Iran and the Saudis
The new Arab-Iranian cold war has been on for some time now. The Syrian crisis has only made it worse. Led by the Saudis, the Sunnis are determined to do what they can to check what they see as rising Iranian and Shia power. I'm sure the Saudis blame the Americans for the Shia government that now sits in Baghdad and for Bahrain, where Washington pressed for reform of in the early days of the Arab Spring, seemingly inattentive to Saudi concerns.
Iraq may be lost, but the game in Syria is still on and the stakes are high. Turning the Shia-affiliated Alawi regime into a Sunni one that can be influenced would be a tremendous victory for the Gulf Arabs. It would weaken the Iranians and break the exaggerated but still very real threat of Shia encirclement -- Iran, Syria, Lebanon, and Iraq. And that's why Riyadh is backing the rebels with money and arms and allowing individual Saudi clerics to sermonize about jihad and encourage non-Syrian foreign fighters to carry it out. This, of course has a potential downside. We saw the blowback in Afghanistan, where Saudi-inspired Wahhabi doctrine motivated a cadre of Arabs to fight first against the Russians and then against the West.
Tehran, on the other hand, is pushing back: propping up the Assads with concessionary oil, money, arms, and whatever the regime can contribute from its own large bag of repressive techniques. The Iranians may be out of touch on some issues, but it's hard to believe they don't sense that the bell is tolling for the Assads and for the four-decade-old strategic relationship with Syria. If and when Assad falls, Iran's window into Lebanon and the Arab-Israeli conflict is going to be much harder to keep open, particularly its key relationship with Hezbollah. But that doesn't mean Tehran is going to cooperate on keeping Syria quiet and stable. Indeed, the fear of Sunni encirclement will intensify, and Iran will want to meddle even more to keep the pot boiling (see: Iraq). Iran might even cling tighter to its nuclear program to enhance its leverage and own sense of security.
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