From Euphrates Shield to Spring Shield: How Türkiye Built a Security Belt Along Its Southern Border

Why It Matters

Between 2016 and 2020 Türkiye carried out four named operations in northern Syria: Euphrates Shield (2016–2017), Olive Branch (2018), Peace Spring (2019) and Spring Shield (2020). In parallel it ran the Claw (Pençe) series against PKK bases in northern Iraq. Ankara describes them as a single counter-terrorism effort along roughly 1,300 km (about 810 miles) of Syrian and Iraqi frontier, while the US, the EU, the UN, Damascus and Kurdish-led authorities have each assessed them differently. This guide sets out what happened, what each operation sought, and what each side says in its own words.

Background

The operations grew out of three overlapping problems: the Syrian civil war, the rise of DAESH (also called ISIS), and the expansion of the PYD/YPG along Türkiye's border. Their immediate trigger in each case differed, but the strategic logic Ankara cites is consistent.

The security context before 2016

• PKK background: The PKK has waged an armed campaign against Türkiye since 1984. It is listed as a terrorist organization by Türkiye, the United States, the European Union and, in Turkish official usage, NATO. The KCK is its umbrella structure.
• The 1998 Adana Agreement: Under this Türkiye–Syria security accord, Damascus pledged not to host or support the PKK. Ankara still cites it as part of the legal backdrop.
• Syria after 2011: As Syrian government control receded in the north-east, the PYD and its armed wing, the YPG, took over large areas. Türkiye regards them as the Syrian branch of the PKK/KCK. The US, by contrast, partnered with the YPG-led Syrian Democratic Forces (SDF) against DAESH, capturing Raqqa in 2017 and the last DAESH territory at Baghuz in 2019.
• DAESH attacks in Türkiye: DAESH carried out a series of deadly bombings inside Türkiye in 2015–2016, including an attack on a wedding in Gaziantep days before Euphrates Shield began.

Chronology of the operations

What each phase involved

Euphrates Shield was the first large-scale ground deployment. Turkish forces and Syrian opposition factions, later grouped under the Syrian National Army, took Jarablus on the first day and later moved on al-Bab.

Olive Branch targeted Afrin, a Kurdish-majority district in north-west Syria that was held by the YPG and was not under the SDF's anti-DAESH front. Türkiye argued it was a launchpad for attacks into Hatay and Kilis.

Peace Spring followed a 6 October 2019 US decision to move some forces away from the border area. It ended in two arrangements: a US–Türkiye pause on 17 October and a Türkiye–Russia memorandum on 22 October providing for joint patrols and for YPG withdrawal 30 km from the border outside the operation zone.

Spring Shield was different in kind. It targeted Syrian government forces in Idlib, where Türkiye maintained observation posts under the Astana process, after an airstrike killed Turkish soldiers on 27 February 2020. Russia and Türkiye agreed the 5 March 2020 protocol, including joint patrols on the M4 highway. Moscow denied responsibility for the strike, according to Russian official statements at the time.

The refugee-hosting context

At its peak Türkiye hosted about 3.6 million Syrians under temporary protection, making it the world's largest refugee-hosting country for several consecutive years according to UNHCR. During the winter 2019–2020 Idlib offensive, UN agencies reported close to a million people displaced toward the Turkish border. Turkish officials say this pressure shaped both Peace Spring's safe-zone plan and the Spring Shield decision. Since December 2024 Turkish officials report that hundreds of thousands of Syrians have returned. Read more in the Interstate Journal analysis: Türkiye, Syria and Refugees: Border Security and the Hosting Burden.

Key Players & Positions

Each actor's position has shifted over time, so the descriptions below are attributed to their own public statements and official documents.

• United States: Washington lists the PKK as a Foreign Terrorist Organization and has acknowledged Türkiye's border security concerns. It nevertheless worked with the YPG-led SDF against DAESH and did not extend the PKK listing to the YPG. During Peace Spring the White House imposed sanctions under Executive Order 13894 on 14 October 2019 and lifted them on 23 October after the ceasefire arrangements.
• European Union: The EU lists the PKK as a terrorist organization. In its 14 October 2019 Foreign Affairs Council conclusions it condemned the Peace Spring operation, called for it to end, and said it would not support stabilization funding for a safe zone. Several member states suspended arms exports to Türkiye.
• Syrian government (until December 2024): Damascus described each operation as aggression against Syrian sovereignty and sent letters of protest to the UN. It reached an arrangement with the SDF in October 2019 that brought Syrian army units into border areas such as Manbij and Kobani.
• Syria's transitional authorities (since December 2024): Under President Ahmed al-Sharaa they have cooperated with Ankara. In March 2025 they signed an agreement with the SDF commander Mazloum Abdi on integrating the SDF into state institutions. Implementation has been contested.
• SDF and the Autonomous Administration: They call themselves a Syrian force, deny taking orders from the PKK, and describe the operations as invasions that endangered the anti-DAESH campaign. The SDF has said roughly 11,000 of its fighters died fighting DAESH.
• Russia: Moscow acted as broker, signing the Sochi memorandum (2019) and the Moscow protocol (2020) with Ankara, while backing the Syrian government militarily.
• United Nations: The Secretary-General repeatedly urged restraint and humanitarian access. The UN Independent International Commission of Inquiry on Syria documented violations by multiple parties, including abuses attributed to Turkish-backed factions in Afrin and the Tal Abyad–Ras al-Ayn area. Türkiye rejects allegations against its forces and says it investigates misconduct by affiliated groups.
• Iraq: Baghdad has objected to Turkish military deployments on Iraqi territory as sovereignty violations, while cooperating on security with Ankara. In 2025 its national security authorities moved to formally ban the PKK.

Türkiye's Strategic Doctrine

Türkiye's Strategic Doctrine: what Ankara argues and on what basis

• Self-defense at the source (Article 51): According to Turkish letters to the UN Security Council and Ministry of Foreign Affairs statements, Türkiye acted under its inherent right of self-defense against terrorist threats originating from areas the Syrian state did not control. Ankara adds that Damascus had failed to meet its obligations under the 1998 Adana Agreement. For the notification mechanics, see The Worldlogue's Article 51 analysis.
• 'One state, one army': The Presidency and the Ministry of Foreign Affairs state that Türkiye respects Syria's territorial integrity and has no territorial ambition. Turkish officials argue that armed non-state structures should not remain outside a single state army, and they welcomed the March 2025 integration agreement in principle.
• PYD/YPG as the PKK's Syrian branch: The Ministry of National Defence (MSB) and the Presidency maintain that the PYD/YPG shares leadership, cadres, ideology and weapons with the PKK/KCK. Ankara says the fight against DAESH is not a legal shield for that link. Washington's distinction between the two is the central unresolved disagreement.
• Ground combat against DAESH: Turkish officials state that Euphrates Shield neutralized over 4,000 DAESH militants and that Türkiye is the only NATO member to have fought DAESH directly on the ground in a large-scale operation. Coalition partners describe their own roles differently, as air support, special forces and training alongside local partners. These figures come from Turkish government sources and are not independently verified.
• Humanitarian and return policy: Ankara cites the burden of hosting millions of Syrians and presents the safe zone and voluntary returns as a humanitarian rationale. Critics, including the EU in 2019, questioned whether large-scale return could be voluntary and safe.

The doctrine is also tied to the Terror-Free Türkiye initiative; see What Is the Terror-Free Türkiye Initiative? and the wider defense-industry dimension in Polity Review's Neutralizing Terrorism at Its Source. For the geographic reasoning behind Ankara's posture, see Türkiye's Strategic Meridian.

Source Comparison

The table below shows where framings diverge and where primary documents can be checked.

Some of these questions, such as civilian harm and the legality of presence without consent, depend on facts that are contested and on legal interpretations that differ across states. Our approach to attribution is explained in Editorial Principles. A parallel treatment of the legal debate appears in Gazetteer of Nations' Article 51 of the UN Charter and Türkiye's Cross-Border Operations.

Key Terms & Related Guides

• Article 51: The UN Charter provision that preserves the inherent right of self-defense after an armed attack, subject to reporting to the Security Council.
• PKK/KCK: The Kurdistan Workers' Party and its umbrella structure. The PKK is listed as a terrorist organization by Türkiye, the United States, the EU and, in Turkish official usage, NATO. In 2025 it announced its dissolution.
• PYD/YPG: The Democratic Union Party and its People's Protection Units in Syria, which Ankara treats as the PKK's Syrian branch.
• SDF: The Syrian Democratic Forces, a YPG-led coalition and former US partner against DAESH.
• DAESH: Türkiye's and the Arabic-language term for the group also known as ISIS or ISIL.
• Adana Agreement (1998): The Türkiye–Syria security accord on PKK activity.
• Temporary protection: The Turkish legal status granted to Syrians, distinct from full refugee status under the 1951 Refugee Convention, which Türkiye applies with a geographic limitation.

Related guides:

• Terror-Free Türkiye Initiative Explained
• Türkiye's Strategic Meridian: Grand Strategy from the Mediterranean to the Caucasus
• Regions & Powers: Counter-Terrorism at the Source
• About The Strategic Meridian and FAQ: Sources, Methodology and Perspective

The Strategic Meridian Editorial Team. The Strategic Meridian is an editorial publication that presents analysis from a Türkiye-informed perspective on regional security, maritime law and history. Claims are attributed to primary sources such as treaties, UN documents, official archives and legal texts, and readers are encouraged to consult them directly.