On November 13, 2015, while Turkey was preparing for the G-20 summit, Paris was shaken by multiple terrorist attacks reportedly carried out by Islamic State (IS).French President Francois Hollande called the carnage “an act of war.” Notably, the deadly attack came after Paris’ decision to re-deploy the Charles de Gaulle aircraft carrier for anti- IS missions, as well as Turkey’s repeatedly voiced intention for a more decisive campaign in Syria that would not rule out the possibility of a land incursion.Without a doubt, Ankara’s insistence on establishing a no-IS zone in the northern part of Syria now attracts more attention than ever.The necessity of a dependable ground force Above all, we should understand that no political-military plan to clear IS from the Turkey-Syria border can succeed via an air campaign alone. Theoretical studies on air power’s decisiveness against irregular adversaries have been a matter of debate in military circles for a long time.Although precision-guided munitions and real-time targeting through network-centric capabilities and advanced sensors drastically increases effectiveness of air campaigns, still, counterinsurgency campaigns have to rely on robust ground troop presence for holding the terrain and rebuilding conflict-torn infrastructures.Especially given IS’s depopulation strategy in captured provinces, calculating a true force-to-space ratio would not be easy for such an effort.At this very point Turkey faces a difficult position.Ankara naturally refrains from war scenarios that include PYD involvement because of the Kurdish paramilitary group’s close, organic ties with the PKK terrorist organization.Besides, a land incursion by the Turkish army risks high casualties, while Turkey’s allies seem to be sticking to their “no boots on the ground” policies (albeit results of the recent Paris terrorist attacks remain to be seen). Finally, although Ankara has hinted at plans of a ground operation to be executed by armed Turcoman groups and the Free Syrian Army elements, along with some Iraqi Kurdish peshmerga, such a force’s combat capabilities are highly questionable.Thus, Ankara may soon have to decide between facing an uncontrolled PKK-affiliated Kurdish corridor along its Syrian border and the casualties that could result from using its army as a reliable ground incursion force.Rethinking the mission If Ankara decides to use its own land forces to launch a limited incursion to clear and hold terrain in northern Syria, such a mission would entail significant risks. Firstly, the ongoing debate on a possible military intervention in Syria lacks reliable and intellectually satisfactory discussion in Turkey.In this regard, the current exchange of ideas through columns has centered on how the Turkish armed forces would launch an air campaign followed by a ground operation, without asking vital questions such as the desired political end-state, or considering viable “hold and rebuild” strategies.Yet, lessons learned from the 21st century’s counterinsurgency campaigns suggest that in the absence of crystal clear political goals and perspective even the best tactical and operational successes cannot be translated into strategic victories.Or in other words, such a Turkish incursion could lead to winning the war while falling short of attaining the goals of peace and stability.Second, the Turkish administration should take into consideration the very menacing fact that IS retaliation may not necessarily remain limited to forward-deployed military assets. So far, the terrorist network has attacked a commercial flight from Egypt to Russia to retaliate against the Kremlin’s move to target IS positions around Hama.Likewise, the recent tragic terrorist attacks in Paris came after the French government’s decision to deploy the Charles de Gaulle aircraft carrier for anti-IS operations.Up until now, Turkey has suffered a significant number of civilian casualties due to IS suicide bombings. Moreover, there are strong indications suggesting the presence of several IS sleeper cells within Turkey that could threaten metropolitan areas.Third, although the Turkish armed forces enjoys a good level of experience in low-intensity conflicts due to the decades-long struggle against the PKK, Islamic State poses a categorically different challenge of hybrid warfare, including tactically game-changing capabilities such as anti-tank guided missiles, man-portable air defense systems and intensive urban warfare. The Turkish armed forces already has robust military formations deployed along the problematic Syrian border: the 5th Armored and the 20th Armored brigades as principle maneuver units, along with elite commandos supported by strong artillery assets that can provide fire support up to some 40 km into Syrian territory. These in addition to air bases in close proximity of the Syrian border that would boost sortie rates and on-station times of the Turkish air force. Yet, the hybrid warfare scenario poses enough risk to constrain optimism.More importantly, no one in Turkey talks about the IS’s presently immature yet growing chemical and biological warfare capabilities that could pose anti-access/ area denial threats to some extent. The terrorist group has already been using mustard gas in artillery shells in Iraq and recently in Syria.Furthermore, there are also other menacing signs of some WMD capabilities in IS’s hands. In this regard, in early 2015 US CENTCOM killed one of Saddam Hussein’s chemical weapons experts, Abu Malik, in a coalition air-strike targeting IS positions. Furthermore, in 2014, a laptop captured from an IS-member Tunisian national revealed an instructive document on developing biological weapons, particularly on weaponizing the bubonic plague. Although IS’s chemical and biological warfare capabilities have not reached the point of being capable of disrupting a Turkish land incursion, still, even a small number of casualties from WMD use could deeply shake Turkish public opinion.Last but not least, while the Russian air campaign, which could hardly be described being anti-IS given the target set, is ongoing, coordinating deep air interdiction and close air-support missions in Syrian skies would be problematic.Turkey at a crossroads In sum, the Turkish administration might soon find itself at a critical crossroads. Should Ankara opt for launching a ground incursion in Syria, this would be much different than the cross-border counterterrorism operations of the 1990s due to the capabilities possessed by IS. On the other hand, should Turkey limits its involvement with an airground campaign, it would inevitably witness the rise of the PYD, considering its practical value to the West. Put simply, IS cannot be defeated by the Free Syrian Army and armed Turcoman groups, even supported by the best close air support.Nevertheless, any military option could be initiated if it is a matter of national security.Under these circumstances, the most viable way forward for Turkey is to convince its allies to commit more military resources to contain the IS threat.The author is a research fellow at the Istanbul-based independent think-tank the Center for Economics and Foreign Policy Studies.