Turkey and Russia in Syrian war: Hostile friendship

This study considers Russian-Turkish relations within the context of the Syrian war. We elaborate on both Russia’s and Turkey’s strategies and their understanding of the Syrian War, and consider how the two countries have managed to stay on the same page despite conflictual strategies and geopolitical interests in Syria. The current literature does not address this question and does not thoroughly compare their actions and engagements in the field. This article aims to clarify Turkey-Russia relations in the Syria and provides evidence of how they are in conflict and cooperate at the same time. In this regard, it is argued that the available evidence indicates that Turkey-Russia relations in Syria operate on the “compartmentalisation” strategy. In order to test this argument, the qualitative research method based on secondary resources is used while the theoretical framework previously formulated by Onis and Yilmaz (2015) is adopted. They conceptualise Turkey-Russia relations as if they do “compartmentalise economic issues and geopolitical rivalries in order to avoid the negative spillover of certain disagreements into areas of bilateral cooperation.” Furthermore, they claim that compartmentalisation can be hindered if there are deepening security concerns in an area like Syria. However, this article underscores that compartmentalisation does not only work by separating the economic issue from geopolitical rivalries; it also makes Turkey and Russia able to cooperate and conflict in a specific and fundamentally conflictual geopolitical issue such as Syria. The convergences and divergences that occurred in the Syrian field are conceptualised under the strategy of compartmentalisation. In this context, the cooperation – the signed agreements and established mechanisms, conflicts, and clashes in the field, are acknowledged as the consequences of the compartmentalisation strategy in Syria. The compartmentalisation strategy is specifically used in Syria in order to avoid the negative impacts of direct clashes in bilateral cooperation and agreements. It can therefore be concluded that the deepening divergence in security related issue does not necessarily prevent compartmentalisation; on the contrary, compartmentalisation paves the way for stabilisation of such deepening divergence.


Introduction
I n March 2011, the war in Syria began as part of the Arab Spring which had firstly ignited in Tunisia at the end of 2010. Although it was primarily started as a peaceful protest for democratic and cultural rights, as well as for more freedom and welfare, after a month passed, opposition groups faced rigid actions from the Assad regime. The increasing civilian death toll and the resistance offered by the opposition aggravated the conditions and angered the central government. In the meantime, the opposition groups started to organise and established the Free Syrian Army (FSA). It progressively became the sole legitimate armed opposition in Syria and got control of a significant proportion of the territory. The opposition, led by the FSA, was primarily supported by the United States (US) for at least two years. At the time, the US even provided an equip-train programme for the soldiers fighting for the FSA.
In 2014, we saw the first dramatic shift in the course of the Syrian war. ISIS ((Islamic State of Iraq and Syria) obtained pivotal influence and got control of the area that was previously captured by the FSA. It coincided with the U.S diverting its support to the terrorist organization PKK's (The Kurdistan Worker's Party) branch in Syria, YPG (The People's Protection Units). A year later, Russia was involved in the conflict alongside the Assad regime which caused the second shift. Its involvement in the crisis got the Assad regime off the hook. Afterwards, Tehran intensified its assistance to the regime. Regime forces had the wind at their back and, together with Russian and Iranian support, started to advance against opposition forces and ISIS. On the other side, the FSA, simultaneously fighting on several fronts, against ISIS, the YPG/PKK, and Russian & Iran backed regime forces, lost power and momentum. In 2016, the war in Syria took another turn when Turkey initiated its Euphrates Shield Operation (ESO). Consequently, together with the Turkish Armed Forces (TAF), FSA forces heaved a sigh of relief and recaptured territory in North Western Syria (Azez-Jarablus-El Bab line). The operation was conducted against the terrorist threat from ISIS and the PKK; yet, it raised concerns in Moscow regarding its ties with the PKK in the regions in the Western Euphrates. It also did not want the TAFbacked FSA to gain power against the Assad regime. On 20 December 2016, a ceasefire agreement was signed between Turkey and Russia. It was followed by the so-called Astana trio/mechanism established by three countries, Turkey-Russian-Iran, and the declaration of the four de-escalation zones (Aljazeera, 2017). It was the first instance of cooperation despite the conflictual positions in the field and was took place after a normalisation process (Nissenbaum, Peker and Marson, 2015).
Within the framework of the Astana Mechanism, Idlib was also included in the designated de-escalation zones. In this regard, Turkey became the guarantor of the opposition groups in Idlib and conducted operations towards the region. Similarly, it was carried out despite the counter-opinions prevailing in Russia and its ally, the Assad-regime. Almost a year later, Turkey conducted a follow-up operation to secure the Afrin region. The operation, called Olive Branch, mainly targeted the areas under PKK-control backed by Russia. Russia had tried to break a deal between the PKK and the Assad regime; it tried to convince the PKK to retreat to leave the Assad regime in control. Having experienced a reluctance from the PKK side, it approached the Turkish operation as an opportunity to kick out the PKK from the Western Euphrates as well as the US influence. Together with these operations, Turkey blocked the PKK's desire to achieve coastal control over the Mediterranean Sea via Aleppo, Idlib, and Latakia (Balanche, 2016) and prevented a PKK-oriented corridor; increased its border security, and eliminated the ISIS threat near its borders and inner territory. Subsequent to the latest operation, Idlib once again became an issue on the agenda for Turkey and Russia. The two countries were able to build trust and signed a memorandum for stabilisation in Idlib. The operations were conducted by Turkey despite the Russian-Assad regime's dissidence, but despite this they were able to cooperate against the PKK and signed the Sochi agreement over Idlib. The conjuncture that occurred after the Olive Branch Operation represented the second instance of cooperation.
In October 2019, the course of the Syrian war experienced another shift following Turkey's Peace Spring Operation. On the one hand, it was crucial for Turkey's national interests and security considerations. On the other hand, it was not against Russian interests to see US troops retreat towards the south and foregoing territorial control. Also, it was seen as an opportunity to create a power vacuum. Moscow also saw a window of opportunity to jump over the North-Eastern part of Syria. In the end, it was not the US but Russia who was involved in the operation process. On October 22 nd , Turkey and Russia signed a memorandum of understanding in Sochi. This was a clear indication of the improvement of bilateral relations and cooperation in the Syrian field. However, the cooperation between the countries was followed by a confrontation in the field. As such, at the very beginning of 2020, regime forces backed by Russian air forces and Iranian militias intensified their attacks towards Idlib and Aleppo. Whilst the artillery over the region continued, they started to target the TAF. As a result, 17 soldiers were killed between 3 and 26 February. As of February, clashes escalated and the TAF increased its fortifications. On 27 th February, an irreversible paradigm shift took place when Turkey lost 36 soldiers as a result of an air attack conducted by the Assad regime-Russia alliance. It escalated further, if not peaked if it was not the culmination of the conflict, and complicated circumstances in Idlib and brought another operation initiated by Turkey, the Spring Shield Operation. The two countries, besides the indirect and several other small-scale confrontations through their proxies, were in direct conflict in the field. The operation was concluded with an additional protocol to the memorandum on stabilisation of the situation in the Idlib de-escalation area. This is a rather unique instance of two countries cooperating despite military confrontation in the field. They somehow managed to find themselves moving in the same direction.
When it comes to Turkey-Russia relations, there is a clear historical pattern for both conflict and cooperation. In this context, the aid provided for Turkey by the Soviet Union, improvements in Turkey's heavy industry with the help of Soviet investments, trade agreements and economic cooperation existed on the one hand, whereas geopolitical conflicts over the straits, Central Asia, and Caucasus existed on the other (Hirst and Isci, 2020). The two countries have been able to pursue dialogue despite the fundamental geopolitical struggles. The past legacies are important when explaining the current dynamics of bilateral relations. Also, the established strategic partnership; interdependence; economic and industrial investments; common interests; strategies designated by both sides, to a certain extent, play a role that prevents the collapse of bilateral relations where Syria is not the only area where they clash. Current literature does address Turkey-Russia relations and the limits of their geopolitical alignments in Syria (Köstem, 2020); yet, it fails to elaborate on the main drivers of their strategies and how they both clash and cooperate at the same time. This article offers the broadest and richest assessment of both countries' policies and engagements concerning Syria.
Turkey-Russia relations, in general, have been elaborated upon within the framework of compartmentalisation. They were conceptualised by Onis and Yılmaz (2015) and further improved by Duzgit, Balta and O'Donohue (2020). While assessing bilateral relations, Onis and Yılmaz (p. 2) suggest that "a strategic partnership will be difficult to forge and consolidate as long as significant differences persist in the geopolitical orientations and political outlooks of the individual states." In this regard, compartmentalisation is acknowledged as a strategy that (Onis and Yılmaz, 2015, p. 2) "enables the coexistence of political tensions with deepening economic ties." As such, the Syrian case is analysed in this context, in which both countries have conflicting relations; yet, they do not let the disagreements over Syria harm bilateral economic cooperation (Onis and Yılmaz, 2015). Turkey's politics over Ukraine and Crimea are similarly approached and it is claimed by the authors that (Onis and Yılmaz, 2015, p. 17) "the opposing positions of Turkey and Russia in the context of the Syrian and Ukrainian crises aptly illustrate… although such conflicts exist, and while they hamper political relations, they do not significantly undermine the seemingly robust economic relationship built thus far." And it is conceptualised as such (p.17): "One important strategy that has emerged in this period is the tendency to compartmentalise economic issues and geopolitical rivalries in order to avoid the negative spillover of certain disagreements into areas of bilateral cooperation." Nevertheless, compartmentalisation is claimed to have been impeded when there are deepening security concerns such as in Syria. Duzgit, Balta and O'Donohue (2020) also argue that the asymmetries in economic and political relations in Turkey-Russia relations prevent the compartmentalisation of disagreements. According to them, the difference in exit cost and power asymmetries limit such a compartmentalised strategy. They believe that this strategy is very significant; however, "[u]nder conditions of asymmetric interdependence, compartmentalisation is not a stable equilibrium: the stronger party can always threaten to cease compartmentalising and inflict unequal harm to achieve a desired outcome" (Duzgit, Balta and O'Donohue, 2020). It is suggested that "Russia has the choice to compartmentalise; Turkey, by contrast, cannot shrug off the exit costs associated with choosing not to do so" (Duzgit, Balta and O'Donohue, 2020). They further investigate Turkey's involvement in Syria, the Idlib crisis, and Turkey-Russia relations in Syria. It was conceptualised under diplomatic and tactical challenges; nonetheless, it was not analysed within the context of compartmentalisation strategy (Duzgit, Balta and O'Donohue, 2020).
This article adopts Onis and Yılmaz's compartmentalising strategy into the Syrian case. Unlike the prevailing approach and already provided conceptualisation in a broader sense of the bilateral relations between Russia and Turkey, this study suggests that the two countries have successfully achieved the compartmentalisation of disagreements even if they caused direct military clashes in the field and deepened security concerns. This strategy prevents the bilateral cooperation being negatively affected/broken off, especially in Syria. This strategy is recognised as the answer to the question of how they have managed to cooperate while being pitted against each other in Syria. Having adopted a compartmentalising strategy; the Astana trio/mechanism, the agreement on the establishment of de-escalation zones of May 2017, two Sochi Agreements of September 2018 and October 2019, as well as the agreement on Idlib of March 2020, are conceptualised as cooperation that has been achieved in Syria. While Turkey's operations in relation to the Syria-Euphrates Shield Operation, Olive Branch Operation, Peace Spring Operation, and Spring Shield Operation are categorised as sources of the disagreements.
The focus of this essay is on assessing conflict and cooperation (Turkey's operations, the ceasefire agreement, and diplomatic mechanisms briefly mentioned above) between the two countries in the Syrian field. The purpose of this article is to conceptualise the relationship between them. To this end, the first section explains the factors that determine Russian foreign policy pursued in Syria. In this context, it elaborates on the drivers behind the actions and, in general, the understanding of Moscow. As such, this part builds upon the legacy of Primakov, history, identity, and geopolitical interests as the main drivers behind Russia's Syrian policy and analyses Russia's actions in the Syrian war. The second section provides a broad perspective regarding Turkey's strategy and actions in Syria. Here, the policies of safe zone creation, counterterrorism, and preemptive strategy are examined. The third part examines cooperation and conflicts as the sources of amity and enmity. They are investigated under the context of the national strategies of the two sides; relatedly, their causes and consequences are explained. In this context, major Turkish operations and all kinds of diplomatic initiatives are assessed in order to conceptualise the bilateral engagement.

Russian Understanding of Syria: From Primakov to Geopolitics
A t the outset, Russian intervention in Syria was a calculated risk, rather than an unplanned action (Clarke and Courtney, 2019;Kofman, 2015). With this involvement, Russia managed to stand up to the US in its first military operation beyond its sphere and reasserted itself as a major power. Syria is a vague demonstration of the Primakov doctrine (Ng and Rumer, 2019). Thus, everything we observe today is not an idiosyncrasy of a new foreign policy vision but an extension of Primakov's vision. In fact, Russian Middle East policy fundamentally depends on the legacy of ex-Prime Minister, ex-Foreign Minister, and former head of domestic and foreign intelligence, Yevgeny Primakov. His pragmatic, patriotic, Russian national interests-oriented policy visions, and ambition to make Russia a great power coincide with the modern Russian foreign policy. Primakov's legacy aims to establish a multipolar world order against the US; to accomplish a more balanced and complex foreign policy; to expand towards the Middle East; and to balance Western influence in all regions where Russian geopolitical interests exist (Bernier, 2018, pp. 1-30). Current Russian foreign policy and the decision to intervene in Syria have their roots in Primakov's legacy.
Beyond the vision and practice of Primakov doctrine, Soviet Legacy assumes a pivotal role in the formulation of Russia's Syrian and Middle Eastern policy. Primakov represents the Soviet legacy by himself; yet, the Soviet Union's historical ties with Syria and its long-lasting regime lay the foundation for the Kremlin's Syrian policy. Relatedly, the Syrian identity shaped by the Baath ideology, which has its roots in the Cold War period, is regarded as one of the most significant aspects of Russia-Syria relations. Baath's ideology has been built on three core ideas: anti-imperialism, secularism, and socialism (CIA, 2002). It mainly aims to expel Western influence from the country and sympathises with the ideas and policies promoted by the Soviet Union. Therefore, over such commonalities and through the established other/enemy, the two countries have been pursuing high dialogue regardless of any kind of disagreements.
Another decisive factor in Russia's Syrian policy is the geopolitical interests which are in line with the Primakov doctrine, historical legacies, and identity. In this regard, several top priority geopolitical interests can be identified. First and foremost, confronting US and Western influence in the region (Casula and Katz, 2018, pp. 295-311). This goal is very much related to Primakov's legacy and the impacts of the strategies exposed after the Second World War, e.g. containment policy. The containment policy designated by George Kennan aimed to contain Soviet influence beyond its borders (Office of the Historian Foreign Service Institute United States Department of State, no date). In this regard, the US got into competition with the Soviet Union over the Middle Eastern countries i.e. Iran, Iraq, Syria, Egypt, to secure energy supply security to Western Europe and control over the Middle Eastern market (Painter, 2010, pp. 486-507). It was also a part of the Cold War competition over the Global South. Having experienced such policies, Russia adopts strategies that are counter-containment oriented as well as to counter-balance US influence in the region. Besides, it was crucial for Russia to withstand US policies to demonstrate its status in the international arena. Confronting US influence is acknowledged by Russia as a way to break American hegemony.
In this regard, protecting its historical ally, Syria, specifically against US policies is of pivotal importance for Moscow. The second interest that can be given under the geopolitical axis is the war on terror and keeping/eliminating the terror threat away from its borders. In fact, policymakers in Moscow have been concerned at the spread of terrorist organisations within its borders. They see the radical groups operating in Syria as a potential threat and tie them to the Muslim population living in Russia (Freedman, 2010). These concerns are very much relevant for other Middle Eastern and Central Asian countries. There are approximately 15-20 million Muslims in Russia (The Moscow Times, 2019), in addition to memories of two consequent Chechen wars (Freedman, 2010). Therefore, it attributes greater importance to curbing this socalled potential threat in distant geographies. One last interest that can be specified is the arms market in terms of economic and political influence. Countries like Syria, experiencing a huge ongoing internal crisis and being a close ally of Russia, stand as an important partner in terms of the arms trade. Even though its economy is relatively small to bring economic surplus when it comes to arms or any kind of bilateral trade, it constitutes a significant amount of political influence and eliminates other from the dominance of such countries. Moreover, it gives the exporter country an opportunity to test its weaponry and to prove its success (TASS, 2017), which may in return trigger, if not boost, the demand from other countries.
Keeping these factors and reasons in mind, Russia has sided with Damascus since the very beginning of the Syrian crisis. Russia's involvement in the crisis marks the first intervention of the Russian Armed Forces outside the borders of the former Soviet Union. It is also referred to as "Russian resurgence in the Middle East" (Melamedov, 2018, pp. 1-9;Petkova, 2020;Rumer, 2019). Although securing its ally in the region seems like the main reason behind the interference, Russian intervention has causes that vary from Primakov's legacy to geopolitical interests as specified above. Indeed, the Syrian Civil War has significantly speeded up and deepened Russia-Syria engagement. The ongoing crisis has primarily provided Russia ground to consolidate its physical presence in the Middle East and the Eastern Mediterranean by conserving the Assad family's rule. In other words, the civil war provided a suitable base for Russia's physical reappearance in the country. Even though it would be wrong to assume that Russia would not have regained its strongholds in Tartus and Latakia if it was not for the crisis, the war and intervention had significantly boosted the process. To elaborate further, prior to the war, bilateral naval cooperation was renewed and further developed. As a result, a small naval logistics facility in Tartus has been under expansion since 2009. Until today, Tartus remains Russia's only naval facility outside the former Soviet Union. When the Arab Spring started to turn into Arab Winter, ISIS increased its presence and solidified its power; it was directly threatening Russia's regional interests. It was faced with the possibility of losing its last stronghold, Syria, as a military stronghold including the ones in the Eastern Mediterranean. Direct military interference presented a significant opportunity for consolidation of previous acquisitions and open up a way for the establishment of the Hmeymim airbase in Latakia. Two years after the intervention, Russia's presence in Syria was consolidated. In 2017, treaties establishing a permanent Russian presence in the Eastern Mediterranean by securing the Tartus and Hmeymim facilities in Moscow's possession for the next 49 years with a right to extension for 25-year periods on a free of charge basis (Suriye Gundemi, 2020). The validity of the agreements is in direct correlation to the survival of the current regime; hence, another reason behind Moscow's concern over the preservation of the current regime. In summary, Syria's relative distance from the West, the secular character of its governance, as well as a rich background of cooperation with Soviet Russia, which granted the latter access to the Eastern Mediterranean, shaped Russian policy in the Syrian Crisis and has not only an economic and political, but primarily a strategic character.
Russia's military assistance to Damascus has actually been taking place since early 2012 (Galpin, 2012). However, only a direct military engagement of the former reversed the conflict in favour of the regime, which would not have survived it was not for Moscow. The regime had lost control over the populated areas in provinces like Idlib, Aleppo, Raqqa, Deir Ez-Zor, Deraa, and Quneitra (Petkova, 2020). Furthermore, Damascus had been struggling to sustain its control over the countryside near Hama, Homs, and Damascus (Petkova, 2020). As a result of 4 years of political mayhem, Damascus had around 25 percent of the Syrian territory under its control at the time of Moscow's direct military involvement in September 2015. Currently, as a result of Russian military support, the regime has regained control over the most of the country with the exception of the South-Eastern part of the Euphrates and the last de-escalation zone of Idlib.
Following the interference in 2015, Moscow concluded that sole military assistance would not be enough to regain the territory and to secure internal stability in post-war Syria. Henceforth, reformation of the regime's forces has been essential for both the security of the current regime and the internal stability of post-war Syria. As a result, the Russian Ministry of Defence (MoD) had undertaken a number of short-and mediumterm measures to strengthen the regime forces. Initial measures included the creation of the 4th and the 5th Army Corps as well as the provision of high command training (Sayigh, 2020). Hence, by 2017, Russian senior military professionals had penetrated almost all units of SAA. The Russian MoD envisages lack of institutionalisation, politicisation, sectarisation, as well as ideology, as the major factors hindering a successful reformation of the regime forces in the long term (Khlebnikov, 2020). Apart from the need for reformation of the armed forces, Moscow realised that Syrian security services required major alterations (Semenov, 2020). Otherwise, the competition between various security bodies that exist could lead to the emergence of internal conflicts in a post-war Syria making the country prone to falling into a vicious circle once again.
Even though it reversed the course of events in favour of Damascus, Russia has faced several challenges since it interfered in Syria. First of all, a direct military intervention happened to cost way beyond expectations: the intervention took years instead of months as planned. When intervening in the Syrian Civil War in September 2015, Russia expected a quick victory within a time-lapse of 3-4 months (Lavrov, 2020). Currently, Russia's physical presence in Syria is maintained at high expense for the former, estimated at around 5 billion dollars. Nevertheless, the altered dynamics and acquisitions following the involvement are in line with the strategic planning.
Overall, the year 2015 symbolises a significant breakthrough not only for Russia's Syrian or Middle Eastern policy but also for the entire foreign policy direction. It aimed to and successfully improve its image in the international arena, strengthen its power in the Mediterranean, balance the increasing influence of the USA through the YPG/ PKK in Syria, and prevent the fall of its ally. In doing so, Russia, as mentioned above, has obtained both short and long-term political, military, and economic goals. It has also managed to keep up with the competition for influence in the Middle East. Strategies adopted by Russia after 2015 have become more proactive, if not more expansionist, and proved that it has the power to affect the course of the war. Relatedly, in the 2016 foreign policy concept document formulated by Russia, Syria was included under the prioritised issues and regions. Russian forces have become one of the decisive actors in the Syrian war. Moscow strengthened its military presence in the Syrian field together with its air and land bases, as well as its expanded operational area. It is known that Russia has more than 45 military points under its control. All in all, its influence has reached a certain point that makes it the primary actor in the course of the Syrian war.

Turkey's Approach to the Syrian War: Safe Zone Creation, Counterterrorism, and Pre-emptive Strategy
T he primary approach adopted by Turkey after the inception of Arab Spring was to promote the democratic demands voiced by the Syrian people and to assume a conciliatory role between the Assad regime and the opposition. The focus of the international coalition, naturally so like Turkey's focus, was on the overthrow of the Assad regime. At the time, Turkey, especially considering the extent of the power and control they enjoyed, was convinced that the Assad regime would be overthrown by the opposition.
However, the course of the Syrian civil war experienced a shift when the militants who once fought side by side with Al Qaida in Afghanistan escaped from the prisons in Iraq and Syria. Those militants were organised under the umbrella of Syrian al-Qaida and later on established the well-known terrorist organisation ISIS. Following the rise of ISIS and its land acquisitions, the international coalition diverted its efforts to restrain ISIS instead of removing the Assad regime. FSA-lead opposition forces started to lose material support, whereas ISIS piled up its field advancements vis-à-vis other actors. In the meantime, Assad was caught in a very limited space and invited Russian forces to intervene, which caused another shift in the course of the Syrian war. Several months after Russian involvement, Turkey downed a Russian fighter jet which prompted a diplomatic crisis. It happened at a time when Turkey had no air defence missile system due to the withdrawal of Patriot missiles from Turkey. Having suffered the rupture that occurred in the bilateral relations and change of US attitude in the course of the Syrian war, Ankara was forced to take more pragmatic steps.
On the one hand, both the PKK and ISIS intensified their attacks within Turkish borders, on the other hand, Turkey experienced a failed coup attempt organised by the FETO (Fethullah Terrorist Organization). Furthermore, a simultaneous increase in US assistance provided for the PKK's branch in Syria, YPG, dramatically changed Turkey's priorities in the Syrian civil war. These factors indeed caused an alternation in Turkey's threat perception. From 2016 onward, Turkey prioritised the elimination of terrorist organisations rather than the overthrow of the Assad regime. Certain policies and steps taken by the US government such as economic policies, the harsh rhetoric of the Trump Administration that escalated certain disputes, the PKK, FETO, and the Eastern Mediterranean, were considered by Turkey as threats to its national security and interests. Whilst Russia emerged as a balancer and a significant alternative for cooperation. Such negative conjuncture perceived by Turkey drove Ankara to Moscow and brought relatively smooth rapprochement following the jet crisis. Indeed, the revival of the Akkuyu Nuclear Power Plant Project, the purchase of S-400 air defence systems, and the TurkStream project signed in 2016 are illustrations of such foreign policy rotation.
From 2016 on, Turkey adopted more realist and pragmatic policies rather than idealist ones to maintain its national security. In this regard, two strategies come forward: elimination of terror threats across borders and creating safe zones to prevent further refugee influx. Both strategies were designated and applied with deep consideration for its national security. To this end, Turkey conducted four main operations in Syria: the Euphrates Shield Operation, the Olive Branch Operation, the Peace Spring Operation, and the Spring Shield Operation.
As a starter, on August 24, 2016, Turkey initiated the Euphrates Shield Operation to eliminate plans for establishment of a terrorist organisation along the Turkish borders of Syria which was accelerated following the seizure of Membij by the YPG/PKK on August 12, 2016. The increase observed in ISIS activities and attacks inside Turkish borders also forced Turkey to take more solid actions with regards to national security. In this context, the operation was conducted to ensure border security, to support coalition forces in their fight against ISIS, to prevent the possible capture of the areas under ISIS control by other terrorist groups such as the YPG/PKK, to contribute to the territorial integrity of Syria, and, lastly, to create a safe zone for people forced to flee their homes. The Euphrates Shield Operation can be used to analyse Turkey's strategies in terms of safe zone creation, counterterrorism as well as the preemptive measures taken in this context. Primarily, this operation proved that Turkey would not remain unheeding when it faced an imminent national threat such as ISIS terrorist attacks in its homeland. Secondly, it showed it was able to deter terrorist organisations. Thirdly, it fulfilled the obligations assumed under the framework anti-ISIS coalition with this operation. Fourthly, with the capture of Al-Bab, it was possible for opposition forces to advance against Aleppo, which intensified the pressure on the Assad-regime. Also, with the Azez-Jarablus line under control, it increased Turkey's authority for ensuring border security. Turkey cleansed not only its borders but also NATO's borders from the ISIS threat. As a result of this operation, ISIS militants were moved 40 km away from the Turkish border. Secondly, it increased the reputation of opposition forces backed by Turkey and proved that the YPG/PKK were not alone in fighting against ISIS.
Secondly, the Olive Branch Operation was conducted as a follow-up to further eliminate the terrorist threat across the borders. Another instance for Turkey's safe zone creation, counterterrorism, and preemptive war strategies. Turkey, as a result of the previous operation, eliminated the existence of ISIS in that region and got the Azez-Jarablus line under its control which prevented possible integration of Membij and Afrin, the two regions under YPG/PKK control at the time. In the meantime, the US diverted its support to the PYD/YPG under the umbrella of SDF by claiming that it had no ties with the PKK. The main reasoning behind the support was claimed to be the fight against ISIS. However, supporting YPG/PKK to eliminate ISIS, constituted a threat to Turkey's national security. YPG/PKK militants crossing the border to Turkey through the Amanos Mountains and their indiscriminate attacks against Turkish settlements made it necessary to conduct another operation towards Afrin. Turkey, by conducting the Olive Branch Operation after the Euphrates Shield Operation, prevented a terror corridor along its borders and cleared Afrin from the terrorist groups. It had fortified border security. Notwithstanding this, Turkey showed its commitment to Syria's territorial integrity.
Thirdly, to maintain its national security, to remove the YPG/PKK threat from the borders in the northern part of Syria, to create a safe zone along borders and by doing so providing an opportunity for the Syrian refugees who would like to return to their country; the TAF together with the FSA/SNA forces (Tok, Temizer and Karacaoğlu, 2019) conducted an operation in the Eastern part of the Euphrates. As a result of the Peace Spring Operation, an area of 4.160 km 2 , including Tal Abyad and Rasulayn district centres, was cleared of terrorists. Following the agreement with the US for the creation of a Safe Zone, Turkey's President Recep Tayyip Erdoğan paid a visit to Moscow to meet with his counterpart, Vladimir Putin. As a result of the meeting, the two countries signed a memorandum that signified the end of the operation. In this context, TAF and FSA/ SNA forces remained in the areas they had taken under control; yet, for regions outside the line of Tal Abyad-Rasulayn, Russia promised to ensure withdrawal for the YPG/PKK elements away from the Turkish border at a distance of 30km. To ensure that, a decision was taken to create joint patrols in the areas of up to 10km from Turkish borders, except the city center of Qamishli. As a result, Turkey gained significant experience in terms of hybrid warfare during the operations started by Euphrates Shield Operation and further continued by Olive Branch Operation and Peace Spring Operation.
Finally, Idlib has been one of the priorities for Turkey, -because it has a big population and could be the cause of a further refugee influx, as it has been for the Assad regime and its allies as being the last stronghold for the opposition forces. Thus, it has been one of the regions where the Assad regime together with its allies has carried out intensified attacks. In particular, as a result of the wave of attacks launched by the regime forces and its allies on May 6, 2019, many Syrian civilians lost their lives and were injured. Whilst around 1.5 million people in Idlib fled their homes, they either remained in Idlib or fled to regions where the Euphrates Shield and Olive Branch operations were conducted. Although there are signed agreements and ceasefires declared by the three guarantor states of the Astana process, in order to maintain peace in Idlib, the Assad regime and its allies, two of the guarantor states of the Astana process, namely Iran and Russia, have continued to take an aggressive stance towards Idlib and adjacent regions. As such, in violation of the memorandums of understanding (The Ministry of Foreign Affairs of the Russian Federation, 2017; Voltaire Network, 2018), air forces of the Russia-backed Assad regime were carried out an attack against the TAF's soldiers on February 27, 2020, and 36 soldiers died as a result of that attack. Thereupon ensuring the security of Turkey's observation points and preventing further deterioration of the humanitarian crisis, TAF initiated the Spring Shield Operation on the same day that Turkish soldiers were killed. Consequently, the TAF and FSA/SNA took control of an area of 3394 km2. On March 5, 2020, Turkey and Russia signed an additional protocol to the memorandum on stabilisation of the situation in the Idlib de-escalation area (The Ministry of Foreign Affairs of the Russian Federation, 2020). Henceforth, Turkey and Russia performed nine joint land patrols over the M-4 highway. Although the entire Idlib province could not be secured as a result of this operation, a significant part of the region has become a safe haven through which a new wave of refugees, threatening both Turkey and Continental Europe, was prevented.

Cooperation and Conflict over Syria
S trategic goals and decisive factors behind Russia's and Turkey's approach to the Syrian war have fundamentally clashed. As stated, Moscow has been supporting actor(s) that have been recognized as an existential threat by Turkey. On the other side of the coin, Turkey has been rooting for the actor(s) that are acknowledged as an existential threat by Russia and its ally, the Assad regime. Therefore, the two sides have often come into conflict in the field. These conflicts mostly occur in terms of proxy-wars where Turkey and Russia are not directly targeting each other. The word is chosen because the territories and bases under TAF control have been targeted several times despite the various agreements and protocols signed between the two countries. During the last Idlib clashes, TAF land forces were directly targeted. That attack caused the deaths of 36 Turkish soldiers. It has been reciprocated where TAF has targeted Russia-backed regime forces and caused Russian casualties. Looking at the constant field confrontations, it is very hard to imagine that the two countries can cooperate on issues related to the region. Nevertheless, considering established diplomatic mechanisms and the signed agreement between the two countries, their ability to cooperate can be recognised. In this section, only major conflicts and cooperative diplomatic efforts will be analysed by acknowledging there are various issues left outside the context of this article.
The two countries have confronted each other on multiple occasions. First of all, Turkey's Euphrates Shield Operation caused tensions when Russian soldiers shielded YPG/PKK militias against TAF's advances. Notwithstanding, the regime forces did not wish to see gains in TAF's field control with the FSA. Furthermore, Moscow's insistence over Assad's inclusion in Turkey's safe zones causes conflicts between Ankara and Moscow. Similarly, during Turkey's Olive Branch Operation, Russia positioned its military in the Tal Rifaat region, particularly preventing TAF's field advancements. Furthermore, Moscow intervened in Turkey's operation conducted in the Eastern Euphrates (Peace Spring Operation). It was no one but Moscow who convinced Turkey to stop the military operation and to sign a ceasefire agreement. In the meantime, Russia utilised the power vacuum opportunity to position its forces and has not fulfilled the promises given regarding the retreat of YPG/PKK forces. This was another instance of Moscow's concern in terms of Turkey's field gains vis-à-vis regime forces as well as an example once again of Moscow shielding the PKK's existence. Each time, there is a pattern for conflictual interests which indeed deeply affects Turkey's security concerns. Moreover, the last clash that occurred in March 2020 was an example of the two countries cutting each other's throats. It occurred despite the signed agreements and ceasefire aimed at peace and stability in Idlib. They have been indirectly fighting through the proxies supported in the field or by preventing each other's field goals; however, the Idlib case provided an instance where the TAF was directly targeted by the Russian/Assad regime's air forces. It was also important for being the most catastrophic instance in terms of the casualties which later on turned into another Turkish operation. During the Spring Shield Operation, TAF and FSA/SNA forces fought against regime forces and it ended up with an agreement between Turkey and Russia. Every time they got into a fight or Turkey initiated an operation against a Russian ally and Moscow's regional interests, there occurs some kind of diplomatic mechanism or a ceasefire agreement between Ankara and Moscow.
In fact, Russian-Turkish Syria cooperation has resulted in a number of essential agreements as well as negotiation mechanisms currently shaping the situation/status quo on the ground. The Astana trio/mechanism of 24 January 2017; agreement on the establishment of de-escalation zones of May 2017, two Sochi Agreements of September 2018 and October 2019, as well as the agreement on Idlib of March 2020, are the most critical in the Syrian crisis' trajectory.
At the outset, as a consequence of the meetings between Turkey, Russia and Iran held in Astana, a mechanism was established to support and monitor the ceasefire. With the realisation of the importance of diplomatic means, the Astana process has become one of the major diplomatic initiatives in the region. It is a negotiation platform providing an alternative to the Western efforts to resolve the conflict i.e. the Geneva negotiations. While the Geneva platform has been initiated by the United Nations, the Astana process became the brainchild of Russia, Turkey, and Iran, as the guarantors of the ceasefire regime in Syria. It mainly presents a non-Western approach to a potential settlement. The foundation for the process was laid out during a trilateral meeting in Moscow on December 20, 2016 (The Ministry of Foreign Affairs of the Russian Federation, 2016). The four deescalation zones in Syria, explained below, were established within the Astana framework. Having massively relied on military means to turn the events in Assad's favour, Moscow, via the Astana process and trilateral summits, indeed acknowledged the importance of diplomacy in a crisis settlement.
Secondly, there is the memorandum on the creation of de-escalation areas in Syria of May 4, 2017. Russia, Turkey, and Iran, as the guarantors of the observance of the ceasefire in Syria, concluded a memorandum on the creation of de-escalation areas in Syria (The Ministry of Foreign Affairs of the Russian Federation, 2017). The memorandum envisaged the creation of de-escalation areas in Idlib province, Homs, eastern Ghouta, and Southern Syria (Deraa and Al-Quneitra) with the purpose of ending violence, improving the humanitarian situation, as well as creating favourable conditions for a political settlement of the conflict. The formation of these de-escalation areas and security zones was a temporary measure with an initial duration of 6 months. Additionally, the memorandum obliged three guarantor states to continue to fight against ISIS, Nusra Front, Al-Qaeda associates both within and outside the de-escalation zones. Since 2018, the territory of three of the initially established de-escalation zones including Ghouta, Homs, and Deraa has come under the control of Damascus.
Thirdly, on September 17, 2018, amid the Assad regime's assault on a major opposition stronghold Idlib, the memorandum of understanding on the stabilisation of the situation in Idlib's de-escalation zone, also known as the Sochi Agreement, was signed by Russian Defence Minister, Sergei Shoigu, and his Turkish counterpart, Hulusi Akar (Voltaire Network, 2018). The memorandum on the creation of de-escalation areas in Syria of May 4, 2017, formed a basis for the Sochi Agreement. Both Russia and Turkey agreed on a number of measures needed to be taken to stabilise the situation in Idlib. The two agreed that Turkish observation posts in Idlib would be preserved. Russia would take measures to ensure that the status quo in the province was maintained and attacks averted. Furthermore, the sides agreed on the establishment of a demilitarised zone, 15-20 km deep in the de-escalation area. Additionally, the agreement envisaged that all terrorist formations would be removed from the demilitarised zone by October 15. Moreover, the memorandum covered the withdrawal of all heavy artillery of all conflicting parties from the demilitarised zone by October 10. The Turkish Armed Forces and military police of the Russian Armed Forces would conduct coordinated patrols within the boundaries of a demilitarised zone. Finally, the Sochi Agreement envisioned the restoration of transit traffic on the M4 and M5 highways by the end of 2018.
Fourthly, on October 22, 2019, a memorandum of understanding between Turkey and Russia concerning Syria was signed. The sides had agreed upon the shared goals of preserving the political unity and territorial integrity of Syria, as well as protection of Turkey's security concerns (Official Internet Resources of the President of Russia, 2019). The two agreed to establish the status quo in the Operation Peace Spring area that covered Tel Abyad and Ras al-Ayn, with a distance of 32 km. Ankara and Moscow underlined the importance of the Adana Agreement, with Russia taking responsibility for its implementation. Furthermore, the agreement covered the entry of Russian military police and Syrian border guards along the Syrian side of the Syrian-Turkish border (outside the area of the Peace Spring Operation) to remove and disarm PKK/YPG elements to a distance of 30 km. Furthermore, joint Russian-Turkish patrols would take place in the west and the east of the area of the Peace Spring Operation. The two agreed on the removal of all YPG elements from Manbij and Tal Rifaat.
Lastly, on March 5, 2020, as an outcome of Erdogan's visit to Moscow amid the latest escalation in Idlib, an additional protocol to the memorandum on stabilisation of the situation in the Idlib de-escalation area was concluded by Russia and Turkey (The Ministry of Foreign Affairs of the Russian Federation, 2020). The memorandum of 4 May 2017 as well as the Sochi agreement of September 28, 2018, similarly laid the foundation for the protocol. On March 5, Turkey and Russia agreed on a ceasefire in the Idlib de-escalation area and on the establishment of a security corridor 6 km distance to the north and 6 km distance to the south from the M4 highway. Furthermore, the protocol envisaged joint Turkish-Russian patrolling along the M4 highway beginning on March 15, 2020. The protocol was concluded as a result of heavy regime assaults on Idlib since December 2019.

Conclusion
T his article is the broadest and most comprehensive research that investigates Russian-Turkish relations and the main drivers of their policies within the context of the Syrian war. It mainly assesses the sources of conflict and cooperation between the two countries. To sum up, conflict, specifically in the Syrian theatre, is a crystal-clear aspect in all the steps taken by both sides. Such actions seem inevitable since the supported sides and the interests are principally clashing. The stance adopted by Moscow and policies pursued by Russia have fuelled Turkey's security perceptions -to the extent that it was regarded as an existential threat. Moreover, Russia provided a shield for the YPG/PKK on several occasions, even exacerbating the conflictual relations, and gave Russia the opportunity to hold the terrorism card against Turkey. Even though the conflicts and confrontations in the field, regardless of the means used or the course of actions, the two countries managed to collaborate. The Astana mechanism and all the agreements explained above demonstrates their ability to cooperate and the function of compartmentalisation despite clashing national interests and militaries in the field. In this context, we argue that Turkey and Russia are compartmentalising their policies in Syria; they do not let their field confrontations negatively impact or fundamentally obstruct their collaboration in Syria. As a consequence of this strategy, the negative spillover effects from a source of geopolitical rivalry are prevented; however, as this study suggests, not on the bilateral economic relationship but again on the same conflictual, security-related issue i.e. Syria. This article contributes to the literature by showing that compartmentalising can be and is utilised by countries (Turkey and Russia) over the same issue that is related to geopolitical rivalry/ concern of security.
As of today, Syria is divided into several zones of influence. The majority of the territory is under the control of the regime and its allies. Turkey is physically present in the areas adjacent to it that include Tel Abyad, Ras al-Ayn, Afrin, Cerablus, and an opposition stronghold, Idlib. At-Tanf and adjacent to its territories, where the Rukban refugee camp is situated, is under American control. Tel Rifat, Ayn al Arab, and on the Eastern bank of the Euphrates are predominantly under YPG control, with the exception of Haseke and Kamishli, where the regime has authority. Currently, the regime controls over 60 percent of the country's territory compared to 25 percent at the time the Russian military became involved at the end of 2015. Out of 4 de-escalation zones (Homs, Eastern Ghouta, Deraa, and Idlib) created as a result of the Astana roundtable in May 2017, 3 have been returned to Damascus' control with Moscow's physical support. Idlib is nearly the sole opposition stronghold left. As a result of the regime's offensive on Idlib from December 2019 to March 2020, Damascus regained control over significant parts of Idlib and Aleppo. As a result, full control over the strategic M5 highway has been regained by Assad with Russian air support. Meanwhile, as a result of a protocol to the agreement concluded on March 5, 2020, the M4 highway in Idlib is being jointly patrolled by Turkey and Russia. The Turkish-Russian tandem continues to play a significant role in shaping the crisis' trajectory. According to the memorandum signed on 22 October 2019, Turkish-Russian joint patrols continue to take place. However, according to the same agreement, Russia has not guaranteed the withdrawal and disarmament of YPG elements from the Turkish-Syrian border and Manbij and Tel Rifat. Thus, Turkish security concerns are not as obsolete as the conflict of interests between Turkey and Russia.

Funding
This research received no external funding.

Contribution
Writing, methodology, original draft preparation by MCG; conceptualization, resources, writing, validation by CDI; All authors have read and agreed to the published version of the manuscript.

Data Availability Statement
Not applicable.

Disclosure statement
No potential conflict of interest was reported by the authors.