ISIS really is different. Its ultimate and obsessed-over goal, to bring on the apocalypse, makes the group impossible to reason with. It can inspire far-off individuals, people who have never been to the Middle East or met an ISIS member, to turn themselves into suicidal killers — which makes containing ISIS to Syria and Iraq impossible.

Yet for all the ways ISIS is different, it is, all told, not so unlike the many ideologically driven insurgencies and warlord-style mini-states that have come before it. Its fighters are not invincible, 10-foot-tall warriors; they've already lost 20 percent of their territory in just the past year. And the organization has basic, earthly needs: funding, territory, and a base of popular support. Those things can be taken away. The world has defeated such groups many times before, and it can defeat this one.

For all the angry rhetoric in the presidential race, there is a surprising degree of consensus on what it would take for the United States to lead the global effort to defeat ISIS. The steps to victory are difficult and numerous, but they're neither impossible nor even really unknown.

That said, there are two things up for debate, and even if the contours are obscured by campaign noise and media hype, those debates are serious and legitimately difficult. The first debate is this: how best to close a handful of well-known gaps between what America is currently capable of doing and what needs to be done in order to defeat ISIS. Those gaps are not enormous, but they are very difficult.

The second debate, more theoretical but in many ways much harder, is this: at what point American efforts to close those gaps risk backfiring dangerously, worsening the problem rather than alleviating it, and thus at what point the US is better off going slow or even accepting elements of the status quo.

No one wants to admit it, particularly not in the middle of a presidential campaign, but the hard truth is that America faces two bad choices on ISIS. Either it can adopt the high-risk, high-reward strategies necessary to wipe out ISIS, even though these strategies could fail or even backfire, perhaps catastrophically. Or the US can choose the safer path, managing and minimizing ISIS's threats without solving the problem completely, knowing this means that some number of attacks will probably continue.

Both choices are terrible. But they're the only choices that exist.

The plan: What it will take to defeat ISIS

The basic strategy to defeat ISIS, as articulated by a wide range of foreign policy analysts, as it is currently being implemented by this president, and as it is likely to be implemented by the next president, looks something like this:

In Iraq, the Iraqi military, with help from outside groups, will gradually but surely retake territory from ISIS, which is militarily much weaker.

The Iraqi government will implement reforms, already underway, to better represent Sunni Arabs. Sunni Arabs, a minority group in Iraq, have been alienated and abused by Iraq's Shia-dominated government, which gives ISIS fertile soil there.

In Syria, first a peace deal has to stop the civil war between Syrian leader Bashar al-Assad and the rebel groups.

Then the Syrian government and the rebels, no longer fighting one another, can focus on fighting ISIS. Sunni Arabs are actually the majority in Syria, but they too have been long marginalized there and will need assurances that they'll be treated fairly.

Once ISIS is wiped off the map it will go underground, becoming "just" a terror and insurgent group. The world faced exactly this before: ISIS was once called al-Qaeda in Iraq (AQI), and it fought a years-long terror campaign in mid-2000s Iraq. AQI was defeated by three things, which would need to be repeated in both Iraq and, eventually, Syria:

A 24/7 campaign of raids to capture or kill AQI officers

The Iraqi government convincing Sunni Arabs they were better off opposing AQI

Sunni Arab tribal leaders rising up to fight the terror group they'd previously tolerated or even welcomed

As all this is happening, ISIS will attempt more international terror attacks to deter the campaign against it.

Attacks that ISIS directs and conducts itself are not so different from the al-Qaeda threat, which the world has shown success at curbing through strikes to isolate the group, intelligence to track and break up plots, and security to catch any that slip through.

ISIS-inspired attacks, perhaps the greater challenge, are less deadly but harder to predict or prevent. Because these are typically "homegrown" by local citizens, they require traditional policing — enlist local communities in looking out for bad apples, keep weapons out of bad guys' hands, and so on — as well as the fuzzier tools of countering extremist ideology. As with other forms of violent crime, stopping all attacks may be simply impossible, but the right policies can substantially curb their frequency and their impact.

Eventually, if all of this goes to plan, ISIS will lose the mini-state that provides its resources (the vast bulk of its cash is from taxing and extorting the people under its control) and its base of operations and training. Its recruiting will wither. It will be driven underground in Iraq and Syria. Once there, it can be dismantled — as the world dismantled AQI a decade earlier — until it poses little threat.

The US has a role to play in virtually every step of this. Only the US can bring together all the parties for a Syrian peace deal and can pressure the Iraqi government to better accommodate Sunnis. Only the US could organize and lead the Iraqi and international coalition currently rolling back ISIS in Iraq, and only the US can organize the same in Syria. US intelligence and counterterrorism tools that played such an important role in isolating al-Qaeda and preventing its attacks can be directed against ISIS as well.

In theory, all of this is something that the world, with US help, should be able to do. In theory, all the right players, from regional governments to global powers, agree on it. And in theory the presidential candidates do as well. So what's the problem?

The gaps: Three problems that keep the world from defeating ISIS

For all the agreement on the broad contours of an anti-ISIS strategy, there are a few holes in this plan — all of them fatal, and none with an obvious solution.

1) Only a Sunni Arab force can retake ISIS's territory, but in Syria no such force exists

Anyone else would be rejected as a foreign occupier, thus increasing rather than decreasing ISIS's base of support. ISIS operates in territory that is predominantly Sunni. After several years of sectarian violence that has often veered into genocide, many Sunni Arabs understandably fear being ruled by non-Sunnis, which is why some tolerate or even support ISIS. Kurds, who are largely Sunni as well, have had tremendous successes rolling back ISIS in Syria. But ultimately, only a force of Sunni Arabs can retake Arab-majority ISIS strongholds like Raqqa, and be welcomed into the city to wipe out ISIS there. But currently no such force exists.

Obama officials understand they need Arab Sunnis to fight ISIS. But when I asked a senior administration official how they planned to recruit this force, he didn't really have an answer. And it's not clear that an obvious answer exists. Syria's Sunni Arabs are overwhelmingly preoccupied with fighting Assad, whom they see as their real enemy and the greatest threat to their families. When the US tried to recruit Arabs to fight ISIS through a Pentagon program, it spent many millions of dollars and got only a few dozen recruits, who all promptly surrendered. Syria's Sunni Arabs might hate ISIS, but it is just not their top priority, and it won't be so long as Syria's civil war between rebels and Assad continues.

2) Syria's civil war sustains ISIS, but Russia and Iran will block any real peace deal to end the war

Whether we like it or not, Russia and Iran, who both support Assad, get a vote: They are both so deeply involved in Syria's war that they have de facto veto power over any peace deal. So they need to be on board. But neither is currently willing to give up on Assad, which is necessary for any peace deal to work. It's possible that Russia is inching in that direction — Moscow can at least in theory eject Assad while preserving its interests in Syria — but Iran is the bigger problem. Iran needs Assad or someone just like in power to protect its interests in Syria. Iran has proven it will sacrifice huge sums of money and hundreds of its soldiers to protect Assad. So it currently seems inevitable that Iran will block any Syrian peace deal, and that as long as there is no Syrian peace deal, ISIS can't be defeated.

3) Once ISIS goes underground, we know what's necessary to defeat it — but there's no one to do it

If ISIS loses its mini-state, it will go underground to act primarily as a terrorist insurgency — much as it did in the mid-2000s when it was known as al-Qaeda in Iraq (AQI). The world did defeat the group in that form. But it took, along with lots of help from Sunni Iraqis, a round-the-clock effort by American intelligence and special forces teams based in Iraq to capture and interrogate AQI officers, dismantling the group piece by piece. It was a huge undertaking, and it was only possible because of the huge American military force that occupied Iraq.

This time around, there will be no such American occupation force, not in Iraq and especially not in Syria. Thus there will be no US special forces teams running nightly raids against ISIS officers, and no unblinking eye of American intelligence that can track every car bomb to the safe house that produced it. The United States is correctly averse to sending huge occupation forces back into the Middle East, knowing this would cause more problems than it would solve. But this means that once ISIS's mini-state is defeated and the group is driven underground, there will no force on the ground that is capable of adequately defeating it. Absent that, ISIS will ravage Iraq and Syria for years with insurgency and use it as a base for terror attacks there and abroad.

The real debate: How far is America willing to go to close those gaps?

Lots of people have ideas about how to fix the holes in the American strategy against ISIS. Maybe the US should impose sanctions on Iran, or even threaten covert military action against Iranian forces in Syria, to pressure the country to concede a Syria peace deal. Maybe, unable to get Russia and Iran on board for a diplomatic agreement to peacefully remove Assad, the US should find some way to dislodge him by force. Maybe the US really should send thousands or even tens of thousands of troops back into Iraq to launch special forces raids against ISIS, as it did against AQI during the American occupation of Iraq.

What all of these ideas have in common is risk. Risk that they will put Americans in greater danger, that they will strengthen ISIS rather than weakening it, and that they might not even work.

The real debate, then, is not over which ideas are best, or which presidential candidate is temperamentally best suited to implement them. Rather, the debate is over how much risk the United States should take on in its campaign against ISIS. Where is the point at which American action would be counterproductive? The point at which the US would be better served by managing the problem rather than trying to solve it?

You can see this, for example, in the debate over whether the US should send substantially more special forces to fight alongside the Iraqi army against ISIS in Iraq. On the one hand, American special forces can help hasten the collapse of ISIS's mini-state, and after that they can help conduct raids against ISIS fighters hiding out in the population. On the other, ISIS greatly desires to fight American soldiers, for both ideological and strategic reasons: It would aid ISIS recruitment and risk alienating Sunni Iraqis wary of yet another American invasion and occupation. The Americans would also become ISIS targets and if captured could feature in grisly ISIS propaganda videos.

People on both sides of that debate can argue until they are blue in the face, with opponents of American intervention citing the risks of sending US ground forces into Iraq and supporters citing the benefits. And they're both right. Their disagreement is ultimately about weighing the risks of overreacting against the risks of acting too little.

No one wants to admit this, but it's a debate with nothing but terrible choices. Republican presidential candidates argue that with just more American assertiveness and ingenuity, we can solve these problems, but what they don't want to admit is there is a very significant chance that American action will both fail to solve the problem and will in fact make it worse.

The Obama administration will argue, if implicitly, that America is better off managing the problems posed by ISIS, that Obama's cool-headed restraint and his doctrine of "don't do stupid shit" will keep us from overreacting and making things worse. What they don't want to admit is that there is a near-total certainty under this approach that the ISIS problem will persist for years and will continue to pose a threat to Americans, and indeed that ISIS attacks are all but certain to continue, even if most of them can be stopped.

It's a debate between two bad choices. Either the US can try to defeat ISIS entirely but chance making the problem worse, throwing itself into high-risk, high-reward policies knowing they could work but could also backfire catastrophically. Or the US can accept that the risks are not worth the costs and focus on minimizing and managing ISIS's threats, even if that means accepting that ISIS will survive in some form for many years, and that periodic attacks will be part of this.

No one wants to admit that's what America's ISIS debate is really about, because acknowledging the limits of our power is just not in the American vocabulary, especially in the middle of a presidential campaign when both parties are promising the moon. Our political and media system is just not built to honestly discuss a problem that is, at least in some ways, lose-lose. But that is the problem we face with ISIS, whether we admit it to ourselves or not.