A chemical weapons attack allegedly carried out by Syrian government forces against the rebel‐​controlled city of Douma has prompted the Trump administration to consider military strikes against the Assad regime. The United States will likely follow through with military retaliation given last year’s U.S. missile strike against a Syrian air base following a similarly large chemical weapons attack. Since the last U.S. attack clearly failed to deter Syria from using chemical weapons, the Trump administration faces pressure to inflict greater pain on the Assad regime this time around. However, a stronger U.S. military response—or any military action for that matter—carries more risks than rewards.


The argument supporting U.S. military action is more or less the same as the argument made in 2017: the United States must punish the Assad regime in order to deter any future use of chemical weapons by the regime. However, Washington seriously overestimates its ability to influence or change Damascus’s behavior.


In theory, deterring the future use of chemical weapons requires the United States to make the costs of using these weapons unacceptably high. Over the course of the civil war, the Syrian government has repeatedly demonstrated the ability to absorb a great deal of military and economic costs. A military strike against Syrian air bases or chemical weapon sites may cause some temporary slowdown in the regime’s operations but it will neither end the civil war nor prevent the regime from using chemical weapons in the future. Moreover, Russian and, to a lesser extent, Iranian support for the Syrian government will help insulate Syria from the costs of U.S. military action.


Using military force to prevent future chemical weapons attacks would require much more than a limited attack. Short of deposing Assad, which Russia and Iran would try hard to prevent, the United States would have to carry out sustained attacks against air bases, command and control assets, and chemical weapons sites to degrade the regime’s ability to conduct future chemical weapons attacks. This would be a major escalation of the U.S. military role in Syria, which is at odds with President Trump’s desire to reduce America’s involvement in the country. There is also no guarantee that Assad and his allies would be cowed by a U.S. escalation. If Syria responds with more chemical weapons attacks or some other form of counter‐​escalation the United States would have to decide to up the ante or back down.


Another risk of a larger U.S. military response is the increased likelihood of inadvertent escalation with Russia. A sustained U.S. military pressure campaign that lasts long enough to significantly degrades the Assad regime’s chemical weapon capabilities would necessarily increase the probability of American and Russian forces making contact with one another.


Figuring out what limited military attack can deter Assad from using chemical weapons without risking a broader escalation of the U.S. role in Syria—what my colleague John Glaser called the “Goldilocks military option”—is a practically impossible needle for the Trump administration to thread. A strike that minimizes escalation risks will be too small to change Assad’s calculus about chemical weapons and a larger attack risks escalating a conflict that the United States has no great interest in fighting. The Trump administration must come to terms with the limitations of U.S. military power.