U.S. intelligence has detected increased activity at Syrian chemical warfare facilities, raising concerns about the regime potentially using chemical weapons (CW) against the opposition. Although such an action would likely only be carried out in extremis, Bashar al-Assad and his cohorts are approaching that very status. Given the regime's lack of regard for the casualties it has already inflicted and the value it places on its own survival above all else, the United States must prepare for the growing possibility of CW use in Syria.
After twenty months of internal war, the regime is in an increasingly difficult military situation. It suffered substantial reverses in November, losing territory, positions, troops, and equipment, including combat aircraft. The fighting capacity of its forces appears to be diminishing, and its standard tactic of bombing and shelling opposition areas, primarily civilian, is becoming less effective and more costly due to rebel antiaircraft fire and other tactics. As a result, pressure is undoubtedly rising within the regime to take different and more effective action -- that has been the pattern for Damascus since the emergence of armed opposition in summer 2011.
THE REGIME'S CHEMICAL ARSENAL
Syria has a formidable CW capability. Its large inventory reportedly includes the nerve agents sarin and possibly VX, as well as mustard gas, a blister agent. Means of delivery include aerial bombs, missiles (e.g., Scuds), and artillery shells and rockets.
The Syrian military is trained to use these weapons and has the doctrine, forces, and munitions to carry out such attacks. These forces can reach anywhere in the country, and there is very little the opposition Free Syrian Army could do to stop them. Without intelligence warnings from external sources, rebel combatants and civilians would be highly vulnerable to surprise chemical attacks, increasing the chances for major casualties.
The regime could use chemical weapons in a variety of ways, from a limited or demonstration attack to large-scale offensive or defensive use to fundamentally change the military situation. At present, reports that the regime is weaponizing relatively small quantities of agent suggest the former. Limited CW use could be controlled better in terms of effects and visibility. The regime might also find it easier to explain away small-scale strikes as the work of "terrorists" or as a justifiable response to the military situation and the threat to the country.
One form of limited attack could be a strike against a specific military target, aimed at affecting a local but important tactical situation. Such an attack would also demonstrate that the regime was ready, willing, and able to carry out such actions.
The regime could also conduct small-scale strikes on civilian targets to intimidate the population or punish them for supporting the rebels. This would be an escalation from the regime's routine use of explosives and incendiary weapons against civilians and could produce substantially greater casualties. It would undoubtedly have profound psychological effects on an essentially defenseless population.
As for broader CW use, the regime could employ such weapons to support ground offensives in key areas where its forces have been unable to achieve success via conventional tactics (e.g., around Maarrat al-Numan in Idlib province; in and around Aleppo city; in Deir al-Zour province, perhaps near Abu Kamal or Mayadin). It could use them to support defensive operations in places where rebel forces are on the offensive (e.g., the relatively remote Raqqa province) or have regime forces surrounded (as happened at the 46th Regiment base near Atareb in Aleppo province and the artillery fire base at Mayadin; in both cases, the positions fell to the rebels after prolonged siege and final assault). Using CW in close proximity to its own forces would be risky, but the military has some chemical defense equipment and training and might be able to provide a measure of protection.