As the US military campaign ramps up in Iraq against the Islamic State (IS), many important questions remain unanswered in regard to the operation's imminent counterpart in Syria. It seems clear that US policy in Syria will involve some sort of force on the ground to complement the airstrikes targeting IS positions, heavy weaponry and troops. The Americans have guessed correctly that IS cannot be defeated unless taken out in Syria as well, and airstrikes alone are not enough to do that.

IS has already withdrawn from prominent buildings it took as headquarters in towns and cities such as Raqqa, instead adopting a lower profile and hiding among the locals and abandoning heavy armor for more mobility and stealth via lighter cars and vehicles. The million-dollar question is: Who will take on the role of the peshmerga and the Iraqi army in Syria?

Certainly not the Bashar al-Assad regime, as the US administration has ruled that out entirely. In fact, none of Damascus' powerful backers will be taking part in the anti-IS coalition, something that many observers think is a major mistake and undermines any effort to defeat the powerful and well-entrenched group.

The Islamist rebels are also out of the question, as the majority of them are hostile toward the West and unlikely to welcome any foreign military action in Syria unless it directly targets the regime. Even the jihadist factions locked in a bitter and bloody interfactional war with IS are unhappy at what they view as overt Western aggression, fearing they might be next. The Kurdish militias are unlikely to be considered either, because the Turks are apprehensive about arming groups linked to their own long-running conflict with the Kurdistan Workers Party.