We could speculate that the original plan two years ago was to quickly topple Assad's regime by supporting proxy forces, then secure and destroy his chemical deterrent. Obviously, that hasn't gone as planned. Now Israel and the US must be desperate to do something, anything, to secure the stockpile before Assad uses it to deter attack, or before it falls into the hands of rogue elements. A RAND report on Syria addressed the difficulties, the risks and the fact that the objective could not be reached without ground forces:
In spite of often casual rhetoric about “taking out” Syria’s chemical weapon capability, the practical options for doing so have serious limitations, and attempting it could actually make things worse. Locating all Syrian chemical weapon facilities (e.g., storage sites, production facilities) and defining them well enough to design effective conventional air strikes against them would require very precise and detailed intelligence. And depending on the weapons employed in the strikes and the exact nature of the chemical weapons to be destroyed, collateral damage from the attacks could be substantial. Prospects for eliminating Syria’s extensive chemical weapon capabilities through air attack do not appear promising. At the very least, accomplishing this objective would require ground forces, and even then it may not be possible to neutralize the regime’s entire arsenal. Air power could be used, however, for retaliatory threats or attacks to deter further chemical weapon use. Air power could also be used to target the regime’s most efficient ways of delivering chemical weapons, thereby decreasing the regime’s capacity to inflict mass casualties through their use. Above all, it is essential to note that each of these aerial intervention measures could lead to further, more-extensive U.S. military involvement in Syria, particularly if it did not achieve its initial strategic objectives. Also, it could trigger serious escalatory responses from other parties such as Russia. Therefore, anticipating and assessing potential next steps beyond an initial intervention effort should be central to any strategic planning for using air power in Syria.
An article in The Atlantic covered State Department veteran William Polk's assessment of the present Syria dilemma which is accompanied by a history of the use of chemical weapons and the international agreements covering them. His assessment of the situation also includes the important mention of the five-year drought and crop failure that preceded the Syrian civil war:
After the war, the British, strongly urged by Churchill, then Colonial Secretary, used combinations of mustard gas, chlorine and other gases against tribesmen in Iraq in the 1920s. As he said, “I am strongly in favour of using poisoned gas against uncivilised tribes.” In the same spirit, the Spaniards used gas against the Moroccan Rif Berbers in the late 1920s; the Italians used it against Ethiopians in the 1930s; and the Japanese used it against the Chinese in the 1940s… More recently in 1962, I was told by the then chief of the CIA's Middle Eastern covert action office, James Critichfield that the Egyptians had used lethal concentrations of tear gas in their campaign against royalist guerrillas in Yemen… Just revealed documents show that the Reagan administration knew of the Iraqi use in the Iraq-Iran war of the same poison gas (Sarin) as was used a few days ago in Syria and Tabun (also a nerve gas)… Finally, Israel is believed to have used poison gas in Lebanon and certainly used white phosphorus in Gaza in 2008... I cite this history not to justify the use of gas – I agree with Secretary Kerry that use of gas is a “moral obscenity” -- but to show that its use is by no means uncommon. It is stockpiled by most states in huge quantities and is constantly being produced in special factories almost everywhere despite having been legally banned since the Geneva Protocol of June 17, 1925… Use, production and storage of such weapons was again banned in the 1993 Chemical Weapons Convention (to which Syria is not a party). But nearly all the signatories to that convention reserved the right legally to use such weapons if the weapons had been used against them (i.e. no first strike). The Convention, unfortunately, contains no provision banning the use of weapons, as Saddam certainly did and as Assad is accused of doing, in civil war.
Brogan, Benedict. "Syria Asserts its Rights to Chemical Weapons." The Telegraph, January 7, 2004.
Fallows, James. “Your Labor Day Syria Reader, Part 2: William Polk.” The Atlantic, September 2, 2013.
"Footage of Chemical Attack in Syria is a Fraud." Russia Today, September 6, 2013.
Gold, Hadas. “N.Y. Times scraps AIPAC from Syria story.” Politico, September 3, 2013.
Air Power Options for Syria. Rand Corporation, Center for Middle East Public Policy, 2013.