Introduction

Since the establishment of the People's Protection Units (YPG) in 2012, Turkey has insisted that the militia should be classified as a branch of the Kurdistan Workers' Party (PKK), which Turkey and the US classify as a terrorist organization. Turkey has since threatened to launch military operations outside the Turkish border to eliminate the group, even though it previously preferred to refer to the elimination of "terrorist movements" without naming them.
After the People's Protection Units took control of Tell Abyadin in the countryside of Raqqa and other areas in that area, Turkey increased its threats and insistence that it would not accept a Kurdish entity on its borders as this might threaten its national security.
On August 24, 2016, Turkey announced the launch of Operation Euphrates Shield that was aimed at blocking the People's Protection Units from reaching Mosul (Kobanî and Afrin). Although the declared objective of Operation  Euphrates Shield was not to stop at Al-Bab city but to reach Manbij and push the People's Protection Units and the Syrian Democratic Forces back from the Western Euphrates, the operation stopped on March 31, 2017(1)  after achieving nearly "half of the planned objective". The Operation Forces took control over an area of 2225 km2 without reaching Manbij as a result of the intervention by the United States and Russia and the transfer by Manbij Military Council (MMC)(2)  of some areas to the Syrian regime in order to create a separation between the areas that are under the control of the People's Protection Units and those under the control of the Turkish Army.
After announcing the suspension of Operation Euphrates Shield, Turkey announced that it was preparing to launch new operations under other names.(3) 
Turkey was not able to reach an agreement with the former US administration concerning Turkey’s participation in the battle of Raqqa, since the administration insisted on relying on the Syrian Democratic Forces, for which the People's Protection Units form the backbone in the battle of Raqqa.
After the start of the Trump administration’s term in Washington, there have been signs of a breakthrough in US-Turkish relations, which worsened dramatically between 2012 and the end of Obama's term. However, this has not yet been reflected in a clear change to previous US strategy.
US-Turkish relations have witnessed negotiations at senior military and security levels. The Director of the US Central Intelligence Agency, Mike Pompeo, along with the US Chair of the Joint Chiefs of Staff, Joseph Dunford, made separate visits to Turkey to discuss contentious issues between the two sides. However, it seems that the negotiations did not succeed in persuading the United States to abandon the Syrian Democratic Forces as a key partner in the war against ISIS in Syria. At the same time, it is not possible to say that the negotiations between the two sides have failed completely since it is clear from statements by the two sides that they have not yet reached a final position, and the discussion is still ongoing.
The Turkish president's discussions in Washington in mid-May are expected to witness Turkish-American agreement on the role of the People's Protection Units in and after the battle of Raqqa and Kurdish plans for self-administration in Syria, and what Turkey claims is the transformation of Kurdish areas in Syria into a human reservoir of support for the PKK, supplying human, political and military resources.

Turkish strikes

On the morning of April 25, the Turkish aircrafts carried out around 26 raids on locations belonging to the People's Protection Units in areas close to the city of Dayrik / Al-Malikiyah in Al-Hasakah Governorate, including the headquarters of the People's Protection Units in Mount Qarachok, and locations belonging to the Sinjar Protection Units (Turkish: Yekîneyên Parastina Şengal: YPŞ)(4)  in the Şengal / Sinjar area in the region of Iraqi Kurdistan.(5)  These strikes caused the deaths of between 20-30 members of the People's Protection Units(6)  and 30-40 members of the Sinjar Protection Units.(7)  In addition, they destroyed several locations and communication towers. The strikes also killed six Peshmerga fighters due to a mistake in the aircraft’s coordinates (according to a Turkish army statement).
This was Turkey's biggest strike against the People's Protection Units and Sinjar Protection Units. The air strikes were followed by minor skirmishes between the two sides on the Turkish-Syrian border in the areas of Afrin and Al-Jazira, which were not severe and did not cause any deaths.

Reactions

All local Kurdish political forces condemned the Turkish strike that targeted the People's Protection Units’ positions, including the Kurdish National Council in Syria and the TEV-DEM Movement for a Democratic Society. However, in the same statement, the Kurdish National Council, which condemned the Turkish strike, demanded that the Democratic Union “conduct a thorough review of its policies, relations and various daily practices that are aimed at suppressing political life in Syrian Kurdistan, and the need to return to a united Kurdish line”. In its statement, the Kurdish National Council held the two sides responsible for this escalation.
As for the TEV-DEM Movement, it did not only condemn the strike but also accused the Kurdistan Democratic Party (PDK) and its leader Masoud Barzani of political collusion with the Turkish government against what they called “the supreme national interests of our people and against their future in all parts of Kurdistan”(8).  The movement also organized demonstrations against the strike in all the towns under the control of the People's Protection Units.
The Kurdistan Regional Government(9)  (KRG) merely condemned the strikes and demanded that the Kurdistan Workers' Party withdraw its armed forces from Shingal / Sinjar. 
Internationally, none of the states allied with the People's Protection Units issued any condemnation. However, the United States expressed its concerns over the Turkish raids on YPG locations.(10)  Omer Celik, the Minister of European Union Affairs(11) , expressed Turkey's objections to such "concerns". Turkish officials claimed that the United States had been informed beforehand of the intended strikes on the areas in question.(12)  
After the strike, the United States relocated some of its armored vehicles to the Syrian-Turkish border in the areas controlled by the People's Protection Units. American troops also passed through the main streets in front of locals, flying the American flag, as an act of reassurance directed at the Kurdish forces. The YPG announced, following the American patrols, that their allies had started to fulfill their responsibilities (towards the People's Protection Units). 
Russia’s stance was close to that of the US, as Moscow made brief statements claiming that the strikes would "increase tensions" and asking the conflicting parties to "show political awareness and focus on the most urgent task today, namely to confront international terrorism by ISIS, Al-Nusra Front and other similar groups”. (13)

On the domestic level, the Syrian regime condemned the strike via an official at the Foreign Ministry, who stated that such attacks "violate international law, the Charter of the United Nations and the principle of good neighborly relations”.(14) 
Turkish authorities apologized and expressed their deep sorrow over the killing of six members of the Peshmerga forces as a result of “confusion regarding coordinates committed by Turkish aircraft. ”(15) 

Implications of the strike

The recent Turkish strike has had many implications at an international level, as well as at the regional level in Syria and Turkey.
Ankara has proved, through these (highly accurate) strikes, its ability to target the YPG in its leading locations in Syria, and that it possesses the necessary information, capabilities and coordinates to do so.
The Turkish entry into Syrian airspace is also significant. In fact, Turkey’s air forces penetrated American-controlled airspace, meaning that Ankara must have coordinated with Washington before the strike, especially as the targets in the Rmelan area are only a few kilometers away from the US base in the region. Thus, the Turkish strike bears a message to the Kurds, the allies of the US, that Washington will not protect them against possible Turkish attacks. Nevertheless, the United States alliance with them in the Al-Jazira region should not be understood as a strategic alliance at the expense of the alliance with Turkey.
The Turkish bombardment came shortly after the failure of US-sponsored negotiations between the Free Syrian Army, represented by the Al-Mu'tasim Brigade, and Syrian Democratic Forces, represented by the Army of Revolutionaries, to hand over towns and villages in the northern countryside of Aleppo (including Tell Rifaat) to the FSA.(16)  However, the negotiations were blocked after the Syrian Democratic Forces refused an offer by the Free Syrian Army, a move that upset the United States. Consequently, the implicit American approval of the strikes can serve two objectives for the United States: 
• First:  to placate its ally, Turkey. The United States is not prepared to lose Turkey as its ally in the Middle East. The current government is not willing to reproduce the tense relations with Turkey that prevailed under the previous administration.
•Second: to put pressure on the Syrian Democratic Forces and the People's Protection Units to show some flexibility during negotiations with  FSA factions backed by Turkey and the United States.
The American stance carried a message to the People's Protection Units that it must change its policies and that it should be aware that Turkey is an indispensable ally to the United States.
The US position, which merely expressed its concerns regarding the strikes, sought to show sympathy towards the People's Protection Units in front of its popular base. However, the People's Protection Units are fully aware that their US allies were aware of the planned bombardment. 
Shortly after the strike, the United States conducted several patrols in Kurdish areas in Syria to monitor the Syrian border with Turkey. It was the first public appearance of US armored vehicles in populated areas. For the first time ever, coalition and US forces allowed local media and inhabitants to photograph their troops and armored vehicles.(17)  
The patrols by American armored vehicles through the area gave a reassuring message to the People's Protection Units and their supporters. It was also an attempt to reduce potential reactions by locals against the YPG and the US presence in the area.
The patrols are essential to convincing Kurdish allies that there is no need for a response to the strikes. Thus, such patrols have themselves become a form of political response to persuade the public. This was reflected by media close to the YPG, which viewed the emergence of these patrols as an American deterrent to any Turkish strikes in the future. 
The strike carried several political messages, most notably that the current situation in Northern Syria is not satisfactory to Turkey, Washington’s ally and a NATO member. All parties, especially the Syrian Democratic Forces (which were still in their honeymoon phase with the Americans under the Obama administration), must make concessions in order to satisfy the Turkish side and avoid a war that could reach the point of ground intervention by the Turkish army. This is not denied by Turkey, which is still signaling its desire to reach Manbij. 

Future scenarios 

Turkey is not concealing its desire not to leave Kurdish areas in Syria under the sole control of the Democratic Union Party, which it views as a branch of the Kurdistan Workers’ Party that does not represent all Syrian Kurds. Turkey wants to involve the Kurdish National Council in managing the Kurdish areas in Syria as a safety valve to prevent the use of these areas as human and economic resources to support what Turkey regards as terrorism. 
Turkey has consistently stressed that it will not allow the establishment of a Kurdish state on its southern borders as this would fuel separatist sentiments among the Kurds in Turkey, which would be a source of concern for Turkish national security.
Turkey is likely to accept the Syrian regime’s reassertion of its control over Kurdish areas rather than see it placed under a special administrative and political arrangement for the Kurds, as that would influence Turkey’s Kurds, which surpass Syrian Kurds in number and geographical reach. However, the Syrian regime’s return will not be accepted by the United States, which plans to stay in the region for a long time. Therefore, Turkey is forced to put pressure in order to put an end to the Democratic Union Party’s control over Kurdish areas, as the least harmful option.
If Turkish efforts do not succeed in persuading Washington to take political measures that achieve Turkish demands, Ankara could continue to consider and implement military options within the boundaries set by the regional balance of power.
The expected scenarios for Turkey’s position can be summarized as follows: 
Turkish Ground Intervention

In this scenario, Turkish forces would intervene in Kurdish areas, with Turkey sending its soldiers into Kurdish regions in Syria to separate and prevent any connection between the Kurdish areas.
Most likely, Turkish ground intervention will not take place in Kobanî and Al-Jazira as these areas have a Kurdish majority, and Turkish troops will not be welcomed by locals, whether supporters of the YPG or others. Therefore, Tell Abyad may be the area favored by Turkey because, by controlling it, Turkey would be able to separate two out of the three districts that make up the Autonomous Administration area. 
The other area most likely to witness Turkish ground intervention is the Western countryside of Afrin, which is adjacent to Syrian opposition-controlled areas.
In addition to ground intervention in Kurdish areas, Turkey may enter Idlib Province. Although Idlib lies outside the Kurdish area of influence, Turkish control over it and perhaps the Western countryside of Aleppo would mean an increase in Turkey’s direct share of control in Syria and thus, its ability to shape the future political solution, including the future of the Kurdish political project. 
 Continuation of aerial strikes 

In this scenario, artillery shelling and air strikes continue in areas under YPG control.The areas of Al-Jazira and Afrin may be the areas most targeted in these intensive operations because they are the heartlands of the YPG and their leaders. The area of  Kobanî contains many American bases that oversee the battles in Raqqa, so it is unlikely that YPG locations in the area would be targeted. 
On the other hand, the YPG are aware that Kurdish areas in Syria are not mountainous, unlike Kurdish areas in Turkey and the Kurdistan region of Iraq. Thus, it is difficult for them to withstand a ground war with the Turkish army without protection from other countries such as the United States and Russia. 
It is also unlikely that the United States would abandon Turkey in return for maintaining the YPG as an alternative ally. The United States could pressure the YPG to accept concessions in return for keeping both allies in the region. These recent strikes (which occurred with the United States’ knowledge) may be a step towards putting pressure on the hardline leaders of the PKK and the YPG to accept a compromise that would satisfy Turkey or risk the YPG’s gains over the past few years as Turkey will insist on confronting what it calls terrorist organizations outside its borders. If no concessions are made by the YPG, the attacks are expected to continue, perhaps at a greater pace and magnitude, with US approval.

Political solutions

In this scenario, Ankara could reach an agreement with Washington so that the American administration would fully abandon its support for the YPG and put pressure to allow the Peshmerga in Rojava to enter the areas of Autonomous Administration to take part in the battle of Raqqa, in order to put an end to the YPG’s monopoly over Kurdish areas in Syria.
Such a solution would be ideal for Turkey and catastrophic for the Kurds, as it would exempt Turkey from significant military losses, even though it would need to pay a high political cost to Washington. Meanwhile, the Democratic Union Party would lose much of what it has built in recent years.
It appears that so far, no agreement with Washington on this issue has yet been established. Such an agreement would involve a complex series of consequences, including on Turkey's relationship with Russia, the future political solution in Syria as a whole, and the war on ISIS in Syria and Iraq, among others.
The visit by the Turkish president to Washington in mid-May is an opportunity for Turkish and American leaders to try to reach an agreement, which could include American promises to stop any Kurdish separatist efforts in Syria and the integration of other Syrian Kurdish parties 
in return for ending Turkish strikes on Autonomous Administration areas.

References