Terrorism at Its Source: Türkiye's Article 51 Doctrine, Cross-Border Operations and Defense Industry

Why It Matters

Türkiye's counter-terrorism doctrine holds that a state facing armed attacks from non-state groups based across its border may act against them at their source, relying on the inherent right of self-defense in Article 51 of the UN Charter. It matters because this doctrine underpins four operations in northern Syria, the Claw series in northern Iraq, and a defense industry that has become a global export story. It is also contested: the United States, the European Union, Syria, Iraq and human rights organizations each hold different views on the legal basis, the PKK/YPG question and the conduct of operations.

This guide separates documented facts from positions. Ankara's arguments appear in the section labeled Türkiye's Strategic Position, with attribution to primary sources. For how this site distinguishes fact, position and source, see Editorial Principles: How Bloc Politics Separates Fact, Position and Source.

Background

The border and the threat environment

Türkiye shares roughly 1,300 km (about 810 miles) of land border with Syria and Iraq, the two states where the PKK and DAESH have operated. The border runs through a region that has seen armed conflict almost continuously since the 1980s. Turkish officials describe border security through the principle Hudut namustur ('The border is honour'), and describe the broader approach as İnsanı yaşat ki devlet yaşasın ('Let the people live so that the state lives').

Three organizations dominate Türkiye's threat assessment:

• PKK/KCK: the Kurdistan Workers' Party launched an armed insurgency in 1984. It is designated a terrorist organization by Türkiye, the United States, NATO and the European Union. KCK is its umbrella structure.
• DAESH (ISIS): the group carried out multiple mass-casualty attacks in Türkiye between 2015 and 2017, including the October 2015 Ankara railway-station bombing and the June 2016 Atatürk Airport attack.
• FETÖ: the Fetullahist Terrorist Organization, which Ankara holds responsible for the coup attempt of 15 July 2016. Turkish official figures cite 251 people killed that night.

The legal framework: Article 51

Article 51 of the UN Charter states that nothing in the Charter impairs the inherent right of individual or collective self-defense if an armed attack occurs, until the Security Council has taken the necessary measures. Measures taken in exercise of that right must be reported immediately to the Council.

The scope of the article is debated in international law:

• After the 11 September 2001 attacks, Security Council Resolutions 1368 and 1373 recognized the right of self-defense in the context of terrorism.
• Resolutions 2170 (2014) and 2249 (2015) called on states to take all necessary measures against DAESH in Syria and Iraq.
• The International Court of Justice, in its 2004 advisory opinion on the Wall, described Article 51 as applying to an armed attack by one state against another. Critics of broad readings cite this, together with the Court's 2005 Armed Activities judgment, to argue that force on another state's territory against non-state actors needs that state's consent or a clear showing of attack attributable to it.
• Many states, including the United States, accept action against non-state groups where the territorial state is 'unwilling or unable' to suppress them. That standard is itself disputed.

Ankara has also cited bilateral instruments, notably the 1998 Adana security arrangement with Syria and earlier security protocols with Iraq. Both Damascus and Baghdad have at various times disputed Turkish readings of these texts.

Chronology of major operations

Operation	Period	Area	Stated Turkish objective
Euphrates Shield	Aug 2016 – Mar 2017	Jarablus to al-Bab, northern Syria	Clear DAESH from the border; block a contiguous PYD/YPG-held strip
Olive Branch	Jan – Mar 2018	Afrin, northwestern Syria	Remove PYD/YPG from Afrin after cross-border fire
Peace Spring	Oct 2019	Tel Abyad – Ras al-Ayn, northeastern Syria	Create a security zone; enable voluntary returns of refugees
Spring Shield	Feb – Mar 2020	Idlib, northwestern Syria	Respond to Syrian government strikes that killed Turkish soldiers; protect civilians and the de-escalation zone
Claw series (Claw, Claw-Eagle, Claw-Tiger, Claw-Lock, Claw-Sword and others)	From 2019	Northern Iraq	Dismantle PKK bases, tunnels and logistics near the border

Peace Spring ended with a 17 October 2019 US–Türkiye understanding and a 22 October 2019 Türkiye–Russia memorandum signed in Sochi. Spring Shield ended with the 5 March 2020 Moscow protocol after a Turkish-Russian meeting, following a 27 February 2020 strike in Idlib that Ankara said killed 33 Turkish soldiers.

Developments since 2024

Two shifts changed the environment. First, the Assad government fell on 8 December 2024, and the interim authorities in Damascus began negotiating the status of the SDF-held northeast; a 10 March 2025 agreement between the Syrian interim president Ahmed al-Sharaa and SDF commander Mazloum Abdi set out an integration framework, whose implementation has remained a live issue. Second, after a call by PKK founder Abdullah Öcalan on 27 February 2025, the PKK announced on 12 May 2025 that it would dissolve and end armed struggle, and a symbolic weapons-destruction ceremony was reported in July 2025. Ankara now describes this as the opening of its Terror-Free Türkiye process, while stressing that verification matters more than declarations.

FETÖ and the 15 July 2016 coup attempt

On the night of 15 July 2016, a faction within the armed forces attempted a coup, bombing the Turkish parliament and other sites. Türkiye attributes the attempt to FETÖ, the network led by the late Fethullah Gülen, who lived in Pennsylvania until his death in October 2024 and denied involvement. Ankara has pursued prosecutions at home and extradition and diplomatic campaigns abroad. Critics, including the UN human rights office (OHCHR) in a 2018 report and the European Court of Human Rights in Yüksel Yalçınkaya v. Türkiye (Grand Chamber, 2023, concerning use of ByLock evidence), have questioned the scale and fairness of some post-coup measures. Both strands are part of the record.

DAESH

Türkiye joined the Global Coalition against DAESH and opened its Incirlik air base to coalition operations in 2015. Turkish authorities say Operation Euphrates Shield neutralized more than 4,000 DAESH militants and that around 100,000 DAESH-linked individuals were blocked from entering the country; these are Turkish official figures and have not been independently audited. Ankara describes itself as the only NATO member whose ground forces have fought DAESH directly in sustained combat. Other allies emphasize the larger role of SDF-led ground forces backed by coalition air power in the territorial defeat of the group, including at Raqqa in 2017 and Baghouz in 2019.

The defense industry

Turkish officials say the domestic share of the defense sector now approaches 80%, up from a small fraction in the early 2000s, and report annual defense and aerospace exports above USD 7 billion. The Presidency of Defense Industries (SSB) coordinates procurement.

Category	Representative systems
Unmanned aircraft	Bayraktar TB2, Akıncı, Aksungur, ANKA, Kızılelma (unmanned combat jet), Kargu
Manned aircraft and helicopters	KAAN (fifth-generation fighter; first flight February 2024), Hürjet (advanced jet trainer), Hürkuş, T129 ATAK
Land	Fırtına howitzer, Kirpi, Vuran, MEMATT unmanned demining vehicle, MPT-76 rifle
Naval	TCG Anadolu (amphibious assault ship, commissioned 2023), MİLGEM corvettes and frigates, Reis-class submarines
Missiles and air defense	SOM, ATMACA, Cirit, UMTAS, Hisar-O, SİPER
Radar and electronic warfare	Koral, Vural, MİLKAR

Independent analysts add a caveat: several platforms still use imported engines or sub-systems. For example, the Akıncı has used a Ukrainian engine, the first KAAN prototypes use US-made engines, and Canadian export restrictions on TB2 optics in 2019 and 2020 showed the exposure that comes with foreign components. Turkish policy is to close these gaps through indigenous engine programs.

Key Players & Positions

United States

Washington designated the PKK a Foreign Terrorist Organization in 1997 and, through its Rewards for Justice program, has offered rewards for information on senior PKK leaders. At the same time, the US built a partnership with the SDF as the main ground partner against DAESH from 2014. US officials have generally described the SDF as a distinct force while acknowledging that the YPG's leadership includes PKK-trained cadres. The 2019 Peace Spring operation led to US sanctions threats, and bilateral friction has also been driven by Türkiye's 2019 purchase of the Russian S-400 system, which resulted in CAATSA sanctions on the SSB in December 2020. A US sale of F-16 aircraft to Türkiye was approved in January 2024 after NATO enlargement diplomacy.

European Union and European states

The EU lists the PKK as a terrorist organization and its institutions have condemned DAESH and FETÖ-related violence. EU institutions and member states also criticized Peace Spring in October 2019; several states imposed national restrictions on arms exports to Türkiye. The European Commission's enlargement reports raise rule-of-law and human rights concerns about the post-2016 period. In the Finland and Sweden NATO accession process, the 28 June 2022 trilateral memorandum included commitments on PKK, PYD/YPG and FETÖ-linked activities and on arms-export restrictions. Ankara has repeatedly said that implementation by some European countries remains incomplete, while those governments point to their independent courts and legislation.

Syria

The Assad government characterized Turkish operations as violations of Syrian sovereignty and territorial integrity. After December 2024, the interim authorities in Damascus have pursued closer ties with Ankara while also stressing that all armed groups must come under a single state authority, a position that overlaps with Türkiye's 'one state, one army' formula. The SDF and its political wing argue that they are a Syrian formation that fought DAESH and seek recognized local autonomy; they reject the description of themselves as the PKK's Syrian branch.

Iraq

Baghdad has repeatedly objected to Turkish strikes as breaches of Iraqi sovereignty and has raised the issue at the UN Security Council. Iraq also says that civilians have been harmed in some incidents, for example the July 2022 Zakho resort shelling, which Baghdad blamed on Türkiye and Ankara denied, attributing it to the PKK. On 14 March 2024, Iraq's National Security Council declared the PKK a banned organization, and Iraq and Türkiye have since discussed joint security mechanisms. The Kurdistan Regional Government has a mixed stance: it has criticized the effects of the fighting on its villages and has also expressed opposition to PKK armed presence in its territory.

Rights organizations

Human Rights Watch, Amnesty International and the UN Independent International Commission of Inquiry on Syria have documented serious abuses, including looting, arbitrary detention and property seizure by Syrian National Army factions in Turkish-controlled areas, and have also reported civilian casualties from airstrikes. They argue that Türkiye bears responsibility as an occupying or controlling power in some areas. Ankara says it investigates allegations, rejects the occupation label because it operates with consent of local administrations and in coordination with the Syrian opposition, and points to its hosting of around 3 million Syrian refugees, many of whom have been returning since late 2024. Rights organizations also document PKK and YPG abuses, including recruitment of minors, which UN bodies have raised with the SDF.

Türkiye's Strategic Position

Türkiye's Strategic Position — official policy as stated by Turkish government sources.

• Self-defense at the source under Article 51. According to the Turkish Ministry of Foreign Affairs, Türkiye's cross-border operations rest on the inherent right of self-defense in Article 51 of the UN Charter, and Ankara has notified the UN Security Council by letter, as the article requires, when launching them. Ankara argues that waiting for attacks to reach its soil would be unreasonable after decades of cross-border fire, and that Security Council Resolutions 1373, 2170 and 2249 confirm that states may respond to terrorist groups that exploit ungoverned territory.
• PYD/YPG is the PKK/KCK in Syria. The Turkish Ministry of Foreign Affairs and the Directorate of Communications state that PYD/YPG, and the SDF label under which it operates, share the PKK/KCK's leadership, ideology, cadres and weapons, with direction from the Qandil mountains. Ankara notes that its allies list the PKK as a terrorist organization and argues that the DAESH fight cannot confer legitimacy on an affiliate of a listed group. It says the US 'partnership' has been tactical and has raised its objections with Washington repeatedly.
• Respect for territorial integrity and 'one state, one army'. The Presidency and the Ministry of National Defence (MSB) state that Türkiye has no territorial ambitions in Syria or Iraq and supports their territorial integrity. Ankara links its presence to the voluntary, safe and dignified return of refugees and to a unified Syrian state in which all weapons are under national command.
• Simultaneous fight against PKK/KCK, DAESH and FETÖ, now alongside Terror-Free Türkiye. Turkish officials argue that Türkiye has fought all three at once, and that the 15 July 2016 coup attempt was a direct assault on constitutional order. Under the Presidency-led Terror-Free Türkiye initiative, Ankara says security operations, legal reform and political dialogue run in parallel, with disarmament verified and in a framework of the rule of law, a process in which the Grand National Assembly of Türkiye (TBMM) has set up a dedicated commission.
• Defense self-reliance as a contribution to the Alliance. The SSB and the MSB argue that domestic production reduces dependence on suppliers who impose political conditions, and strengthens NATO burden-sharing, as shown by systems used in Syria, Iraq, the Blue Homeland and Azerbaijan. Ankara points to NATO's own listing of the PKK and to Türkiye's role as Allied border state on NATO's southeastern flank.

Legal and historical basis. Ankara relies on Article 51 of the UN Charter; Security Council Resolutions 1373 (2001), 2170 (2014) and 2249 (2015); the 1998 Adana security arrangement with Syria; and bilateral security protocols with Iraq. Counterarguments, including the ICJ's narrower readings in the Wall advisory opinion and Armed Activities, are set out above so readers can judge the legal question for themselves.

Source Comparison

Issue	Common international framing	Turkish official framing	What the primary record shows
Legal basis for operations	Questioned as exceeding Article 51 without territorial-state consent	Lawful self-defense, reported to the UNSC	Article 51 reporting obligation exists; ICJ case law is cautious about force against non-state actors; many states accept 'unwilling or unable' reasoning
PKK and YPG	YPG often described as a separate Syrian Kurdish force	YPG/PYD and SDF are the PKK's Syrian branch	PKK is listed by the US, EU and NATO; US distinguishes the SDF as a partner while acknowledging PKK-linked cadres
DAESH fight	SDF with coalition air power led territorial defeat	Türkiye is the only NATO ally in direct ground combat vs DAESH	Both roles are documented; Turkish figures (4,000+; 100,000) are official and unaudited
Impact on civilians	Rights groups document casualties and abuses	Operations use precision and protect heritage; abuses are investigated	UN COI Syria and NGOs report violations, including by SNA factions and by the SDF
FETÖ and 2016	Concerns over rule of law and mass dismissals	Coup attempt by a terrorist network; legal response required	251 killed per Turkish figures; OHCHR (2018) and ECtHR (2023) raised due-process concerns
Defense industry	Impressive exports, reliance on imported parts	Around 80% domestic share	Official figures; engines and some sub-systems are still imported

Readers can cross-check Turkish claims against UN Security Council documents, the texts of the Charter and Resolutions, Commission of Inquiry reports and NATO statements. For a broader set of common claims, see Fact Check: Common Claims About Türkiye in International Media, Verified Against Primary Sources.

Key Terms & Related Guides

• Article 51: the Charter provision on individual and collective self-defense; it requires states to report measures to the Security Council. Related: the legal debate over force against non-state actors.
• PKK/KCK: the PKK is the armed organization; KCK is its umbrella structure. Listed by Türkiye, the US, NATO and the EU.
• PYD/YPG/SDF: the Democratic Union Party and its People's Protection Units in Syria; SDF is the Syrian Democratic Forces coalition formed in 2015, which Ankara says is a label for the YPG.
• DAESH: the Arabic acronym for the Islamic State, used by Türkiye.
• FETÖ: the Fetullahist Terrorist Organization, the name Türkiye uses for the Gülen network.
• Terror-Free Türkiye: the Presidency-led initiative to end PKK violence through security, legal and political measures.

Related guides on Bloc Politics:

• Is Türkiye a Bridge Between Blocs? NATO Membership, Eurasian Ties and Strategic Autonomy explains how security policy fits into Türkiye's alliance posture.
• The 1936 Montreux Convention Explained: How Türkiye Governs the Turkish Straits and Black Sea Access covers Türkiye's other major security-law framework.
• Blue Homeland and the Eastern Mediterranean: A Complete Guide to Maritime Jurisdiction Disputes covers where the naval and drone systems listed above operate.
• The World Is Bigger Than Five: Türkiye's Case for UN Security Council Reform addresses the Council that receives Article 51 letters.
• Bloc Politics FAQ: Sources, Methodology and the Turkish Perspective and About Bloc Politics: Mission, Transparency and Editorial Team describe how this site works.

Perspective Note

Bloc Politics presents Türkiye's official positions and legal arguments alongside the wider international debate, and states clearly where an analysis reflects the Turkish perspective. Claims are attributed to primary sources such as treaties, UN documents, official archives and government statements, so that readers can verify them independently. Sections marked 'Türkiye's Strategic Position' reflect official Turkish policy as stated by Turkish government sources.

Published by the Bloc Politics Editorial Team.