While it has become increasingly unfashionable to argue the realist perspective on U.S. foreign policy in the Middle East, that perspective does provide an instructive framework for understanding the Obama administration's new policy of limited military intervention in the Syrian Civil War.
In order to view that new policy from a realist standpoint, we first have to sideline the "moral" reason offered by the Obama administration to justify its new policy, i.e. the notion that Assad and his government crossed a "red line" by using chemical weapons to kill at least 150 people. Never mind that U.S. intervention was not prompted earlier, when over 90,000 deaths were inflicted by conventional weaponry. Throughout history, great powers have had to rally domestic popular opinion in support of otherwise unpopular military actions. From the Gulf of Tonkin to Saddam's weapons of mass destruction to Assad's use of chemical weapons (to cite just the obvious examples that come to mind), no major power in recent times has been more effective at employing a diversionary moral rationale for its realpolitik than has the U.S.
So, what is the basis of the realist view? First, over 80% of the world's Muslims are Sunnis. With the exception of Iran, Iraq, Lebanon, and Syria, virtually all Muslim governments are Sunni-controlled. These non-extremist, Sunni governments, from Egypt, Turkey, Jordan, Saudi Arabia, the Gulf States, and from one side of North Africa to the other, all support the Sunni rebels in Syria. Any effort by the U.S. to tilt the balance of power in favor of the Syrian rebels strengthens the U.S.'s position with these Sunni governments.
The realist perspective also assumes that the U.S. will always have to be vigilant against Islamic terrorists, but that this would be true regardless of what happens in Syria. Even if, in the worst case, the Syrian rebellion were to morph into a jihadi-influenced Islamist regime, that regime would have its hands full dealing with a persistent Alawite (Shia-allied) rebellion within its own borders, as well as a Hezbollah-dominated Lebanon and a Shiite dominated Iraq surrounding Syria. For a jihadist-Islamic regime in Syria, hatching terrorist plots against the U.S. would not be a high priority, to say the least.
Given the view of every U.S. government since at least 1967 that Israel's security is vital to America's national interest, the realist perspective on U.S. intervention in Syria will, of course, incorporate the Israeli perspective as well. While there is as little love lost between Israel and a Hamas that supports the Syrian rebels as there is between Israel and a Hezbollah that supports Assad, the consequential difference is that Israel knows it can easily contain Hamas. The fact of the matter is that Hamas is relatively weak and increasingly isolated. Public rhetoric aside, neither Sunnis nor Shiites care much about Gaza, with Hamas in particular being viewed as an irritant by virtually all parties invoved in the Syrian conflict (including even Hamas's supposed mentor, the Egyptian Muslim Brotherhood).
The Israeli perspective on the strengthening Iran-Hezbollah-Syria axis, on the other hand, is very clear: it represents the most powerful military threat that Israel has faced in the post-1967 era. Anything that weakens that alliance helps Israel's security position in the region. Other than the Golan Heights border, which Israel can easily and ably defend, there is no contiguous geographic pipeline that Sunni Islamists and jihadists can readily use to support militant Palestinians, much less Hamas specifically. Jordan, the only Sunni governed country between Syria and Israel (other than the short and well defended Syrian-Israeli Golan Heights border itself) is the most U.S. and Israel friendly country in the entire Middle East. It is a far cry from the Syria-Hezbollah (Lebanon) border pipeline that Israel has to contend with currently.
In terms of the nuclear weapons development standoff between the U.S. and Iran, any successful effort to minimize Iran's footprint in the Middle East is central to the realist perspective on U.S. foreign policy. A new Syrian government controlled by Sunnis, even one with a strong jihadist influence, would sharply curtail Iran's influence in both Syria and Lebanon, and thereby strengthen Israel's security as well as that of America's regional Sunni allies accordingly.
In the final analysis, the realist perspective on the U.S.’s latest policy shift favoring limited military intervention in Syria is this: if it weren't for the fact that the Syrian rebels have increasingly been supported, and to a large extent even dominated, by Jihadist elements linked to Al-Qaeda, a limited U.S. "tilting" of the balance of power in favor of the Sunni rebels should have been all but a no-brainer. To argue this point of view as a realist is not to diminish the obvious risks of a potentially catastrophic escalation of any U.S. military intervention, especially in light of America's track record from Vietnam to the second Gulf War. Moreover, given that recent evolution in the composition of the Syrian rebel leadership, the results of even a successful U.S. intervention could well result in recriminations flavored with claims of "be careful what you wish for." This reality will only put more pressure on Obama and the military to help topple Assad with minimum military effort. As a matter of tactical execution, a limited intervention will have to look more like Libya than like Iraq, Afganistan, or, for that matter, Vietnam. Can the Obama Administration and the U.S. military be counted on to "deliver" such a result? We will see, and no doubt the usual pundits will be debating this, like everything else, through their partisan political lenses. But from a realist perspective, the case for a limited, well managed intervention that tilts the balance of power in Syria against Assad has merit. Indeed, it may even be compelling.