Here’s what could happen if NATO invaded ISIS territory

This would be difficult and costly. But it is perhaps the only path to long-term solutions of both the Syrian refugee crisis and the threat of ISIS.

No options are good, but, as someone who researches terrorism and insurgency, I believe this is the least bad alternative, and will give all relevant regional and international actors something they want.

Diplomacy won’t stop ISIS

Recent talks in Vienna, which some have hailed as significant progress, may help end the Syrian civil war. But diplomacy will not eliminate ISIS.

Representatives of 19 outside powers, including the United States, Russia, Saudi Arabia, and Iran, agreed to table their disagreement over President Bashar Assad’s role in Syria’s future, and call for a ceasefire beginning in January.

Representatives of the Syrian government and some opposition groups—but not ISIS and al-Qaida, or other terrorists identified by Jordan—would then set up a transitional government. The plan is to draft a new constitution and hold elections in 2017.

However, even if the future unfolds exactly as the optimistic diplomats hope—they are able to overcome the sticking point of Assad’s future, the ceasefire holds, all non-ISIS rebel groups are pacified, elections are held and all parties honor the results—the threat of ISIS will remain.

ISIS wants an Islamic State on their terms, not the opportunity to run candidates in a pluralistic Syrian election.

Why eliminating ISIS’ “state” is necessary

Recent ISIS-linked attacks in Ankara, on a Russian passenger jet over the Sinai, in Beirut, and in Paris demonstrate that the danger is not contained within Iraq and Syria. Additionally, the related refugee crisis has strained countries throughout the Middle East and Europe. These interconnected problems are not solving themselves.

ISIS is different from other terrorist groups because of its “state.” It’s not a real state, but they do control territory. That territory provides them with oil and other revenue sources, a place to train and plan attacks, and a location to which recruits can travel.

Controlling territory also drives recruitment.

Amplified by ISIS’ sophisticated propaganda operation and social media presence, the self-styled Islamic State signals to jihadist sympathizers worldwide that they can join a winner. For the more apocalyptically minded, ISIS’ “state” fits the prophesy of a final confrontation between a new caliphate and the nonbelievers. One of ISIS’ biggest strengths is its brand, and its brand is strong because of its “state.”

Denying ISIS any territorial control is necessary to defeat it. This would not eliminate groups in the Sinai, Libya, Nigeria, Afghanistan, and elsewhere that pledged loyalty to ISIS. But it would reduce their unifying sense of purpose and associated recruitment.

It is true that invading ISIS’ central territory would not address the reasons that disaffected individuals around the world choose to travel and fight with ISIS, or remain home and attempt terrorist attacks in support. Even worse, it could motivate them, at least in the short term.

However, as long as ISIS controls up to 50% of Syria and 30% of Iraq, it will be able to inspire followers, draw recruits, terrorize local civilians, threaten outside countries, and prevent any diplomatic settlement to the Syrian civil war.

What it will take

The only way to deny ISIS control of any territory is an invasion and occupation by a coalition of outside powers.

The air campaign initiated by the U.S.-led coalition in August 2014 will not defeat ISIS, mostly because it lacks the ground forces to take and hold territory.

The Kurdish Peshmerga retook some territory with assistance from the air, including the northern Iraqi city of Sinjar. However, given Kurdish capabilities and interests, they would not be able to hold much territory outside of Iraqi Kurdistan.

The Iraqi military didn’t stop ISIS’ advance through Sunni Arab areas of Iraq, and is having trouble retaking cities closer to Baghdad, such as Ramadi. Iranian-backed Shia militias have helped defend Baghdad and southern Iraq, but are widely rejected by Iraqi Sunnis. No local force appears capable of taking and holding Mosul, Iraq’s second-largest city, which ISIS captured in June 2014.

And that’s just Iraq.

ISIS also controls much of northeastern Syria. There are no local ground forces capable of clearing out ISIS fighters, let alone preventing them from reemerging.

The Syrian government of Bashar Assad, backed by Iran and Russia, has been locked in a fight with non-ISIS rebel groups. Having failed to defeat those rebels, they’re not going to provide the ground forces to retake ISIS-held territory in Syria, even if the Vienna diplomacy succeeds.

Significantly, in October, the United States abandoned its effort to train moderate Syrians to fight ISIS. The U.S. spent eight years training the 250,000-strong Iraqi military that failed to hold off ISIS’ advance. There’s no reason to believe America can build a force of Syrians capable of capturing and holding northeastern Syria.

That leaves outside powers. Only a sustained ground commitment from an international coalition can clear ISIS fighters from Syria and Iraq, and guarantee security long enough to gain the trust of the population and build the institutions for long-term stability.

A useful precedent can be found in the 2006-2007 Sunni Awakening. The Awakening, along with the American troop surge and emphasis on counterinsurgency, brought more stability to Iraq than at any time since the fall of Saddam Hussein.

Unfortunately, these gains did not last, because the Shia-dominated government in Baghdad did not reach political accommodation with the Sunnis of the Awakening movement. Many Iraqi Sunni Arabs, fearing persecution from a sectarian Iraqi government, accepted ISIS as the less bad alternative.

To prevent something similar from happening, NATO should aim to create semiautonomous regions controlled by Sunni tribal leaders under restored Syrian and Iraqi sovereignty, using Iraqi Kurdistan as a model.

Some benefit for everyone

To initiate this strategy, France should invoke Article 5 of the NATO charter, which declares an attack on one an attack on all. Additionally, they could seek an authorizing resolution from the UN Security Council. Both provide legal justification and would help ensure a multilateral effort.

NATO should then secure Turkish participation, along with troop commitments from member states. Next, representatives of the alliance should coordinate with other militaries participating in the region to avoid accidents and craft a cooperative strategy.

One option: Russia, Iran, and the Syrian government take the lead defeating non-ISIS rebels excluded from diplomatic talks, effectively continuing their current operations. Meanwhile, NATO, Kurdish and Iraqi forces focus on ISIS.

Though difficult, this plan could succeed because, in addition to weakening ISIS, all parties get something they want.

• Vienna conference participants would increase the chances of a diplomatic solution to the Syrian civil war, since ISIS is the largest potential spoiler.
• The EU, Turkey, Lebanon, and Jordan would all get relief from the flood of refugees, as civilians would no longer need to flee ISIS, and some could even return home to stabilized areas of Iraq and Syria.
• Russia would retain its military bases and influence in Syria.
• Iran would ensure the survival of the Syrian and Iraqi governments.
• The Kurds would maintain their autonomy, perhaps with slightly expanded territorial control.
• Iraqi Sunni Arabs would get some autonomy from the central government in Baghdad.
• The Shia-dominated Iraqi government would regain sovereignty over all of Iraq.
• Finally, the United States and France would ensure a multilateral, legally recognized campaign to eliminate ISIS, rather than the half measures both have pursued thus far.

Diplomacy is essential to a long-term solution to the Syrian civil war. But someone needs to take over ISIS’ territory, and local forces cannot do it alone. President Obama should reconsider his refusal to contribute ground forces. If he won’t, additional American advisers, special operations forces, air strikes, and intelligence could help troops from other NATO countries and local actors defeat ISIS and reach a lasting solution.

Nicholas Grossman is a lecturer in international relations at the University of Iowa. This piece was originally published on The Conversation.