The Saudi interests in the Syrian civil war is to push Iran's influence out of Syria, Lebanon and Iraq altogether. Saudi Iranian relations have been tense ever since Iran's Islamic revoultion in 1979. But the relations took a turn for the worse, with Iran's role in the US-Iraq war in 2003. By disassembling the Iraqi army and Saddam's Ba'ath party, the US created a power vacuum in Iraq which was quickly filled by pro-Iranian figures. And for the first time in a long time, a pro-Shiite state now bordered the Saudi Kingdom. This made the Saudis very anxious, because they too have a sizable Shiite communities, and they feel that this rise of Shiasm, could very well spread to their own country (especially in the oil rich gulf region). This is something Riyadh cannot tolerate. Since Iraq, the Saudis and Iranians have had several proxy clashes in Bahrain, Iraq, Lebanon and now in Syria.