TSG IntelBrief: Strangling the Islamic State of Foreign Fighters
August 3, 2015

Strangling the Islamic State of Foreign Fighters


Bottom Line Up Front:

• A recent U.S. intelligence assessment showed little change in the overall number of fighters in the Islamic State, despite a year-long air campaign, though the group’s ability to move freely has been curtailed

• The estimated 10,000 fighters killed have been replaced with new fighters, many of whom are foreign fighters that crossed over from Turkey

• In this war of complicated dynamics, a relatively straightforward way to impact the conflict could be the effective and highly publicized closing of the Turkish/Syrian border

• The Islamic State cannot be bled to death but it can strangled; in part by denying the group fresh foreign fighters.


There are countless numbers and data sets that can be used to assess the multinational fight against the Islamic State: territory lost or gained; fighters killed or replaced; equipment seized or depleted; revenue raised or spent. All of these numbers are estimates, and all have huge variations in both actual numbers and in possible meaning. One of the most important numbers is also the hardest to determine: the number of fighters in the Islamic State.

A recently reported assessment by U.S. intelligence agencies found that, after a year of air strikes, the fighting strength of the Islamic State remains at the level of last year’s estimate: 20,000-30,000 fighters across Syria and Iraq. With reports that perhaps 10,000 Islamic State fighters have been killed in the last year, this assessment suggests that the group has been able to replenish its ranks at the same rate they are being depleted—a recipe for stalemate and slow attrition. While there is an argument that quality does not equal quantity, and that those lost were more proficient than their replacements, there is no argument that the group still has a large pool of potential members.

The group has been able to replenish its ranks primarily because it has anchored itself in the vulnerable communities of two war-torn countries, and leverages its strengths against the weakness of the Sunni communities over which it has control. This is a leverage that is most difficult to dismantle, as these conditions—endemic corruption, systemic persecution, and frenetic depredation—are what enabled the group to rise to its current level of localized lethality and global prominence. These conditions will not be resolved anytime soon.

A far more immediate impact on this immensely complicated battlefield can be made with the relatively straightforward—though not simple—decision to close the Turkish border with Syria. There likely is no other action that can as effectively decrease the ability of the Islamic State to replenish its ranks of motivated and murderous foreign fighters. Much more so than its rivals, such as Jabhat al-Nusra, the Islamic State in Syria depends on the accelerant that foreign fighters provide in terms of shocking violence and suicide attacks. Foreign fighters are also useful to the group in propaganda; they help perpetuate the perception of a caliphate. More than any terrorist group before it, the Islamic State depends on people traveling to it to both live and die, and to talk about both on the Internet.

Since, in this analysis, the Islamic State is as much a physical destination as it is an ideology, there is a case to be made that closing the border to foreign fighters would be the single most effective way to reduce the group’s capacity to regenerate. It is, of course, difficult for most countries to seal their borders. Yet Turkey does not have to close its entire border, but rather focus on the most probable foreign fighter routes. The eastern areas controlled by the Kurds are obviously poor crossing choices for would-be recruits of the Islamic State, as are the far western borders above Latikia, under the control of the Assad regime. The western-central areas on both sides of Aleppo need to be the focus of Turkish efforts.

Even if the border is not completely sealed, it should be made as difficult as possible for foreigners to cross in the target areas. And then, most importantly, this closure should be made as public as possible, with extensive coverage of security preparations, traveler delays, and foreign fighter arrests. The point is not just to physically deter people from crossing, but to psychologically prevent them from attempting the journey in the first place. So much has been made of the prowess of Islamic State recruiters; it is time to force them to work much harder, by having to explain away the near-impossibility of crossing into Syria. The appeal of living in a mythical caliphate needs to be countered with the real-world difficulties of getting there. The Islamic State is not going anywhere soon, given its relative strength and the deep-rooted problems that enabled its rise. Making it much harder for foreigners to physically get there, however, will be a significant achievement in what will be a long struggle.


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