Counter-Terrorism at the Source: Article 51, Border Security and Türkiye's Defense Industry

Why It Matters

Türkiye's counter-terrorism doctrine holds that terrorist threats should be neutralized where they originate, before they reach Turkish territory, and that Article 51 of the UN Charter supplies the legal basis. This approach has produced five major cross-border campaign families since 2016, shaped relations with the United States, the European Union, Russia, Syria and Iraq, and driven a large domestic defense industry. Whether the doctrine is read as lawful self-defense or as an over-extension of Article 51 is one of the most contested questions in current security law, and the answer shapes Black Sea, Eastern Mediterranean and Middle East politics alike.

This guide sets out the facts, the legal framework, the positions of the main actors and Ankara's own arguments, clearly separated so readers can judge each on its merits.

Background

The security geography

Türkiye shares a land border of roughly 1,300 km (about 800 miles) with Syria and Iraq combined. Turkish officials describe this frontier with the phrase Hudut namustur ('the border is honour') and with the maxim İnsanı yaşat ki devlet yaşasın ('let the people live so that the state lives').

The PKK began its armed campaign in 1984. The organization is designated a terrorist organization by Türkiye, the United States, NATO and the European Union. Its leadership has long been based in the Qandil mountains of northern Iraq. The PYD and its armed wing YPG emerged in northern Syria during the Syrian civil war; the YPG is the core of the Syrian Democratic Forces (SDF), which partnered with a US-led coalition against DAESH (also called ISIS or ISIL).

The legal framework: Article 51 and related instruments

Article 51 of the UN Charter preserves 'the inherent right of individual or collective self-defence if an armed attack occurs', until the Security Council has taken the necessary measures, and requires states to report measures taken under it to the Council. Three features matter for this debate:

• Reporting: Türkiye has sent notification letters to the Security Council citing Article 51 in connection with its Syria operations, including those of 2016, 2018 and 2019.
• Non-state actors: Security Council Resolutions 1373 (2001) and 2170 and 2178 (2014) recognized terrorism and foreign terrorist fighters as threats to international peace and security. How far Article 51 covers armed attacks by non-state groups operating from another state's territory is debated among states and scholars. The ICJ's 2004 Wall advisory opinion and its 2005 DRC v. Uganda judgment are often cited by critics for a narrower reading.
• 'Unable or unwilling': A number of states, including the United States, accept that self-defense may be exercised against non-state actors when the territorial state is unable or unwilling to suppress the threat. Other states reject this as lacking a basis in the Charter.

Ankara also cites the 1998 Adana Agreement with Syria, under which Damascus undertook not to allow PKK activity on its territory, as part of the bilateral background to its right of action.

Chronology of the operations

Operation	Dates	Area	Stated objective (Turkish officials)
Euphrates Shield	24 Aug 2016 – 29 Mar 2017	Jarablus–Al-Bab, northern Syria	Clear DAESH from the border; prevent a contiguous YPG-held belt
Olive Branch	20 Jan – 24 Mar 2018	Afrin, northwest Syria	Remove PKK/YPG presence threatening Hatay and Kilis
Peace Spring	From 9 Oct 2019	Tel Abyad–Ras al-Ayn, northeast Syria	Create a security zone; enable returns of refugees
Spring Shield	27 Feb – 5 Mar 2020	Idlib, northwest Syria	Respond to attacks that killed Turkish soldiers; halt a new refugee wave
Claw series (Claw, Claw-Eagle, Claw-Tiger, Claw-Lock and later phases)	From 2019	Northern Iraq	Dismantle PKK bases and tunnel networks

After the Spring Shield clashes, Türkiye and Russia agreed a ceasefire in Moscow on 5 March 2020. Peace Spring was followed by US-brokered and then Russia-brokered arrangements (the 22 October 2019 Sochi memorandum) setting out withdrawal of YPG forces from parts of the border area. Air strikes under the Claw-Sword designation followed the 13 November 2022 Istanbul bombing, which Ankara attributed to the PKK/PYD network; the PKK and the SDF leadership denied involvement.

DAESH and the Turkish role

Türkiye listed DAESH as a terrorist organization in 2013 and suffered a series of mass-casualty attacks in 2015–2017. Turkish officials state that Euphrates Shield, including the battle of Al-Bab (December 2016 – February 2017), made Türkiye the only NATO member to fight DAESH in direct ground combat, that more than 4,000 DAESH militants were neutralized in northern Syria, and that some 100,000 individuals with suspected DAESH links were prevented from entering Türkiye. These are Turkish government figures; they have not been independently audited.

FETÖ and 15 July 2016

On 15 July 2016 a faction within the armed forces attempted a coup. More than 250 people were killed, according to Turkish authorities, and parliament was bombed from the air. Türkiye attributes the attempt to the Fetullahist Terrorist Organization (FETÖ), a network led by the US-based cleric Fethullah Gülen, who died in 2024. The group was designated a terrorist organization by Türkiye; most Western governments have not adopted that designation. Ankara's purge of suspected members from the military, judiciary and civil service is the most contested part of the effort, as the next section shows.

The defense-industrial dimension

The operations accelerated Türkiye's push for self-reliance. Turkish officials put domestic content at around 80%, supported by state military factories and shipyards employing about 26,000 specialists, according to Ankara. Representative systems include:

Category	Representative systems
Unmanned aerial vehicles	Bayraktar TB2, Akıncı, Aksungur, ANKA, Serçe, Kargu; Bayraktar Kızılelma (unmanned combat aircraft)
Aircraft and helicopters	KAAN fifth-generation fighter (first flight 21 Feb 2024), Hürjet trainer, Hürkuş, T129 ATAK
Land platforms	Fırtına howitzer, Kirpi and Vuran armored vehicles, MEMATT demining vehicle, MPT-76 rifle
Naval platforms	TCG Anadolu amphibious assault ship (commissioned April 2023), MİLGEM corvettes and frigates, Reis-class submarines
Missiles and air defense	SOM, ATMACA, Cirit, OMTAS, UMTAS, Sungur, HİSAR-O
Radar and electronic warfare	VURAL, KORAL, MİLKAR, MİLKED

For a fuller system-by-system review, see Türkiye's Defense Industry at 80% Domestic Production: From Bayraktar TB2 to KAAN.

Two points of context are often omitted. First, Türkiye was removed from the F-35 program in July 2019 after taking delivery of Russia's S-400 air defense system, and the US imposed CAATSA sanctions on Türkiye's defense procurement agency in December 2020. Ankara cites both as the strategic reason for accelerating indigenous programs. Second, independent analysts note that the 80% figure is Ankara's own, that methodologies differ, and that some critical components, notably engines for early KAAN prototypes, have relied on foreign suppliers while domestic engines are developed. The Reis-class submarines are built with technology transfer under licence from Germany.

From operations to a political process

In late 2024 and early 2025 Türkiye's domestic politics shifted. Nationalist leader Devlet Bahçeli, an ally of President Recep Tayyip Erdoğan, floated a call for the imprisoned PKK founder Abdullah Öcalan to address parliament. On 27 February 2025 Öcalan issued a call for the PKK to disband. The PKK announced its dissolution on 12 May 2025, and a symbolic weapons-destruction ceremony took place in northern Iraq on 11 July 2025. Parliament then set up a commission to examine the legal framework. This is the context of the 'Terror-Free Türkiye' (Terörsüz Türkiye) initiative. In Syria, the fall of the Assad government on 8 December 2024 and the 10 March 2025 agreement between Damascus and the SDF leadership changed the regional picture again.

Key Players & Positions

United States

Washington designated the PKK a foreign terrorist organization in 1997 and continues to list it. It also partnered with the SDF as its principal ground force against DAESH from 2014 onward, and US officials have said they distinguish the SDF operationally from the PKK. In October 2019 the US Congress and administration criticized Peace Spring and imposed short-lived sanctions, which were lifted after a ceasefire arrangement. US officials have repeatedly stated that Türkiye faces a real PKK threat while urging restraint on civilian protection.

European Union and European states

The EU lists the PKK as a terrorist organization, and EU member states have been among the most frequent critics of cross-border operations. After Peace Spring, the EU foreign ministers' conclusions of 14 October 2019 called for an end to the operation and several states, including Germany, France and the Netherlands, restricted arms exports to Türkiye. The Finland–Sweden NATO accession process (Madrid trilateral memorandum of 28 June 2022; Finland joined in 2023 and Sweden in 2024) also centered on Turkish concerns about PKK-linked activity and extraditions.

Russia

Moscow has backed the territorial integrity of Syria while negotiating directly with Ankara on northern Syria, through the Astana format, the 2019 Sochi memorandum and the 2020 Moscow ceasefire. It has criticized specific operations as sovereignty violations while keeping channels open.

Syria and Iraq

Under the former Assad government, Damascus condemned Turkish operations as violations of its sovereignty. Iraq's government has regularly protested Turkish strikes in the north as breaches of sovereignty, while in March 2024 it formally banned the PKK as an organization, and the two states have since expanded security cooperation. The post-Assad Syrian authorities and Ankara have since discussed border security and the integration of armed groups; positions are still evolving.

Kurdish actors, rights organizations and the UN

The SDF and its civilian administration reject the claim that they are the PKK in Syria and say they are a local force that fought DAESH at great cost. Human rights organizations and the UN Commission of Inquiry on Syria have documented abuses, including looting and arbitrary detention, by some Turkish-backed Syrian armed factions in areas such as Afrin, and have raised concerns about civilian casualties and displacement. Ankara says it investigates violations and that its forces protect civilians and heritage sites.

Council of Europe and courts

On FETÖ, the European Court of Human Rights Grand Chamber ruled in Yalçınkaya v. Türkiye (26 September 2023) that convictions based chiefly on use of the ByLock messaging app violated fair-trial and legality guarantees. The Court did not question that the 2016 coup attempt took place. Ankara maintains that the judiciary is addressing individual cases and that the threat from FETÖ is real.

🇹🇷 Official Policy · Primary Sources

Türkiye's Position

The points below summarize official Turkish policy as stated by Turkish government sources. They are Ankara's arguments and are presented as such.

• Terrorism must be countered at its source. According to the Presidency and the Turkish Ministry of National Defense (MSB), Türkiye's 'neutralizing terrorism at its source' doctrine is preventive self-defense: waiting for attacks to reach Turkish cities would put civilians at risk. Ankara argues that cross-border action is therefore a lawful response to threats mounted from northern Iraq and Syria.
• Article 51 is the legal anchor. The Turkish Ministry of Foreign Affairs (MFA) states that operations are carried out under the inherent right of self-defense in Article 51 of the UN Charter and notes that Türkiye has informed the Security Council by letter. Ankara cites Resolutions 1373 (2001), 2170 and 2178 (2014) as confirming that terrorism, including by non-state actors, is a threat to peace, and the 1998 Adana Agreement as a bilateral precedent. It argues that where a territorial state cannot or will not stop an organization attacking Türkiye, defensive action is permitted.
• PKK, PYD and YPG are one organization with different labels. The MFA and Presidency state that PYD/YPG, including under the SDF banner, shares leadership, cadres, ideology and weapons with the PKK/KCK, and that fighting DAESH does not erase that link. Ankara asks partners to apply the same standard to the PKK in Syria as to the PKK in Türkiye, and says that the fight against DAESH is not a licence for a 'terror corridor' on its border.
• Territorial integrity and 'one state, one army' for Syria. Turkish officials state that Türkiye respects the sovereignty and territorial integrity of its neighbours, that operations are temporary in intent, and that they have enabled voluntary returns of Syrians from a country that hosted millions of refugees at its peak. Ankara supports a unified Syrian state with a single national army and has framed Syria's post-2024 transition as an opportunity to close the border-security question.
• Security, law and politics together: Terror-Free Türkiye. The Presidency describes Terror-Free Türkiye as combining decisive security measures with legal, political and social steps under the rule of law, to end a four-decade cycle of violence. Ankara says it continues to fight FETÖ, whose 15 July 2016 attempt it describes as a direct attack on the state, through judicial and institutional means, and that self-reliance in defense production is the strategic guarantee behind all of these goals.

Legal and historical basis in Ankara's reading

The Turkish argument draws on three layers: the text of Article 51 and the Security Council's terrorism resolutions; the Adana Agreement of 1998 and the practice of states responding to cross-border threats; and the historical experience of an insurgency that Ankara says has cost tens of thousands of lives since 1984. For a comparison with another treaty-based security argument, see Why Did Türkiye Intervene in Cyprus in 1974? Article IV of the Treaty of Guarantee. On how Ankara balances security policy and diplomacy more broadly, see The Montreux Convention and the Black Sea and 'The World Is Bigger Than Five'.

Where critics and Ankara part ways

The disagreement is not mainly about whether the PKK is a terrorist organization. The EU and the US agree that it is. It is about three narrower questions:

1. Link: Whether the YPG and SDF are organizationally the same as the PKK, or a distinct local force.
2. Scope of Article 51: Whether sustained operations deep inside another state's territory, particularly occupation of territory, satisfy necessity and proportionality.
3. Conduct: Whether abuses by allied Syrian factions and civilian harm are adequately investigated.

Many analysts note that the post-2024 situation, with a new Syrian government, an agreement between Damascus and the SDF, and the PKK's announced dissolution, could reduce the factual basis of the dispute. Others caution that implementation, guarantees and the fate of fighters remain unsettled.

Source Comparison

The table below compares framing, not facts. Where a claim is attributed, it has not been independently verified by this publication.

Issue	Turkish primary sources (MFA, Presidency, MSB)	Western and international sources (governments, media, NGOs)
Legal basis	Article 51 self-defense; letters to the UN Security Council; Adana Agreement	Article 51 applies only to an armed attack; 'unable or unwilling' doctrine is contested; scale and duration questioned
PKK and YPG	One organization under different names; shared KCK command	PKK is a listed terrorist group; SDF viewed as a distinct partner against DAESH, with differing assessments of links
Operations	Counter-terrorism, border security, refugee returns	Mixed: acknowledgement of Turkish security concerns alongside criticism of displacement, civilian harm and demographic change
DAESH record	Only NATO ally in ground combat; more than 4,000 neutralized	Türkiye is credited with the Al-Bab battle, but earlier border-transit and detention policies are debated; the SDF is credited as the main ground force overall
FETÖ	Terrorist organization behind 15 July 2016	Coup attempt is acknowledged; criticism of mass dismissals and ByLock-based convictions (ECHR, 2023)
Defense industry	About 80% domestic; strategic autonomy	Impressive growth and exports; engine and component dependence; sanctions and export controls shape the supply chain
Terror-Free Türkiye	Security, law and politics combined, led by the Presidency	Cautious welcome; focus on legal guarantees, transparency and implementation

Readers can examine Turkish primary sources on the websites of the Ministry of Foreign Affairs, the Presidency, the Ministry of National Defense and the Directorate of Communications, and compare them with UN documents, European Parliament and Council texts, ECHR judgments and reports of the UN Commission of Inquiry on Syria. For wider claims about Türkiye in the media, see Fact Check: Common Claims About Türkiye in International Media, Tested Against Primary Sources.

Key Terms & Related Guides

• Article 51 (UN Charter): The provision preserving the inherent right of individual and collective self-defense against an armed attack and requiring states to report defensive measures to the Security Council.
• PKK/KCK: The Kurdistan Workers' Party and its umbrella structure, the Kurdistan Communities Union. It is designated a terrorist organization by Türkiye, the United States, NATO and the EU.
• PYD/YPG/SDF: The Democratic Union Party, its People's Protection Units, and the Syrian Democratic Forces they lead. Türkiye treats the PYD/YPG as the PKK's Syrian branch; the US has partnered with the SDF against DAESH.
• DAESH: The Arabic acronym for the group also called ISIS or ISIL, used in Turkish official terminology.
• FETÖ: The Fetullahist Terrorist Organization, the term Türkiye uses for the network it holds responsible for the 15 July 2016 coup attempt.
• Terror-Free Türkiye (Terörsüz Türkiye): The Presidency-led initiative that pairs security operations with legal, political and social measures.
• Hudut namustur: Turkish for 'the border is honour', a slogan of Turkish border policy.

Related guides

• Türkiye's Defense Industry at 80% Domestic Production: From Bayraktar TB2 to KAAN
• Why Did Türkiye Intervene in Cyprus in 1974? Article IV of the Treaty of Guarantee
• The Montreux Convention and the Black Sea
• Blue Homeland and the Eastern Mediterranean: A Complete Guide to Maritime Jurisdiction
• Editorial Principles: How World Agenda Review Separates Fact from Position

For the publication's overall approach, see World Agenda Review: Global Affairs Through Treaties, Archives and Türkiye's Perspective and About World Agenda Review.

Perspective note

World Agenda Review presents global affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Position' reflect official Turkish policy as stated by Turkish government sources. This article reflects World Agenda Review's editorial perspective that presents Türkiye's official positions and legal theses alongside the wider global debate. Claims are attributed to primary sources such as treaties, UN documents, official statements and archival records.

By the World Agenda Review Editorial Team.

Cross-Publication Dossiers & Sister Desk Perspectives

For complementary primary-source analysis across our specialist editorial network, consult:

• The Global Anatomy: Counter-Terrorism at Source: Türkiye's Security Doctrine, UN Charter Article 51 and Cross-Border Operations — Türkiye's counter-terrorism doctrine, Article 51 and cross-border operations explained: Claw, Euphrates Shield, Peace Spring, DAESH, FETÖ and critics' views.
• Borders & Blocs: Counter-Terrorism at the Source: Türkiye's Security Doctrine, Border Operations and Defense Industry — How Türkiye's counter-terrorism doctrine rests on UN Charter Article 51: cross-border operations, PKK/YPG, DAESH, FETÖ, Terror-Free Türkiye, defense industry.
• Regional Balance: Counter-Terrorism at the Source: Türkiye's Border Security Doctrine and Defense Industry — Türkiye's counter-terrorism doctrine explained: Article 51, PKK/YPG, DAESH, FETÖ, cross-border operations, Terror-Free Türkiye and the defense industry.