Destroying the Islamic State (IS) and limiting the influence of Iran is a difficult project. The United States has more capabilities in Syria than in Iraq to destroy IS and limit Iran. The Sunni Arab tribes of the Euphrates Valley no longer support the Islamic State and are ready to join those who will liberate them, which explains the effectiveness of the Syrian Democratic Forces (Kurdish-Arab) against IS. Thus the liberation of Raqqa could thus take place in fall 2017, provided Turkey does not launch an offensive against the Syrian Kurds.
A serious governance problem will also emerge following the defeat of IS. In Iraq the return of Baghdad's army risks creating the conditions for a new Sunni insurgency. In Syria violence between the tribes and the Kurdish militias must be avoided. Bashar al-Assad and his allies are anticipating chaos in the Euphrates Valley so they can impose their vision of a Pax Syriana.