable to the west.

Right now, however, its not clear exactly how plausible U.S. strikes against Islamic State within Syria would be without some kind of approval, tacit or otherwise, from Assad. The Syrian government has warned that unilateral strikes against Islamic State on Syrian soil would be seen as an act of "aggression," though it has indicated it is open to some kind of cooperation. Assad's regime has anti-aircraft capabilities and an air force which could be used to hinder any U.S. intelligence gathering or strikes in Syria. Another factor is Russia, a prominent supporter of the Assad regime, which has also voiced criticism.

Joshua Landis, director of Center for Middle East Studies at the University of Oklahoma, argues that a key problem is that the more secular rebel groups don't have the support they would need to actually control Syria.

"They're great. I like them all," Landis says of the Syrian Opposition Coalition, "[but] if you can put those people in power in Syria, you've really pulled off a coup." Landis also argued that many of the other Islamist groups in the country have similar sectarian, anti-Shiite views as Islamic State. Speaking of Hasseen Aloosh, the political leader of Islamic Front recently singled out by former U.S. Ambassador to Syria Robert Ford, Landis says he is " no different than ISIS, really, except he's a Syrian."

Ultimately, Landis argues that the only way for the U.S. to truly destroy the Islamic State and the sectarian extremism it espouses would be to offer some kind of two-state solution for Syria, or get involved in extensive (and extremely expensive) state building exercise. There's little political support in the U.S. for either. Instead, Landis suspects the U.S. will likely end up "mowing the lawn" with the Islamic State – a reference to the Israeli policy for keeping Hamas weak with periodic and limited strikes. It's a policy that may be far more acceptable than working with Assad and more practical than a wider intervention, but it won't necessarily be any more successful.