In his address to the nation almost two weeks ago, President Obama promised to use force against the armies of Islamic State "wherever they are," and he specifically mentioned Syria. But Monday night's airstrikes in that country came sooner and with more force than expected, targeting not only Islamic State but also the Khorasan Group, an Al Qaeda offshoot thought to be plotting attacks on Americans. 
 
 This major offensive raises questions about whether the United States (and a few Arab allies) are planning a prolonged air campaign in a country whose leadership did not invite intervention. Coupled with his successful lobbying of Congress to spend hundreds of millions of dollars to train supposedly moderate Syrian rebels, the airstrikes mark a major reversal for Obama. 
 
 Until recently he has assiduously resisted American entanglement in Syria's civil war, and for good reason. The conflict pits President Bashar Assad, a secular dictator with innocent blood on his hands, against an assortment of opponents whose division into moderate and extremist factions isn't nearly so neat or stable as some advocates of U.S. intervention suppose. 
 
 Obama changed his mind about intervention in Syria for the same reason he decided to launch airstrikes in Iraq and augment the U.S. military presence in that country: a sickeningly swift sequence of events in which Islamic State fighters routed Iraqi forces, terrorized Christians and other minorities and seemed poised to attack Baghdad. Obama also was influenced, understandably, by the horrific beheadings of two American journalists. 
 
 The result was his promise of a long-term campaign to "degrade and ultimately destroy" Islamic State. Obama said that wouldn't require U.S. combat forces. But if the threat posed by Islamic State justifies a rethinking of Obama's aversion to intervention in Syria, might it not also incline him to change his view about "no boots on the ground"? Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, has said that if necessary he would recommend that U.S. military "advisors" accompany Iraqi troops into battle. 
 
 The airstrikes mark a major reversal for Obama. 
 
 We find that prospect troubling. Islamic State is a heinous group, a threat to U.S. interests (though not, as far as we know, to the U.S. homeland) and a threat to the rights of those in the Middle East whom it despises as infidels. But is the threat serious enough to justify an ever-escalating role for the U.S. military in Syria and Iraq? Does the U.S. have a clear strategy and achievable aims? The case has yet to be made. 
 
 Follow the Opinion section on Twitter @latimesopinion ||||| The initial bombing raids on Islamic State targets in Syria Monday night mark a welcome offensive that takes the war to the terrorists who beheaded two Americans and threaten U.S. interests in the Middle East and security at home. President Obama says this will be a long campaign, and it will need to be given the limitations he has put on the military. 
 
 The immediate impetus for the first air strikes was to stop ISIS assaults on Kurdish civilians in the north of Syria while also hitting the Khorasan branch of al Qaeda that...
– The New York Times editorial board thinks President Obama has the US blundering into a new war with the expanded airstrikes in Syria. Before the US gets any deeper into the operation, the president should open this up for a full debate in Congress, says the editorial. It's also "puzzling" that in preparing the nation on Sept. 10 for these airstrikes, Obama said nothing about the Khorasan group that is suddenly Public Enemy No. 1. "There isn’t a full picture—because Mr. Obama has not provided one—of how this bombing campaign will degrade the extremist groups without unleashing unforeseen consequences in a violent and volatile region," says the editorial. "In the absence of public understanding or discussion and a coherent plan, the strikes in Syria were a bad decision." Agree: The airstrikes are a "major reversal" for a president who opposed intervention in Syria for so long, writes the Los Angeles Times in an editorial. Can we trust that he won't reverse himself on ground troops, too? Yes, ISIS and the Khorasan group pose threats to US interests, "but is the threat serious enough to justify an ever-escalating role for the US military in Syria and Iraq?" asks the editorial. "Does the US have a clear strategy and achievable aims? The case has yet to be made." Disagree: The Wall Street Journal editorial board not only applauds the airstrikes but thinks US ground troops should be ready to move quickly. If the mission is to succeed, and it must, they'll be needed to direct airstrikes as militants hide in populated areas. "No US President should ever start a war he doesn't intend to win, and wars rarely go as smoothly as advertised in advance," concludes the editorial. "Now that he has attacked ISIS, Mr. Obama must show that America is the strong horse."