By Anthony D'Ambola Managing Editor 21 December 2018

This week, President Trump announced a complete withdrawal of ground troops from Syria. Amid the power vacuum stemming from the Syrian civil war, the Islamic State (ISIS) seized control of large stretches of the country – approximately 55 percent of its total area – and established a fledgling caliphate. In October 2016, after initially underestimating ISIS’ capabilities, the United States engaged militarily in Syria to drive the terrorist group from its strongholds. Two years later, ISIS has lost almost all of its occupied territory, with the exception of a small pocket of land on the Syria-Iraq border. None of this would have been accomplished without the help of Kurdish-led Syrian Democratic Forces (SDF), a ragtag group of Arab militias and the People’s Protection Unit (YPG), the military arm of the Kurdistan Workers’ Party (PKK). The SDF has been combating ISIS in Syria’s southeastern region while simultaneously carving out territory for itself in the country’s northeast region along Syria’s border with Turkey. The SDF has played an instrumental role in rolling back ISIS’ territorial gains in Syria. Without its presence, the United States would lack a reliable and capable ground ally in the region.

The reason – at least the publicly recognized one – that underpins the United States’ troop withdrawal is largely based on the idea that ISIS has been defeated. This notion is wildly misguided and has fueled an irresponsible decision. The Islamic State has lost control of almost all of its territory, but it remains a persistent threat to the region. It is acting as an insurgency and launching frequent attacks (an average of 75 per month in 2018) in Iraq while thousands of its fighters in Syria have gone underground; they are simply biding their time. Moreover, the group’s efforts towards social media recruitment and propaganda are still robust. The decision to remove troops from Syria is based, at least in part, on the idea that the Islamic State is a military force that functions only if it controls territory. This is a fundamental misunderstanding of ISIS, or of any modern terrorist group for that matter. The Islamic State, at its core, is an ideology and a crusade built upon a foundation of regional instability. As long as this instability and a lack of governance persists in Iraq and Syria, ISIS will remain a persistent and threatening force in the Middle East. As Brett McGurk, the State Department’s special envoy for Syria, stated in a press briefing last week, “the end of ISIS will be a …long-term initiative …nobody is declaring mission accomplished.”  

A ground forces withdrawal in Syria will have myriad negative consequences. Turkey’s president, Recep Tayyip Erdogan, considers the PKK, a Turkish political party that has long sought autonomy, a terrorist group. He has repeatedly expressed frustration with the Kurds’ receipt of support from the United States and recently vowed to launch a military assault against the Kurds in Syria. A troop withdrawal will give Erdogan the green light to do so. This will have reinforcing negative effects. Firstly, ISIS will certainly regroup in southeast Syria, as the YPG will be forced to combat the Turkish military in the northeast. Eventually, ISIS will likely retake some, if not most, of its previously held territory. We could end up back to where we started in October 2016. Compounding this potential reversal, the United States will no longer have a reliable partner to fight an ISIS resurgence, as the Kurds’ trust in the United States will be nonexistent. The YPG will likely be degraded to the point where they are unable to combat ISIS, and those able to fight will view the United States as an unreliable ally.

In addition to terrorism concerns, an escalation of Iran’s malign activities is another consequence of a U.S. pullback in Syria. Opportunities for Iran to broaden its influence in Syria and beyond will certainly arise if the United States does not sustain its military presence and support of the YPG, which will no longer able to oversee parts of the country. Iran’s strategic objectives in the region are particularly concerning. The Iranians will attempt to reestablish a land bridge through Syria to the Mediterranean, allowing them to reconstruct supply lines to Hezbollah in Lebanon. This will put additional pressure on Israel and increase its security risks. Iran will also enlist Hezbollah, which already maintains a notable footprint in Syria, to interdict even further in order to expand Iran’s influence in the country. Iran’s expansion in Syria will also have implications for Iraq, where Iran already retains outsize political influence. It utilizes Hezbollah to support numerous Shi’a militias, which have played a crucial role in sowing discord in the country.  To highlight the interconnected and reinforcing nature of destabilization, this discord will, in turn, increase incidents of terrorism. A lack of United States military presence will only serve to invite further encroachment from outside actors like Iran, as they will no longer be disincentivized from impeding on areas where the United States and the proxies it once supported wielded authority.

In January, the United States military proposed the creation of a 30,000-member Kurdish force (backed by American troops) to patrol northeastern Syria for at least the next two years. This is the correct course to follow. This plan will not move forward, however, without a U.S. military presence to act as a backstop against the Turkish military. President Trump has long advocated for a military withdrawal from Syria (and the Middle East as a whole) but, while some of his criticisms are valid, his solutions are short-sighted. He is repeating President Obama’s 2011 troop withdrawal from Iraq, a mistake that created a ripe landscape for ISIS to cultivate. Obama eventually had no choice but to re-deploy 4,500 troops – a fact President Trump should note. A complete ground forces withdrawal in Syria would abandon the Kurdish forces that have been so instrumental in combating the ISIS threat. The Islamic State will certainly take advantage of the resulting vacuum, and beating back the group a second time without an effective partner on the ground will eventually require re-engagement and an even more pronounced U.S. military footprint.

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Anthony D’Ambola is a Master’s Candidate in the Security Policy Program at the Elliott School of International Affairs at George Washington University. His research is focused on political instability and the intersection of terrorism and geopolitics.