
Now that the possibility of a US missile strike in Syria has faded, US attention has been diverted to other matters in the Middle East, namely, negotiations with Iran. However, the diminished threat of intervention combined with a weak UN Security Council Resolution has led to a significant loss of US influence among the Syrian opposition. The Islamic State of Iraq and al-Sham (ISIS), one of two al-Qaeda branches operating in Syria, has capitalized on this influence vacuum by attempting to establish its dominance within rebel-held territory. In response to an ascendant ISIS and general frustration with US foreign policy, opposition fighting groups are beginning to form Islamic coalitions independent of the US-backed Syrian National Council. US policymakers will now have to deal with a stronger al-Qaeda presence and less capacity to bolster anti-regime forces.
After the use of chemical weapons by the Syrian regime on August 21, it appeared inevitable
Capitalizing on this is the larger of two active al-Qaeda franchises, ISIS. The organization is actively employing a long-term expansionist strategy with two primary operations. The first is opening many fronts against not only the Syrian regime, but also the Turkish military
a strategy of dropping back—taking rear positions—as rebels with the FSA alliance leave for front lines to fight government forces, allowing ISIS to build a presence in towns and villages left without security or services… As the U.S. threat receded, emboldened ISIS militants ramped up efforts to win local support… They are telling them: ‘We told you that you can’t depend on America for freedom. Don’t be fooled—you only have us.’
If ISIS can establish itself among Sunni Syrians away from the frontlines, they will be able to severely reduce the chances of a scenario similar to the Awakening, a Sunni tribal revolt against al-Qaeda in Iraq that occurred in the al-Anbar province of Iraq in 2006. Additionally, many of the

The Syrian opposition is reacting to ISIS operations and disillusionment with the US by restructuring themselves. While a few former Free Syrian Army (FSA) units have been merging with groups
In the short term, we can expect that Syrian rebel groups will continue to break away from the US-backed Syrian National Coalition and form Islamist coalitions. While it is still too early to tell if these new organizations will give the rebels an advantage over Syrian regime forces, Islamic coalitions do represent a significant challenge to ISIS and its expansionist strategy. It is likely that fighting between the al-Qaeda branch and its rivals will escalate in the short term. The outcome of this infighting will have a major effect on US national security interests in the area. Should ISIS succeed in its campaign, the Sunni enclave within Syria could become a pre-9/11 Afghanistan.
Given this current situation, the US should adopt policy options that reduce ISIS control in Syria. Options include relaxing the vetting requirements to give aid to rebels (especially as many rebel militias are taking on non-secular, Islamist characteristics), giving logistic and intelligence support to rebel groups fighting ISIS, and attempting to repair the damaged relationship with Saudi Arabia. These options would not only halt ISIS strategy, but would regain lost influence among the Sunni rebels and their financiers. Additionally, the US should allocate more resources to Turkey, Jordan, Iraq, and the Kurds to create a stronger containment strategy.