Despite politically driven rhetoric touting the virtues of “going it alone” in foreign policy, cooperation with other nations in its various forms remains essential to countering terrorism. The Islamic State (also known as ISIS) may be on the run within Iraq and Syria, but its affiliates and other terrorist groups such as al Qaeda still represent a significant threat to international security. Because such groups span countries, communities, and borders, international cooperation to defeat them has been critical.

In a recent report, we used game theory and related methods to assess the likelihood of ISIS’ defeat. We found that if the international trend toward isolationism continues, ISIS’ destruction will become less likely—and as terrorism continues from al Qaeda and other groups, international cooperation will be just as relevant to ISIS’ successor. However, if countries and firms band together and share resources, they can succeed.

STRONGER TOGETHER

The benefits of multilateral cooperation against terrorism are readily apparent. The Coalition to Counter ISIS, for example, comprises 68 countries and institutions that have come together around core principles such as military cooperation, disrupting the flow of foreign recruits to and from Iraq and Syria, cutting off ISIS’ access to the international financial system, addressing humanitarian crises, and countering the ISIS brand. Such cooperation is critical to ISIS’ defeat.

Since September 2014, members of the coalition—including Australia, Bahrain, Belgium, Canada, Denmark, France, Jordan, the Netherlands, Saudi Arabia, Turkey, the United Arab Emirates, and the United Kingdom—have carried out over 19,000 air strikes against the group in Iraq and Syria. Other cooperative efforts include pooling of ammunition and providing advisers to Iraqi military components to strengthen their efforts in the theater of battle.

Blocking ISIS’ access to resources is key, since it has positioned itself as the wealthiest terrorist organization in history. By conservative estimates, between 2015 and 2016, ISIS had approximately $1.5 billion in annual revenue, largely from taxation and extortion, but also from oil and smuggling operations, the sale of antiquities, and foreign donations. In response, the international Financial Action Task Force has shared financial intelligence with member states and worked with them to identify ISIS-associated individuals to be sanctioned, oil produced in ISIS-held territory, and potential donations to ISIS via social media. Cooperating states have tried to shut down the accounts of sanctioned individuals and block their access to the international financial sector through cooperation with correspondent banks.

Depleting ISIS’ fighting force is also key. U.S. government estimates since the start of the Syrian civil war suggest that its force includes 40,000 foreign fighters from over 120 countries. Although the flow of these fighters into Iraq and Syria has slowed down substantially, the threat still poses a challenge to many countries, especially when the jihadists return to their countries of origin. Fortunately, there is a range of means to disrupt this process.

First, coalition partners can prevent radicalization and recruitment through Countering Violent Extremism (CVE) programs, which leverage community engagement and resilience and provide countermessaging and counseling to prevent potentially radical views from being acted upon. For instance, soon after the Syrian civil war commenced, the Belgian town of Vilvoorde was the top city in western Europe for ISIS fighters on a per capita basis, but after implementing community engagement and mentorship practices in 2014, the city has not seen a single community member choose to leave to join ISIS in Syria. The United States’ Global Engagement Center and the United Arab Emirates’ Sawab Center aim to counter ISIS’ propaganda online and assist local community members to do the same.

Coalition countries can also increase the arrest and prosecution of terrorist suspects as they cross borders. In September 2017, the UN Security Council issued guidance to member states for comprehensive counterterrorism laws and policies, leading over 40 countries from Bosnia to Malaysia to put new laws in place to make arrest and prosecution more likely.

In addition, many countries have increased the sharing of criminal information through agencies such as Interpol or Europol in order to screen suspect travelers who may be border-crossing foreign fighters. Interpol is now used by at least 60 countries to counter foreign fighters, a 400 percent increase in recent years. Law enforcement officials maintain that this will provide a significant interdiction effort against foreign fighters crossing borders to fight with groups such as ISIS.

PREVENTION IS KEY

Coalition and other actors should also reduce whatever socioeconomic appeal ISIS may hold in the region through providing much-needed humanitarian assistance. As Syria’s civil war enters its sixth year, more than 470,000 people have been killed. Almost seven million have been displaced, and of those, around five million are living as refugees outside the country. The UN has launched a stabilization fund to support civilians in areas ranging from water supplies to education to promote continuity of life and assist in humanitarian aid, exemplifying the importance of multilateralism in stability to mitigate the impact of terrorism.

At the core of ISIS’ strength is support from the local populations within the region. Undermining such support will require concessions to Sunni populations by both the Iraqi government and the regime of Syrian President Bashar al-Assad, such that local populations supporting ISIS and other extremists’ groups can find an alternative to them. As long as sectarian oppression in the region persists, the flames of any violent insurgency will continue to be fanned.

As long as sectarian oppression in the region persists, the flames of any violent insurgency will continue to be fanned.

A seminal RAND study from 2008 showed the top two reasons terrorist organizations end. Either their members choose nonviolent means to accomplish their objectives or local law enforcement neuters the group by arresting its top figures. In both cases, local politics play a key role, either by filling the political void left by the terrorist organization or by providing adequate support to local law enforcement. As the study’s authors note, it is unlikely that a terrorist organization will truly be defeated without the loss of popular support. ISIS’ influence in the region—and accompanying freedom to operate—largely grew out of then Iraqi Prime Minister Nouri al-Maliki’s sectarian favoritism and the resulting political backlash. Without a solution to those political problems, it is unlikely that local communities will rise up to help police arrest ISIS members or that potential ISIS recruits will choose nonviolence instead.

Without cooperation against ISIS, the group will gain strength. But countries need incentives to work together, to share information, to modify their laws, and to protect communities that are vulnerable to radicalization. One reason Iraq was removed from the list of countries for a proposed travel ban is that within the theater of war, even U.S. troops need significant local help, and a reduction in incentives to do so may make their efforts more difficult. Instead of overtures toward toughness and unilateralism, the international community’s core strength in truly defeating terrorist organizations lies in cooperation. The collective impact of joint efforts is the most potent in isolating and distinguishing the danger posed by terrorists, and the humanity shown in cooperation and openness is the best hope for removing the desire to become one.