Syrian government soldiers captured by the Islamic State. The battles in Iraq and Syria are wars of annihilation where quarter is rarely given and where most prisoners of war are eventually killed. ISIS has also been vocal about genocidal intentions toward Shiite Muslims and Alawites.
The Islamic State (ISIS) caliphate is on the path to losing control of the core territory it dominates in both Iraq and Syria. What will then become of the thousands of foreign jihadists who joined ISIS, especially from Western countries? A major concern is that these fighters, or at least many of them, will return to their countries of origin where they will pose a major threat, especially in Europe.
There is also the risk that ISIS fighters, especially from other Middle Eastern or former Soviet states, will try to make their way to Europe as "refugees" rather than return to the police states from whence they originated. Reportedly only a small portion of ISIS fighters have become disillusioned with its ideology, and about half remain committed to it, rendering them impervious to counter-messaging and rehabilitation efforts.
The threat that foreign ISIS fighters pose may be significantly less than widely expected.
While this may finally be changing, Europe as a whole has had trouble with information-sharing on foreign fighters, and individual countries are unable to properly identify and track returning jihadists.
At first glance then, the situation looks dire. A closer look, however, indicates a more positive picture. The threat these foreign fighters pose may turn out to be smaller than widely expected, perhaps significantly less.
Understanding the reasons for this may help the authorities, especially in the West, plan properly to thwart those jihadists who do make their way back from the battlefields of the caliphate.
The Nature of the War
The battles in Iraq and Syria are wars of annihilation where quarter is rarely given and where, especially in Syria, most prisoners are eventually killed. ISIS has been particularly vocal about its genocidal intentions toward Shiite Muslims and Alawites, proudly advertising its war crimes, including the systematic slaughter of "sectarian" prisoners. For their part, the Iraqi security forces (composed largely of Shiite troops) and the largely Alawite Syrian army, not to mention the Shiite militias operating in both countries (notably Hezbollah) have committed their share of atrocities. Functionally speaking, these militias are often as enthusiastically murderous as ISIS members and have evidently also made it their practice not to take prisoners.
Moreover, the various government and government-aligned forces fighting ISIS are not the only enemies the organization has. Syria in particular is a multifaceted civil war with ISIS fighting numerous other anti-Assad factions, including nationalists and other jihadists. Since ISIS has brutally imposed its system on those conquered, there will be little love lost between the group and other factions, if and when it has to retreat. Popular and factional resentment of ISIS's vicious rule is thus likely to lead to revenge killings of its fighters once the opportunity presents itself. In particular, ISIS and al-Qaeda factions in Syria (notably Hay'at Tahrir ash-Sham) have spent extensive time and effort killing each other, and al-Qaeda is likely to view ISIS remnants—especially those who defected to it from al-Qaeda—as traitors who betrayed their oath of unconditional allegiance to al-Qaeda and its leadership.
For these reasons, it is reasonable to assume that large numbers of ISIS foreign fighters have already been killed. While figures vary widely, the loss rate of foreign fighters in Syria in particular has been appalling. For example, in September 2016, the Syrian Observatory for Human Rights reported that at least 52,000 of the more than 430,000 killed in the Syrian civil war were, by that point, foreign Sunni jihadists. Presumably, many of these were fighting for ISIS, which is one of the largest rebel factions. Certainly, more ISIS foreign fighters have been killed in Iraq. By all accounts, the present ground fighting, both in Mosul and in northern Syria, is intense, which means that ISIS is taking heavy casualties, which are likely to grow as the battle for Raqqa intensifies.
Furthermore, the Assad regime has a long history of treating any prisoners it takes with extreme brutality. Its opponents, including ISIS, may choose to go down fighting rather than be taken captive and endure such treatment. In addition, anybody who can be identified as a foreign fighter may be viewed by the Assad regime as "terrorists" who caused the war and may be meted even harsher treatment than other prisoners.
The Nature of ISIS
For ISIS fighters, dying while fighting is expected. So far, there have been few ISIS surrenders in the battle for Mosul where the organization has routinely used massed suicide bombers; and while it appears to prefer that its "martyrs" be volunteers, ISIS combatants can be ordered to undertake "martyrdom" operations. This means that such operations are accepted as a routine tactic and part of the self-identity of ISIS fighters; the group's recruiting campaign has made it clear that recruits should come prepared to die. Some ISIS jihadists have been executed for not fighting to the death while some have been executed for refusing orders to become suicide bombers. Even if some ISIS fighters are prepared to surrender, others are clearly not. Such diehards will fake surrenders and then try to kill their would-be captors. How many false surrenders will it take to convince any of those willing to take prisoners to shoot first and ask questions later?
Some ISIS jihadists have been executed for not fighting to the death.
ISIS has also announced its intention to execute anyone caught trying to desert; in Raqqa alone during some months in 2015, it executed 120 deserters. What this means is that ISIS has made it difficult for anyone to walk away from the fight.
ISIS also presents bureaucratic obstacles to those who may wish to flee the fight. It may well have confiscated foreign fighters' passports on arrival, or the fighter may have destroyed his passport to demonstrate he did not intend to return to his country of origin. If ISIS has someone's passport, the group is unlikely to return it. Further, in the confusion of a war, ISIS may inadvertently lose the passports. 
Foreign Fighter Recruits
While there are a variety of reasons that foreign fighters join ISIS, recruits are frequently drawn from what might be called the "murderously devout." These are a subset of the supporters of jihadism who believe that the ISIS interpretation of Islam provides the proper way to run a society. Often, Western recruits seeking a more authentic Muslim identity belong to this category and have joined the organization because they wanted to live in an imagined utopian Islamic society. They often believe they are engaged in a cosmic war of good against evil; some even believe they are fighting in the End of Times presaged in the Qur'an—"the Hour." People who have invested their identity in ISIS in this fashion are not likely to readily abandon the organization even when it is sustaining heavy losses.
ISIS recruits are frequently drawn from what might be called the "murderously devout." They may regard dying in battle as its own reward. As a result, a high attrition rate can be expected of foreign jihadists.
More importantly, having accepted the ISIS ideology and psychology, they may regard dying in battle as its own reward. An enemy who looks down the barrel of a rifle and sees paradise is not likely to surrender. Therefore, a high attrition rate can be expected of foreign jihadists. Additionally, the limited fighting experience of most Western foreign fighters is likely to encourage ISIS commanders to view them ultimately as expendable. In the first place, most Western jihadists have not had prior military training or experience. ISIS has tended to use them in support roles, including its extensive media operations. However, as the ISIS territory further contracts, this "B" list is likely to be pressed into the front line. While the organization provides several weeks' training for new recruits, this is unlikely to give them more than very basic combat skills. This means they are likely to take heavy losses once in combat. Additionally, inexperience may lead them to overrate their capabilities, leading them to take risks that better-trained or more experienced troops would not.
Moreover, Western foreign fighters are often not trusted—they are reportedly closely watched. Many are said to be in jail because they wanted to desert. Even if ISIS does not execute them on such suspicions, the group may opt to deal with potentially unreliable jihadists as the Soviets used their "punishment battalions" in World War II: Push them into combat, preferably in the first wave, to clear land mines and barbed wire, so to speak, with reliable troops coming up behind who will either shoot them if they try to surrender or retreat, or take advantage of their deaths to clear the way. In either case, such fighters are likely to incur heavy losses.
Concern over an influx of returning foreign jihadists may also be mitigated to some degree by a reduced flow of foreign fighters to the region. This has occurred for at least two reasons:
- In the past, a significant portion of recruits was drawn to the image of ISIS as a victorious, all-conquering army sweeping its enemies before it. Those days are long over and ISIS is now fighting and losing a defensive war.
- Because of improved border control by surrounding states, especially Turkey, ISIS has largely lost physical access to the outside world and its potential pool of foreign jihadists. While in the past, Ankara was a comparatively open environment for ISIS, this has changed as the terror group has increasingly targeted Turkey. Further, most of the Syrian side of the Turkish-Syrian border is now controlled by the Kurds, who number some of ISIS's most determined opponents.
Augmenting the West's Defenses
EUROPOL researchers claimed in mid-2016 to have information on more than four thousand Europeans who had traveled to join ISIS and its associates.
Not only is the size of the potential pool of returning jihadists likely smaller than feared, but there are other steps that can reduce the danger they pose. For a start, depending on where they come from, foreign jihadists may be very reluctant to return to their countries of origin even if they can do so. This is likely to be the case if they come from states with governments that take a very hard line against would-be jihadists, such as Russia and the United States. Imprisoning them for having been foreign fighters helps deter them from returning.
A systematic effort to keep Western jihadists from coming back must consist of at least two parts:
First, it involves a comprehensive attempt to identify foreign fighters. Unfortunately, such efforts did not start until recently; until at least mid-2015, international undertakings to identify Westerners going to join ISIS in the Middle East were very fragmented. Now, however, there are a variety of efforts underway to identify such Western jihadists. These include those of EUROPOL, which in mid-2016, claimed to have information on more than four thousand Europeans who had traveled to join ISIS and its associates. INTERPOL as well as the Counterterrorism Group of the Club de Berne are also working to identify Western jihadists, and the Schengen Information System, a large-scale data system that supports external border control and law enforcement cooperation in EU states, had data on eight thousand terror suspects by early 2017. In addition, there are private efforts such as those of the London-based International Centre for Study of Radicalization and Political Violence or the database of Samia Maktouf on Francophone jihadists.
Furthermore, much information on foreign jihadists has been recovered from the Middle East itself, including up to 3,800 profiles provided by a defector, along with a large collection of apparently credible information acquired in Turkey, and extensive information gathered after the capture of the town of Manbij in Syria. For their part, Western security and law enforcement agencies are finally making efforts to consolidate and expand this data, pooling the results in order to identify comprehensively those who have gone abroad and their current status. These databases should be kept as minimally classified as possible to enable maximum sharing with allies, including those in the Middle East, as Washington has apparently been doing with Operation Gallant Phoenix in Jordan.
Second, affected states need to start a systematic effort to apprehend and prosecute foreign jihadists. This consists of several components:
- Mounting a vigorous effort to apprehend foreign jihadists before they return: British and other European intelligence services are apparently cooperating with rebel groups to find, capture, and return imprisoned ISIS supporters.
- Turning ISIS's confiscation of foreign fighters' passports to an advantage: Anyone who shows up at an embassy in a surrounding country and reports his or her passport lost or stolen should face very close scrutiny.
- Reversing current Western counterterrorism efforts: Rather than prevent people from going to the Middle East to join ISIS or other terrorist groups (where the attrition rate is much higher), keep them from returning. A better policy would be to let them go and concentrate efforts on keeping out those who attempt to return from the battlefield. To accomplish this, all Western governments should suspend, and preferably revoke, the passport of anyone who is confirmed as having gone to join ISIS or any other terrorist organization. The intention is to block their return and disrupt their ability to travel to other places.
ISIS terrorist Khaled Sharrouf became the first Australian to be stripped of citizenship under anti- terrorism laws. These provide legal procedures for revoking the citizenship of any dual or naturalized citizens documented as having gone abroad to fight for terror organizations.
The Western nations would do well to follow Australia's precedent and develop legal procedures for revoking the citizenship of any dual or naturalized citizens documented as having gone abroad to fight for terror organizations. Any jihadists wishing to return home will need to earn the right to do so. They should be allowed to come back only if, functionally speaking, they defect, i.e., they agree to unconditional cooperation with security authorities. If they refuse, they should be prosecuted not just for providing material support to terrorism, but for treason, by committing the equivalent of joining a hostile military in wartime. According to U.S. law, an American convicted of treason or who joins the military of a hostile state loses his or her U.S. citizenship. Washington has begun proceedings to do so in at least one case, that of Iyman Faris.
Western authorities should also be highly skeptical of claims of success in efforts to rehabilitate jihadists. As with gang members, such programs may work on some of those on the fringe of these organizations, but for the hard core whose identity is rooted in jihadism—and this should be the default assumption for anyone willing to travel to the Middle East to join the jihadists—these programs are probably a waste of time and money. ISIS recruits willingly joined an openly murderous organization, and they joined it because they agreed with it. The group has never hidden what it was doing or why it was doing it, so recruits cannot claim they joined out of ignorance or did so in spite of what ISIS is. Washington should view these people in the same light as those who might join the Mafia, the Ku Klux Klan, or, even more appropriately, people who might have moved to Nazi Germany to join the SS. In addition, hard-core returnees may refuse to even participate in such programs.
The above discussion does not mean that there will be no threat. ISIS is working diligently to establish a network for continuing terrorist operations in the West, and it is not the only group that foreign jihadists have joined—al-Qaeda in particular remains active. Further, returning fighters are not the only potential source of recruits for terrorist operations. Radicalized migrants and refugees, radicalized native-born Muslims, alienated non-Muslims drawn to jihadist ideology, and the criminal underclass all pose real danger. Hence, while the danger to the West from returning ISIS jihadists may be less than widely expected, the threats from these returnees and other sources remain real.
Thomas R. McCabe is a retired Defense Department analyst and a retired U.S. Air Force reserve lieutenant colonel who worked ten years as a Middle East military analyst and two years as a counterterrorism analyst. This article represents his work and should not be considered the opinion of any agency of the U.S. government.
 An estimated 271 jihadists had returned to France by August 2017. Newsweek, Aug. 6, 2017. See also: Deutsche Welle (Bonn), July 26, 2016; The New York Times, Sept. 17, 2016; The Washington Post, Oct. 24, 2016.
 The Washington Post, Nov. 29, 2016.
 The Guardian (London), May 13, 2017.
 Newsweek, Dec. 22, 2016.
 "The Rafidah: From Ibn Saba to the Dajjal," Dabiq, al-Hayat Media Center, Jan. 2016, p. 45.
 The Washington Post, Nov. 20, 2016; Jack Watling, "The Shia Militias of Iraq," The Atlantic, Dec. 22, 2016.
 The Guardian, Aug. 24, 2014; Aki Peritz, "Self-Defeating Brutality: Why a war without mercy against ISIS is destined to fail," Slate (New York and Washington, D.C.), May 4, 2015.
 Charles Lister, "Al-Qa'ida Plays a Long Game in Syria," Combating Terrorism Center, West Point, Sept. 11, 2015;Charles R. Lister, The Syrian Jihad (New York: Oxford University Press, 2015), p. 104.
 The Hill (Washington, D.C.), Dec. 17, 2016.
 "About 430 thousands were killed since the beginning of the Syrian revolution," Syrian Observatory for Human Rights, Coventry, U.K., Sept. 13, 2016.
 "Out of Sight, Out of Mind: Deaths in Detention in the Syrian Arab Republic," United Nations Human Rights Council, (A/HRC/31/CRP.1), Feb. 3, 2016; see, also, Ben Taub, "The Assad Files: Capturing the top-secret documents that tie the Syrian regime to mass torture and killings," The New Yorker, Apr. 18, 2016; Adam Ciralsky, "Special Report: Documenting Evil: Inside Assad's Hospitals of Horror," Vanity Fair, June 11, 2015.
 Lister, The Syrian Jihad, chap. 4.
 Mark Perry, "How Iraq's Army Could Defeat ISIS in Mosul—But Lose Control of the Country," Politico (Arlington, Va.), Dec. 15, 2016; Long War Journal (Washington, D.C.), Dec. 6, 2016; Radio Free Europe/Radio Liberty, May 21, 2014; Defense One (Washington, D.C.), Sept. 12, 2014.
 Fox News, Jan. 12, 2016; Peter Van Buren, "Islamic State's rules of attraction, and why U.S. countermoves are doomed," Reuters, Oct. 21, 2014; "ISIS 'Biter' Squad Vanishes When Called for Suicide Bomb Duty," Clarion Project, Washington, D.C., Nov. 15, 2016.
 Reuters, Nov. 29, 2016.
 Daily Beast (New York), Nov. 14, 2016.
 Newsweek, Oct. 15, 2016; Sami Moubayed, Under the Black Flag (New York and London: I.B. Tauris, 2015), p. 135.
 "The Isis papers: a masterplan for consolidating power," The Guardian, Dec. 7, 2015.
 Sunday Express (London), Oct. 19, 2014; NBC News, Sept. 3, 2014; The New York Times, Mar. 21, 2015; Benedetta Argentieri, "'Lady Jihad' Lured Her Family into Terror; Fatima Az Zahra convinced her parents and sister to move to Syria... it didn't go well," War Is Boring, July 9, 2015.
 "By the numbers: ISIS Cases in the United States," Center on National Security at Fordham Law, New York, Mar. 1, 2014-June 22, 2015; Cori E. Dauber, "ISIS and the Family Man," Small Wars Journal, July 1, 2015; Sydney [Aus.] Morning Herald, July 9, 2015.
 Rick Noack, "The ISIS apocalypse has been postponed but the militants might still believe in it," The Washington Post, Oct. 17, 2016.
 Moubayed, Under the Black Flag, p. 156.
 Mike Giglio and Munzer al-Awad, "How to Lose Your Mind to ISIS and Then Fight to Get It Back," Buzzfeed, Apr. 13, 2016.
 Aaron Stein, "The Islamic State in Turkey: A Deep Dive into a Dark Place," War on the Rocks, Apr. 6, 2016; Meira Svirsky, "Secrets and Lies: Turkey's Covert Relationship with ISIS," The Clarion Project, Washington, D.C., Mar. 29, 2016; Uzay Bulut, "Turkey Releases ISIS Suspects," The Clarion Project, Apr. 3, 2016.
 "Combating Terrorist and Foreign Fighter Travel," U.S. House of Representatives Homeland Security Committee Task Force, Washington, D.C., Sept. 2015, pp. 28-30.
 BBC News, Aug. 2, 2015; Daily Mail (London), May 28, 2016; Reuters, Aug. 8, 2016; The Guardian, May 13, 2017.
 Mary Anne Weaver, "Her Majesty's Jihadists," The New York Times, Apr. 14, 2015; Mitch Prothero, "Why Europe Can't Find the Jihadis in Its Midst," Buzzfeed News, Aug. 21, 2016.
 Der Spiegel Online (Hamburg), July 18, 2016; Reuters, July 27, 2016; Defense One, Oct. 6, 2016.
 The Times of Israel (Jerusalem), June 22, 2017.
 The New York Times, July 27, 2016.
 BBC News, Oct. 12, 2016.
 Aki Peritz, "A Jihadi Bride Has Second Thoughts. Should Britain Let Her Return?" Overt Action (Chicago), Aug. 20, 2015; The New York Times, Aug. 29, 2016.
 "U.S. Code, Title 8, Chapter 12, Subchapter III, Part III, § 1481," Cornell University Law School Legal Information Institute, Ithaca, N.Y.
 Fox News, Feb. 11, 2017; Kavitha Surana, "Justice Department Moves to Revoke U.S. Citizenship from Man Convicted in 2003 Terror Plot," Foreign Policy, Mar. 21, 2017.
 Leslie Shaw, "French Deradicalization Plan: So Far, Not Working," The Clarion Project, Washington, D.C., Sept. 18, 2016.
 Clarion News, The Clarion Project, Washington, D.C., Nov. 3, 2016.
 Daveed Gartenstein-Ross and Nathaniel Barr, "[Hot Issue] Recent Attacks Illuminate the Islamic State's Europe Attack Network," Jamestown Foundation Hot Issue, Apr. 27, 2016.
 On the criminal underclass, see, for example, The Daily Beast, Feb. 10, 2017.