Since the Syrian uprising began in March 2011, concerns over the country's chemical arsenal have largely reflected the fear that terrorists might steal them in the chaotic aftermath of Bashar al Assad's overthrow. Military use against the Free Syrian Army seemed less likely, largely because the use of unconventional weapons would violate international law and norms. If it broke that taboo, the regime would risk losing Russian and Chinese support, legitimizing foreign military intervention, and, ultimately, hastening its own end. As one Syrian official said, "We would not commit suicide."
But this week chemical anxieties shifted. President Barack Obama warned Syria that "[t]he use of chemical weapons is and would be totally unacceptable" -- a comment echoed by Secretary of State Hillary Clinton and Secretary of Defense Leon Panetta, both of whom said that use of the arsenal would cross a "red line" for the United States. Despite these admonitions -- and a barrage of reports that Syria is preparing to deploy its chemical arsenal -- it remains doubtful that Damascus is at the point where the use of chemical weapons against rebels makes tactical or strategic sense.
Chemical weapons have rarely been militarily decisive. In World War I -- which marked the historical debut of choking, blister, and blood agents -- they caused only 4 percent of the war's casualties and only 3 percent of those casualties died. Used episodically in the years since, blistering agents rarely achieved notable results. Italy had little success incorporating them into its attempted conquest of Abyssinia (Ethiopia), and Libya's use of blistering agents against Chadian forces in the 1980s had little impact on battle outcomes. Used in isolation, World War I-era chemical agents were relatively ineffective.
Other chemical agents, however -- most notably nerve agents, which kill by shutting down respiration and other vital functions -- have enabled some tactical successes, while killing tens of thousands civilians. The most notable is example is Iraq's use during its war with Iran, which reportedly suffered 60,000 casualties from chemical weapons. Although difficult to manufacture, nerve agents are immensely lethal and, in some cases, easier to weaponize and deliver. First developed by the Germans, these agents include tabun, soman, and sarin.
So, while blistering agents remain a likely element of the Syrian chemical arsenal, it is the regime's likely possession of nerve agent that provokes far greater concern. Experts note that Syria likely has hundreds of tons of sarin -- a lethal dose is approximately half a milligram. Deliverable by planes and artillery, 100-200 Syrian Scud missiles also reportedly serve as a quickly readied additional delivery platform. There is also suspicion that Syria possesses VX, a far deadlier nerve agent that is 100-400 times more toxic than sarin.
But even these weapons have become obsolete for states. They are rarely strategically decisive, they have been obviated by advanced conventional arms (and, of course, nuclear weapons), and they are stigmatized. That is why all but six states belong to the Chemical Weapons Convention, which bans the production and use of chemical weapons. Syria's weapons, produced beginning in the early 1970s with Egyptian assistance, have been intended to deter Israel's nuclear capability and to offset Syrian conventional inferiority. It's unlikely they could have served either purpose, but designed for use in large-scale, state-to-state warfare, Syria's chemical weapons are particularly unsuited for the urban fights that have characterized the civil war. Close-quarters combat renders chemical weapons not only ineffective but counterproductive; with sarin or VX, a simple wind shift could turn the deadly agent against the Syrian military. Syria's likely blister agent -- so called "mustard gas" -- is highly corrosive, remaining a hazard for forces attempting to occupy the affected area.