It’s a turning point. Or at least it should be. Kurdish guerrilla fighters, aided by the Iraqi Army and American airstrikes, have managed to retake the crucial Mosul Dam from Islamic State (IS) extremists. They have delivered these bloodthirsty fanatics their first major strategic setback in many months. The fundamental vulnerability of Islamic State forces has been demonstrated. And one method by which they can be defeated, particularly by an array of different forces working together, has been successfully realized.

Indeed, the initial reports were considered by many too good to be true. Doubts were fueled by the lack of video footage demonstrating that the Dam was back under the control of Kurdish and Iraqi government forces. However, when President Barack Obama interrupted his family vacation at Martha’s Vineyard on Monday to publicly confirm the development, and defend the use of American aircraft in the fighting, virtually all doubts were put to rest.

Assuming Islamic State fighters really have been routed and their hopes of controlling the Dam are permanently crushed, the momentum must be seized. It would be almost criminally negligent to allow the Islamic State to regroup, lick its wounds and prepare to fight another day. Instead, this dramatic reversal of fortunes needs to be relentlessly built on, both on the ground and at the symbolic register of narratives.

Kurdish forces were hardly ideally suited to this task. For decades they have been focused on defending the largely mountainous regions now governed by the Kurdistan Regional Government in northern Iraq. They have become exceptionally effective and adept at doing this. However, the operation at the Dam required these fighters to project their force far beyond their normal area of operation, in very different terrain and under very different circumstances than they are used to, and to take on an offensive posture.

The support they received, particularly from punishing American airstrikes, were undoubtedly crucial to their success. But it’s still striking that Islamic State militants appear to have crumbled when confronted with a concerted military opposition. Even an unlikely and jerry-rigged combination of forces demonstrated that these extremists are highly vulnerable to any robust challenge.

That fact needs to be communicated in no uncertain terms to the Islamic State’s constituency and target audience, who often seem primed to believe that its military and political success is divinely ordained. And it needs to be reinforced by a series of additional defeats, even if they are less dramatic and indeed perhaps modest, in fairly short order.

The ultimate goal of a concerted campaign against the Islamic State must be to drive it out of Iraq, if not altogether, then at least in the main. This will obviously have to be done in stages and over time. Patience is as important as determination in such a mission. However, a combination of incentives and disincentives is urgently required to isolate the Islamic State. The Islamic State’s appeal to both its core constituency and its allies of convenience such as Sunni tribesmen and former Baathists is its reputation as an effective, if not invincible, fighting force.

That mystique, precisely, is what needs to be smashed to pieces. It has just been badly cracked. Clearly, the current moment provides a crucial opportunity to inflict further damage on this mythology.

But that’s going to require all serious parties to put their differences aside and work together, or even independently, towards the same goal. Given that, for one reason or another, it’s in all of their interests, this should certainly be possible. Acting in their own interests, Kurdish groups and the United States are now leading the battle against the Islamic State. The key missing element is the Arab world.

Arab states have an obvious and urgent interest in obliterating the Islamic State. The raison d’être of the organization, after all, is not merely to become a state to rival existing ones. That would be bad enough. Instead, it is a far more serious challenge: the Islamic State sees itself as the alternative to the existing Arab state system. Its goal is to eliminate that system altogether and replace all existing states with itself writ large.

Attitudes that may have once existed towards the Islamic State in the past, whether disinterest, ambivalence or even perhaps some vague sympathy, given that they were perceived to be fighting obnoxious regimes in Syria and Iraq, should have been dispensed with long ago. At this stage, there is simply no intelligible argument for anything other than alarm among Arab states and mainstream societies.

The Islamic State threatens everyone simultaneously. Therefore the response to it should be similarly mutual.

The process of ridding Iraq of the Islamic State cancer is probably going to be complicated and protracted. Even greater patience will be required when it comes time to confront the Islamic State in its redoubt in Syria, especially since strengthening the Bashar al-Assad dictatorship must not be a byproduct of a necessary and unavoidable campaign against IS terrorists. But none of this is beyond the ability, assuming they wish to fight back, of those targeted by the Islamic State, either at present or in some aspirational future.

The Mosul Dam defeat is likely to be a defining moment for the Islamic State. Either this will set off a chain of events that ultimately leads to its collapse, even if that’s a relatively slow process, or it’s a defeat that demonstrates the limits of the ambitions, but not the inevitable defeat, of the IS.

Arab states will play a crucial role in determining whether or not this is the beginning of the end for what is by far the most fanatical and dangerous movement in modern Middle Eastern history. They must, in simple self-defense, become part of a concerted campaign to rid the Middle East of the Islamic State, or live to rue the day.