Bernhard provides an excellent summary to the much longer article by Seymour Hersh carried in the London Review of Books. Hersh essentially provides an update on all the Empire's secret machinations of the their direct, and indirect support via Turkey, of the jihadist opposition forces in Syria. The crucial events were the bombing of the US embassy and CIA offices in Bengazi, Libya which brought a halt to direct weapons transfer to Turkey (the "rat line"), and the desperate act of Turkish authorities to instigate the false-flag operation of the gas attack supposedly launched by the Syrian government.
It is always interesting and a challenge to tease out the actual decision-makers in the US government. Notice that Hersh's unnamed, but trusted, sources frequently use the expression "the White House" in reference to decisions made, although occasionally the reference is to Obama. It is important to be aware that the White House is not only the residence of the president, but also contains the powerful National Security Council and the White House staff. Obama functions formally, and probably literally, as chairman of the NSC.
From my observations over many years, I have concluded that the president's main role, especially for the last few decades, is largely that of a public relations officer for the ruling class's government. It is unclear to me who functions as primary "deciders" within the National Security Council. Notice in one part of the article that the Chief of the White House Staff apparently made a very important decision independently:
In the months before the attacks began, a former senior Defense Department official told me, the DIA [Defense Intelligence Agency] was circulating a daily classified report known as SYRUP on all intelligence related to the Syrian conflict, including material on chemical weapons. But in the spring, distribution of the part of the report concerning chemical weapons was severely curtailed on the orders of Denis McDonough, the White House chief of staff. ‘Something was in there that triggered a shit fit by McDonough,’ the former Defense Department official said. ‘One day it was a huge deal, and then, after the March and April sarin attacks’ – he snapped his fingers – ‘it’s no longer there.’ The decision to restrict distribution was made as the joint chiefs ordered intensive contingency planning for a possible ground invasion of Syria whose primary objective would be the elimination of chemical weapons.And, behind the National Security Council and the While House staff functions the general foreign policy making center of the US, the Council on Foreign Relations.