Lawrence Korb, senior fellow at the Center for American Progress and former assistant defense secretary

At this point the details of what exactly happened outside Damascus this morning are still emerging. The preliminary evidence—based on amateur videos, photographs, and eyewitness testimony—indicates a large-scale attack using an unverified nerve agent that is likely not sarin. Unconfirmed reports indicate hundreds of civilian deaths in circumstances consistent with a chemical attack. The Obama administration has previously stated its belief that elements of the Assad regime have used chemical weapons on a small scale, but today’s attack—if verified—would represent a serious escalation in the use of these weapons. President Obama has also stated that, “a red line for us is [if] we start seeing a whole bunch of chemical weapons moving around or being utilized. That would change my calculus.”

The obvious question now surrounds how the United States and the international community should respond to deter the further use of these weapons, thereby preserving long-standing international consensus against the use of chemical weapons, without worsening the humanitarian situation in Syria and the wider region. For the United States, there is now also a vested interest in maintaining President Obama’s credibility in light of his publicly stated red line. 

But several key questions must be resolved before any steps are taken. First, reliable casualty counts must be established and the cause of death confirmed to be a nerve agent. Second, the United States must use its formidable eavesdropping and human intelligence tools to establish to the extent possible the chain of custody of the weapons used, and determine who issued the order and what unit or faction carried out the attack. There is an inclination to assume that the Assad regime is a coherent, unified body, but the regime is under tremendous pressure and there are numerous loyalist groups active in Syria today. Determining who made the call will be important in calibrating a proper response. Third, the United States should coordinate with its closest regional allies—Israel, Turkey, and Jordan—in advance to agree upon a response and present a unified position that secures our mutual interests.  

These steps will take time and will not satisfy the strident, emotional calls for an immediate and forceful response, but they are crucial to establishing the facts and ensuring legitimacy for international action. If it is established that the Assad regime orchestrated a chemical weapons attack on the scale reported, the United States will have to lead a much more aggressive campaign to deal with the long-term consequences of Assad’s actions. Under these circumstances, the administration must present its evidence of chemical weapons use to the United Nations and request the authorization of all necessary means to remove or apprehend those responsible. The United States should press the United Nations to designate the use of chemical weapons by the Assad regime against civilians as a crime against humanity, name Assad and his close supporters as war criminals, and refer the case to the International Criminal Court. 

If Russia continues to block meaningful action at the United Nations, the United States should consider limited cruise-missile strikes on those determined to be responsible. These strikes should not be undertaken if the targets are embedded in civilian areas. If it is determined that the use of chemical weapons represents an Assad regime policy, limited cruise-missile strikes should be undertaken against several militarily significant targets (e.g., airfields). The purpose of these strikes will not be to change the balance of power in Syria, which would require a much larger commitment and would likely dramatically worsen the humanitarian situation, but to present a clear cost to the Assad regime for any further use of chemical weapons and to maintain the credibility of President Obama’s threats.