The president announced a campaign to destroy the Islamic State.

This is welcome after the willful indifference the president has exhibited to the rise of the Islamic State and the fate of Iraq and Syria for years. But it would be more credible if President Obama could bring himself to acknowledge his profound error in “ending” the Iraq War — i.e., abandoning Iraq to its worst instincts and actors when he was bequeathed a fragile stability there. And if he weren’t so determined to circumscribe the anti–Islamic State campaign, comparing it to the highly limited, terrorist-plinking campaigns in Somalia and Yemen.

Strip away the stalwart rhetoric, and what the president described is a continued small-scale bombing campaign (probably extended to Syria), coupled with another announced effort to aid Syrian rebels who are perhaps more congenial to us. He made a point of ruling out combat forces on the ground, a restriction that will likely jeopardize the success of the mission.

The extremely constricted air campaign so far has had some effect, in stopping the Islamic State’s push in Kurdistan, in liberating the Mosul Dam, and in breaking the siege of Amerli. But none of this has involved expelling the Islamic State from major population centers, which will be necessary if it is to be truly defeated. It was relatively easy to hit fixed, exposed Islamic State positions around the Mosul Dam. It is another thing to fight the Islamic State in the city of Mosul itself, and other cities in Iraq and Syria.

That will almost certainly require special operators working closely with indigenous forces on the ground. In Iraq, we will have to rely on some combination of the Peshmerga, the Iraqi army, and — importantly — local Sunni tribes. The latter will be much more welcome in the Sunni heartland, where the Islamic State is strongest, than Kurdish forces or the Shiite-dominated Iraqi army. But all these forces will presumably require vetting and advising of the sort that can’t be properly done from a distance.

This especially holds true in Syria, where the Free Syrian Army, the Kurds, and other local forces are potential allies on the ground. We have long advocated aiding the relatively moderate Syrian opposition and thought it was a mistake to abandon Syria to the Sunni extremists on the one hand and the Iranian-backed killers around Assad on the other without attempting to create a cohesive fighting force more favorable to our interests. But we aren’t romantics about the Free Syrian Army, either. It has its own extremists and its capability as a fighting force is in doubt.

We fear that a campaign exclusively from the air will mean essentially a holding pattern, which is consistent with leaks from the administration about the campaign against the Islamic State potentially taking three years — in other words, lasting beyond President Obama’s time in office and falling to his successor.

If the president’s resolve is in doubt, Congress isn’t covering itself in glory, either. The president asked Congress to authorize his program to aid the Syrian rebels. We would go further: It would be an important statement of national will, a strong signal to our allies, and an act of democratic accountability if Congress voted for military action against the Islamic State in a strong, clean authorization. Instead, Congress has been ducking, in keeping with the belief of too many of its members that their role is to carp from the sidelines without ever taking any responsibility themselves.

It is an axiom of politics that if you will the end, you must will the means. It is good that our political class, both Democratic and Republican, is demanding action against the Islamic State. What the administration has done to push the Iraqis toward a more inclusive government and to forge a small coalition of the willing abroad is commendable. But there is no substitute for America’s unstinting resolve to win this fight, and for the commander-in-chief’s total commitment. No wonder even the administration is floating the idea that the fight will have to be won by the next president.