Seymour Hersh writes that Obama decided not to attack Assad in Syria because he found out that the gas attack was committed by the Islamists of al-Nusra. Before that, he was planning a massive attack.

Hersh's sources say that Turkey supported al-Nusra in making sarin. They also say that the CIA was sending US weapons to jihadists in Syria through Turkey, but in 2013 Obama decided to stop it, and that Erdogan ordered the attack so as to bring the US into the war against Assad.

I still think it is important to find out who started the rebellion in Syria. Was that set up by Turkey and Saudi Arabia and the US?