The Wall Street Journal reported that "The U.S. has intercepted an order from Iran to militants in Iraq to attack the U.S. Embassy and other American interests in Baghdad in the event of a strike on Syria, officials said, amid an expanding array of reprisal threats across the region."
The date when our intelligence agencies intercepted the Iranian message on Iraq has not been publicly reported, but the Journal said that it was “intercepted in recent days.” So the timing fits: it seems probable that Obama became aware of the threats of retaliation that have been reported (and, perhaps, others that have not been made public) last week; most likely, late last week. Experts say that this is the reason why Obama suddenly changed his mind last Friday and decided to have Congress weigh in on the Syrian attack decision. It appears there was a possibility of major blowback, not just from an isolated terrorist or two but coordinated by Tehran itself.
In the event of a significant retaliatory response, Obama would not want to be out on a limb by himself on Syria.He would want it to be clear that the Syrian intervention was a decision for which the entire U.S. government was responsible, including some Republicans. This conclusion is even stronger given the risk that a significant retaliation traceable to Iran would escalate tensions and could lead to a broader and far more substantial conflict.
If the U.S. does bomb Syria and Iran does retaliate, this administration will suffer greatly for having discounted Iranian threats during the debate on whether to intervene in Syria.
There remains the question that some reports, not all from totally credible sources, indicate that it was not Assad who launched the chemical attack of Aug. 21 but opposition forces, possibly aided by the United States itself.