It’s no small irony President Barack Obama has initiated a military action that likely will stretch into the next presidential administration, given that he assumed office in 2009 with a mandate to end wars begun by the previous administration.

But a president’s legacy must, by necessity, take a back seat to the realities of national security. When President George W. Bush began the war on terror after 9/11, he warned that the nation would have to pursue the enemy no matter where the conflict led. The war never was figured to be quick or easy.

The question now, however, is how committed the United States will be in its effort to destroy terrorist threats. This is not the moment for the Obama administration to send mixed signals.

After hesitating because he said he lacked a strategy, the president has initiated a campaign to degrade and ultimately destroy the Islamic State militant group.

In doing so, the president has said he will not employ ground troops. Rather, he said he has assembled a group of some 40 nations — including Arab states — to lead the fight, with assistance, training and advice from U.S. and allied forces.

The problem is that while Arab nations are the ones most immediately threatened by the Islamic State, they also tend to be disorganized and militarily suspect, and they include factions with other agendas.

So, in recent days, Joint Chiefs Chairman Martin Dempsey has said he might go back to Obama and recommend using ground troops after all, if the current strategy of using air strikes and the ground forces of other nations doesn’t work.

This has led to some confusion about the scope of the U.S. mission, which was only heightened by comments from top administration officials that seemed to variously call the campaign a war and a counterterrorism operation.

Notable Republican lawmakers, such as Sens. John McCain, R-Ariz., and Jim Inhofe, R-Okla., have argued the Islamic State cannot be defeated by Arab soldiers alone.

McCain has been particularly critical of the plan to arm moderate rebels fighting against Syria’s government — rebels he said will be more interested in their own cause than in destroying the Islamic State.

While Americans may be hesitant to engage in another Middle Eastern ground war, it is safe to say the United States needs to enter this conflict with a clear objective and strategy. War generally leads to unintended consequences, and that seems an especially large risk when Arab factions, each with its own agenda in a volatile region, are doing all the fighting.

The Islamic State may not pose immediate threats to the U.S. homeland, yet. But the group clearly would like to do so. Recent videotaped beheadings of U.S. and British citizens were clear indications of intent.

It may not be possible to completely wipe terrorist enemies off the face of the earth, but it ought to be possible to minimize and marginalize them into insignificance. However, that cannot be done without an unwavering commitment. The Islamic State may be counting on the lack of U.S. resolve and clear-cut objectives to survive attacks and grow its influence. It is incumbent on this administration — not the next — to provide this effort its necessary clarity, purpose and resolve.