The video executions of two American hostages have awakened this country to the sweepingly brutal campaign of the Islamic State in Iraq and Syria, but its savagery is only part of what has made the Sunni extremist group dangerous enough for the United States to commit to military action. ISIS leader Abu Bakr al-Baghdadi heads an efficient organization that is also well financed and well armed, having seized key cities and infrastructure, including oil fields that generate millions of dollars a day. It has exhibited the ability to govern in locales it has taken over and has attracted thousands of foreign recruits to a force already numbering, by some estimates, thirty thousand. It has conducted genocidal raids on Iraq’s Shiites, Kurds, Yazidis, and Christians. Its ability to inspire or carry out terrorist attacks in other countries, including the United States, cannot be ruled out.

If ISIS represents a clear and present danger, then why do the messages from Washington seem so murky? In carrying out limited air strikes in Iraq and now in Syria, and in arming and training so-called moderate insurgents, President Barack Obama is working within both the constraints he has set for himself as a reluctant warrior and those set by an American public wary of the prospect of another full-scale war in the Middle East. Yet there is concern that a gap exists between the goals defined by the president in his September 10 address—to “degrade and ultimately destroy” ISIS—and the methods proposed for achieving them. This has recently been demonstrated in comments from the chairman of the joint chiefs of staff that U.S. ground troops might be needed to defeat ISIS, calling into question Obama’s assurances that he will not send American soldiers to do what he proposes local fighters should. 

Meanwhile, in searching for a legal rationale for executive action, the administration has cited two previous congressional authorizations for use of military force: one issued in 2001, just after the 9/11 attacks, the other granted in 2002 to begin the war against the Saddam Hussein regime. Either one is a stretch: the former refers specifically to “Al Qaeda and its associates,” the latter to Iraq. As has been pointed out, ISIS is not Al Qaeda, and Syria is not Iraq. The Constitution may allow Obama to act without Congress, as he has done since August when he first ordered air strikes to save the lives of thousands of Yazidis and Kurds. But an extended military engagement should require congressional authorization, not legal subterfuge on the president’s part.

Unfortunately, Obama’s evasiveness is more than matched by the hypocrisy of Congress, which clearly wants to avoid any direct responsibility for intervention in Iraq or Syria. Before leaving for midterm elections, the House and Senate passed a relatively modest measure—appended to a spending bill—approving training and equipment for Syrian rebels. Though backed by leaders in both parties, it won mostly tepid support and was opposed by dovish Democrats, libertarian isolationists, and hawkish Republicans who protested it wasn’t strong enough. “Muddled” was the word used by the Washington Post to describe the nature of the activities on the House floor before the vote, though it could apply generally to the interaction among all of the main players in Washington.

Of course, “muddled” is the last word the world wants to hear in connection with more U.S. military involvement in the Middle East. ISIS has committed crimes against humanity; indeed, it has provided the world with video documentation of its crimes. This should be enough to justify military intervention. But it still leaves two questions: Without the backing of Congress or the United Nations, is the United States legitimately authorized to use force? And does Obama’s proposed strategy stand a reasonable chance of achieving its aims? “Degrade” and “ultimately destroy” are two very different goals. Thanks to the capabilities of the U.S. military, degrading ISIS is well within reach. But it seems unlikely that the group can be destroyed without deploying U.S. troops. While growing international support for confronting ISIS lends welcome legitimacy, other factors complicate the picture. Qatar and Saudi Arabia participated in the most recent air strikes in Syria, yet both have been sources for the financing of Islamist extremists. Turkey, fearful of empowering the Kurds, is noncommittal. Iran, while supporting the fight against ISIS, is also an ally of Syria’s Assad regime.

How the administration gathers congressional and international support over the next months will be crucial in sustaining the fight against ISIS. But it will also establish precedents that will either limit or expand presidential war-making powers for Obama’s successors, who are seemingly bound to inherit this fight and face others like it. The president has few good options, but the worst is to initiate another war in the Middle East without first securing the firm consent of the American people and their elected representatives.