"They can do what they want there frankly," commented President Trump in a recent Cabinet meeting regarding Iran's role in Syria. Unsurprisingly, Trumps' remarks attracted a flurry of outrage. "Worst counter-Iran strategy ever," tweeted Jonathan Schanzer of the Foundation for Defense of Democracies. In a similar vein, Shalom Lipner, a non-resident senior fellow at the Brookings Institution, accused Trump of "conceding the region to Iran and its friends."
In fact, Trump is essentially correct while his critics have it wrong. Regardless of whether one agrees with Trump's exact words, Trump is right in his broader analysis that the U.S. mission in Syria as it stands (and which many of his critics seem to want to extend indefinitely) is not a meaningful counter to Iran in Syria.
For example, it is frequently claimed that the U.S. presence in northeastern Syria and in Tanf (a desert area in southeast Syria on the border with Iraq) blocks an "Iranian land route" stretching from Iran to Lebanon. Strictly speaking, an "Iranian land route" already exists via the town of Albukamal on the banks of the Euphrates River and nearby desert areas to the south on the border with Iraq, as these areas are currently controlled by the Syrian government and its allies.
Indeed, Iran's Islamic Revolutionary Guard Corps (IRGC) maintains a strong presence in Albukamal. The IRGC has set up a local affiliate in the town led by an individual who goes by the name of Shakir. In addition, via its "Friends' Security Office," the IRGC coordinates with the Syrian military and security command in the area for the return of locals to their homes. There is also some evidence to suggest that conversions to Shi'i Islam are taking place in Albukamal. All these points illustrate an IRGC interest in maintaining a "land bridge" between Syria and Iraq, and the American presence on the other side of the Euphrates does not prevent that or the possibility of Iranian smuggling of weapons through the more remote desert border areas immediately to the south.
In any event, the obsession with the "land route" concept is a case-in-point of missing the bigger picture. While there is an IRGC interest in the idea, it is a long-term project and remains secondary to the maintenance of its reliable air route, which has allowed Iran to bring in weapon shipments, personnel, and allied militiamen throughout the war. The U.S. presence in Syria has done nothing to disrupt that air-route.
Similarly, much of the "counter-Iran" discourse has overlooked Iran's consolidation of its presence in western Syria, where Iran's aim of integrating itself into the system of Assad-led Syria is much more apparent. The foremost sign of this integration exists in a project called the Local Defense Forces (LDF), which should not be confused with the more familiar National Defense Forces. The LDF project illustrates the absurdity of calls to maintain a U.S. presence in Syria until Iranian forces/"Iranian-commanded"/"Iranian-backed" forces (pick your formulation) withdraw from Syria.
The LDF is in essence a joint project between the IRGC, the IRGC's key Lebanese ally Hezbollah, and the Syrian military. A variety of units can be found in the LDF, and they do not all have the same profile. Some units, for example, have a direct affiliation with Hezbollah. Others are directly commanded by Syrian army officers but receive logistical support and/or training assistance from the Iranians. One unit — Saraya al-Areen (an Alawite group from Latakia) — displays an intriguing case of dual affiliation. Part of Saraya al-Areen is affiliated with the LDF, and part of it is affiliated with the Syrian military intelligence.
One LDF project of particular interest is the "Aleppo Defenders Legion": set up following the Syrian government's recapture of Aleppo city in its entirety, the project demonstrates an Iranian interest in reconstruction and civil society in Aleppo city. Headed at the top level by an Iranian (al-Hajj Mohsen), the "Aleppo Defenders Legion" also has Syrian military personnel in its lower command structures.
A variety of decrees on the LDF were passed with the approval of Syrian president Bashar al-Assad in April 2017. Among other terms, the decrees stipulate that the relationship of LDF units with the Iranians will remain "until the end of the crisis in the Syrian Arab Republic" or another decision is issued. In this case, the meaning is that the relationship will endure so long as the civil war continues and the Syrian government has not reasserted itself over the entirety of Syrian territory (unless Assad decides to issue a new decree). An indefinite U.S. presence serves as a justification for that relationship to remain and become further entrenched.
In reality, the only way the U.S. presence in Syria can meaningfully "counter Iran" is if the U.S. decides to engage in extensive offensive action against the Syrian government and its allies. In other words, waging a war for control of Syria. Besides the fact that there is no political willpower for such an initiative, the notion of expanding the U.S. mission in Syria beyond its counter-Islamic State purpose in this way is of extremely dubious legality.
Trump's critics, however, prefer to overlook these points rather than acknowledge what "countering Iran" in Syria would actually look like. Indeed, some justifications for how the U.S. presence supposedly counters Iran border on the ridiculous, such as the notion that the presence prevents Iran from seizing Syrian oil fields that could supposedly boost Iran's economy.
There are legitimate reasons to be concerned about an abrupt U.S. withdrawal from Syria, but the "counter-Iran" angle is not one of them. Instead, policy should be focused on trying to guarantee the standing of the U.S.-backed Syrian Democratic Forces (SDF) in its regional environment, such as through a deal with the Damascus government or a détente with Turkey, which controls the SDF's entire northern border and main access to the outside world. That way, an attack on the SDF by its rivals can be averted, preventing the rise of a vacuum that the Islamic State's remnants could exploit.