The regime could also use persistent CW agents for area denial, striking lines of communication, shelters, and medical and food facilities to prevent rebels and civilians from using them. Finally, local military commanders operating independently of the government could decide to use CW on their own, whether out of revenge, frustration, fear, or other motivations. This would of course depend on access to munitions and delivery means, but in conditions where units are isolated or the chain of command is breaking down, such use is possible.
Unfortunately, the international community's track record so far may have given Assad a bad lesson regarding the potential consequences of CW use. The regime's massive escalation of violence throughout the war -- including use of field artillery against civilians, aerial bombing of population centers, and routine use of cluster munitions -- has gone largely unpunished, and Damascus has likely concluded that raising the stakes even higher would carry few real repercussions. It may therefore believe it can get away with limited CW use.
In theory, various political constraints could deter the regime from such a course. These include a likely irreparable break with the country's entire Sunni population, a probable rupture in relations with China and Russia, and great embarrassment for its allies Iran and Hizballah. More important, CW use would probably mobilize the West and Sunni Arab states to directly intervene in the conflict, sealing the regime's fate. Additionally, all those involved in ordering and carrying out CW attacks would risk international judicial action -- a prospect that could spur some regime members to mount a coup. Finally, the regime would have to deal with the massive public relations disaster that CW use would bring.
There are also military constraints. Chemical weapons are not just another device that can be pulled from storage and fired -- regime forces must also consider accuracy and reliability issues, meteorological factors (wind, humidity, temperature), agent choices (persistent vs. nonpersistent), and consequence-management issues (treatment of casualties, force protection, decontamination).
IMPACT OF CW USE
If the regime does decide to use chemical weapons, it could have significant effects on the military situation. The rebels have no protection against CW and no training to deal with such weapons; they barely even have experience with the effects of riot-control agents and smoke. They would be highly vulnerable, and the regime could achieve tactical or broader gains.
Politically, CW use could weaken the opposition, undermining the all-important link between the civilian population and the armed rebels. The significance of this deterioration would depend on the resilience of the population, which so far has proven steadfast in the face of all regime attacks.
There would also be humanitarian consequences, including probable refugee flows out of affected areas, the need to treat casualties, and decontamination requirements. The ability of NGOs and humanitarian groups to continue operations in such conditions would be tested.
Yesterday, President Obama reiterated that the United States would not accept the use of chemical weapons by the Syrian regime, and that there would be consequences for such use. Although Washington issued similar warnings in the past, the situation has changed, and the administration must be prepared to have its declaration tested. CW use is by no means a given, but the potential has gone up substantially and will grow as the regime's fall comes closer.
Upholding the U.S. declaration requires readiness to commit armed forces to eliminating Syria's CW capability and punishing the regime and its forces for using them. It means having military assets earmarked or in place to act quickly with overwhelming force, and to deal with the post-attack environment. It does not mean relying on diplomacy as the sole or even main response. Failure to respond with force to any use of chemical weapons would be dire. The regime would see it as a signal to conduct more attacks, and the opposition would see it as a complete abandonment.