The Turkish Operation in Afrin (Syria) and the Silence of the Lambs

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Operation Olive Branch

On 20th January 2018, the Turkish military started to attack the Kurdish-populated region of Afrin in Syria (“Operation Olive Branch“). With its letter to the Security Council of 22nd January 2018, Turkey justified this action as self-defence in terms of Art. 51 UN Charter. The relevant passage of the letter is: “[T]he threat of terrorism from Syria targeting our borders has not ended. The recent increase in rocket attacks and harassment fire directed at Hatay and Kilis provinces of Turkey from the Afrin region of Syria, which is under the control of the PKK/KCK/PYD/YPG terrorist organization, has resulted in the deaths of many civilians and soldiers and has left many more wounded.” (UN Doc. S/2018/53; emphasis added). Two elements are troublesome in this official Turkish justification.

Non-state armed attacks?

First, it is controversial whether armed attacks of the YPG, a non-state actor, suffice to trigger self-defence in terms of Article 51 UN Charter and underlying customary law. The current law (both Charter-based and treaty-based) is in flux, and still seems to demand some attribution to the state from which the attacks originate. (See for a collection of diverse scholarly opinion, ranging from “restrictivists” to “expansionists”: Anne Peters, Christian Marxsen (eds), “Self-Defence Against Non-State Actors: Impulses from the Max Planck Trialogues on the Law of Peace and War”, Heidelberg Journal of International Law 77 (2017), 1-93; SSRN-version in Max Planck Research Papers 2017-17).

The ICJ case-law has not fully settled the question (see for state-centred statements: ICJ, Oil platforms 2003, paras. 51 and 61; ICJ Wall opinion 2004, para. 139). In Congo v. Uganda the ICJ explicitly refrained from deciding it but implied that − if at all – self-defence was available only against “large scale attacks” of a non-state armed group (ICJ Congo v. Uganda 2005, para. 147).

Interestingly, Turkey in its letter does not even use the term “armed attack” which is required by Article 51, but relies on the “threat of terrorism” and the lack of control by Syria in the Afrin region. This is reminiscent of the German explanation of its military contribution to the collective self-defence of Iraq and France in its 2015 letter to the Security Council: “ISIL has occupied a certain part of Syrian territory over which the Government of the Syrian Arab Republic does not at this time exercise effective control.” (UN Doc. S/2015/946). It may also be recalled that Turkey, in 2015, was one of only four states which relied on the unable or unwilling-doctrine to justify strikes against IS in Syria: “It is apparent that the regime in Syria is neither capable of nor willing to prevent these threats emanating from its territory, which clearly imperil the security of Turkey and the safety of its nationals.” (UN Doc. S/2015/563). To conclude, Turkey seems to imply that either non-state armed attacks by YPG would be sufficient to trigger self-defence directly, or that the lack of Syrian control, its inability to prevent rocket strikes and fire by YPG across the Turkish border, are sufficient to justify Turkey’s use of force which inevitably also affects Syrian territorial integrity and sovereignty.

Threshold of gravity

Second, another condition of lawful self-defence seems not to be fulfilled. In order to qualify as an armed attack in terms of Art. 51 UN Charter, the asserted attacks would have needed to surpass a threshold of gravity in scale and effect.

In the 1986 Nicaragua judgment, the ICJ distinguished between ‘the most grave forms of the use of force’ and ‘other less grave forms’ of the use of force (ICJ, Nicaragua 1986, para. 191).

According to the Court, only the most grave forms constitute an armed attack apt to trigger self-defence. The famous Nicaragua gap has the legal consequence that “less grave forms” of military force − although violative of Art. 2(4) UN Charter − will not be answerable by lawful self-defence. Whether one believes that the Nicaragua gap is helpful to serve the policy objective of preventing escalation of military violence or not, the gap still seems to be good law.

The point where the threshold of an armed attack is reached cannot be measured with mathematical precision. More than 3.000 deaths as in the 9/11 attacks surely count as equivalent to an inter-state military armed attack. And maybe also more than one hundred victims as in the Paris attacks by IS in November 2015 are big enough in scale and effect. In any case, the burden of substantiation and of proof for the alleged armed attack falls on the state which claims self-defence (ICJ, Armed Activities in the Territory of the Congo (2005), para. 146).

According to international news reports, Turkey has not substantiated its allegation. Indeed, there was rocket fire causing some casualties from Afrin across the border, but the strikes seem to have occurred after the Turkish invasion. It therefore seems that (whichever position we espouse in the controversy about non-state authors), an armed attack which would be apt to trigger self-defence, has not been shown. The further requirements of necessity and proportionality also do not seem to be met, especially not in the event of an extension of the operation to further regions, as the Turkish President already announced.

Finally, no other justification of the use of force is in sight, notably no invitation by the Syrian government. To the contrary, Syria protested against the strikes (Hazem Sabbagh, Syria strongly condemns Turkish aggression on Afrin, Syrian Arab News Agency, 20 January 2018). This official statement would have to be taken at face value. Any possible secret arrangement and tacit approval by Syria could not count as valid consent under international law. To conclude − on the basis of the facts known to me − we here face a rather obvious violation of international law.


All the more troublesome is the general silence with which this unlawful act is greeted. The Kurds had, according to newspaper reports, already before the 20th January, when the Turkish offensive became imminent, asked the international community for help (Neue Zürcher Zeitung of 19 January 2018). But not even verbal support came forward. Most states reacted in a non-committal. The United States said they were “very concerned” (USA, Press statement, The Situation in Northwest Syria, Heather Nauert, Department Spokesperson, 21 January 2018).

The German foreign ministry saw the events unfold “with concern” (Press release of 21 January 2018). France, calls on the Turkish authorities to act with restraint” (Press statement, Telephone conversation between Jean-Yves Le Drianand his Turkish counterpart, Mr Mevlüt Çavuşoğlu, 21 January 2018). One state which found clear words is Egypt which considered the Turkish strikes “as a new violation of Syria’s sovereignty”. Neither the UN Security Council (special session of 22 January 2018), nor NATO, nor the OSCE issued an official statement.

The reasons for silence might be manifold: Geostrategic concern for shielding Turkey as the Eastern flank of NATO; reliance on Turkey in the fight against IS; the fear of losing voters with Turkish ethnic background in Western European states; economic interests in arms exportation to Turkey; or the desire to do or to continue doing basically the same as Turkey is doing right now.

Repercussions for the international legal order

But this silence will have repercussions on the international legal order. As mentioned above, neither the UN Security Council nor any other international organisation nor powerful states have clearly denounced the Operation Olive Branch as what it is: As a blatant violation of a fundamental principle of international law. In terms of fairness, this is all the more deplorable as the victims are Kurdish populations which have in the course of the last decades often been left standing in the rain during the armed conflicts of the region.

As a matter of legal policy, we need to concede that the law of self-defence should respond to novel threats and accommodate legitimate security interests of states and their populations. In technical terms, an expansive interpretation of the Article 51 UN Charter, whose wording is open, would be possible. Arguably, what matters from the perspective of the victim is the gravity of the attack and not the attacker. It therefore seems legally possible and also appropriate to modify the traditional attribution criteria (which have been developed for purposes of state responsibility) for identifying an armed attack. This is also the course which state practice seems to take. However, doing away with any link to the state from which the attack originates (in our case Syria) might go too far. First, such a legal construct can hardly well explain the inroads into the territorial sovereignty of an “innocent state”. (I am not saying here that Syria is an innocent state).

Second, and most importantly, opening the door of Art. 51 UN Charter to “the threat of terrorism”, as the Turkish letter has it, carries a huge potential for escalation of violence and for abusive invocations of self-defence. This has been highlighted as recently as 2016 (in cognisance of the Anti IS operations in Iraq and Syria) by the nonaligned states which “reject[ed] actions and measures, the use or threat of use of force in particular by armed forces, which violate the UN Charter and international law (…) under the pretext of combating terrorism” (Final Document of the 17th Summit of Heads of State and Government of the Non-Aligned Movement, 17-18 September 2016, para. 258.34).

The Turkish offensive against Afrin is an example for an aberrant invocation of the inherent right to self-defence. Not protesting against this false legal assertion might in the future fall back on the feet of those states which now fail to denounce the violation of international law and prefer to shut up. It is a silence which will facilitate them falling victim to unlawful trans-border violence at some point, too.

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Selim Ozaycan says

January 30, 2018

One question
How much do you support the idea that the PYD/YPG is the Syrian branch of the PKK with which Turkey has been fighting for more than 40 years and the threshold of gravity in scale and effect has already been met?

Since the affiliation between these armed group (one group with several names and branches) has already been established in articles (See "Dead Men Tell No Lies: Using Killed-in-Action (KIA) Data to Expose the PKK's Regional Shell Game" written by Andrew Self and Jared Ferris or here It should not take long to see the relationship between the PKK and YPG/PYD but in case one wants to it quickly, this article might be of useful (

Alessandra Asteriti says

January 30, 2018

The silence of the wolves more like it.

Mary Ellen O'Connell says

January 30, 2018

Dear Anne,

Very grateful for your swift and expert analysis of this complex case--I concur in your critique of Turkey's letter and deplore attempts to dilute the restrictions on the use of force in self-defense.

But I do consider the silence respecting Turkey's action may have more to do with the fact that Turkey's use of force against the Kurds is welcomed by Syria, just as the anti-ISIS effort. Both are implicit interventions by invitation.

Rather than concluding much respecting the law of self-defense, perhaps we should ask if lack of protest now the equivalent of an invitation?

This is no positive thing but perhaps not as dangerous as the claims in Turkey's letter.

Mary Ellen

Etienne Henry says

February 2, 2018

Dear Professor Peters,

Many thanks for this analysis. Just three minor footnotes, as I have nothing to add on the substance and concur with your conclusion on the illegality of the Turkish invasion:

1. In his statement on 25 January 2018, NATO Secretary-General Jens Stoltenberg, affirmed that ‘Turkey is the NATO Ally which has suffered most from terrorist attacks over many years and Turkey, as all of the countries, have the right to self-defence, but it is important that this is done in a proportionate and measured way, and that is the message I convey every time I discuss this issue with different NATO leaders, including of courser with political leadership in Turkey.’ It could therefore be argued that he endorses Turkey’s arguments except for the application of necessity and proportionality. It seems also that he does not contest the qualification of the YPG as a terrorist group, thus implying that states members of the coalition has been actively supporting a terrorist group. This is regrettable, to say the least. See ‘Joint Press Conference with NATO Secretary General Jens Stoltenberg and the Minister of Defence of Spain, María Dolores de Cospedal García’ (NATO, 25 January 2018) accessed 2 February 2018.

2. The Republic of Cyprus has condemned the Turkish intervention and has qualified it as an act of aggression. See Ministry of Foreign Affairs of the Republic of Cyprus, ‘The Republic of Cyprus Condemns the Illegal Turkish Invasion in Afrin in North-Western Syria. 22 January 2018’ (Ministry of Foreign Affairs of the Republic of Cyprus, 22 January 2018) accessed 27 January 2018.

3. The Islamic Republic of Iran has also issued a perhaps more ambiguous statement. But, in my opinion, the words used by the Ministry’s Spokesman Bahram Qassemi imply a condemnation of the intervention on ground of its unlawfulness. See Ministry of Foreign Affairs - Islamic Republic of Iran, ‘Iran Closely Monitoring Turkey’s Operation in Syria’s Afrin’ (Ministry of Foreign Affairs - Islamic Republic of Iran, 21 January 2018) accessed 27 January 2018.

Kind regards,

Etienne Henry

Etienne Henry says

February 2, 2018

For some reason the link did not follow:

Andrew Filis says

February 2, 2018

A previous commentator refers to the PKK and its affiliates as 'terrorist' whilst there is no contextualisation of the longstanding Kurdish-Turkish conflict which involves the Turkish state, since its inception, oppressing its ethnic and other minorities including the Kurdish people to the point that armed insurrection against the Turkish state became the only meaningful means of resistance.

It is perhaps rich but unsurprising that an apologist of the Turkish state seeks to circumvent the currently crystallised norms of international law concerning the threat or use of force, by arguing that the organic relationship between PKK and YPG is on its own strength sufficient to legitimise transboundary aggression, without first seeking to establish that chronological sequence of events, which would have at the very least required the establishment of facts, including that an armed attack had taken place or was imminent on the part of YPG against Turkish territory.

Those points aside, the whole 'gap' argumentation seems to be a regressive step back to pre-Charter if not way earlier practices and the notions relating to 'state of necessity' and so on rejected for inclusion in the Charter. Ago discusses these ideas at para. 56 onwards of the ‘Addendum to the 8th Report on State Responsibility’. I would agree with the argumentation advanced by Prof. Peters including her concerns in her concluding remarks.

In the event, given the lack of invitation on the part of the Syrian state - let alone its protests - the burden is upon the Turkish state to provide unequivocal evidence that it suffered attacks by a non-state combatant (YPG) whom the Syrian state is unwilling or unable to contain under its due diligence duties owed to the international community with regard to operations on its territory that may pose security threats to other states.

Raj Krishna says

February 3, 2018

A timely and brilliant analysis of this complicated case. Further I too agree with the author wherein she states that the Turkish Operation in Afrin is an example for an aberrant invocation of the inherent right to self-defense. Further immediate corrective measures need to be taken or else it will definitely have repercussions on the international legal order in future.

anne peters says

February 3, 2018

Dear colleagues, Thank you for all useful comments and further points of information that is relevant for the legal assessment of the situation. I would like to draw your attention to a recent paper by Paulina Starski on the legal significance of the silence of states vis-à-vis stretches of self-defence:


Marcus says

February 7, 2018

Without going into the facts (which I don’t know well enough), I found the following sentence puzzling. “Any possible secret arrangement and tacit approval by Syria could not count as valid consent under international law.” I understand why tacit approval is insufficient. But I don’t see why a secret arrangement isn’t sufficient. Only if the arrangement was a treaty would there be an obligation to publish it. And even then if it was kept secret it would not be invalid.
Secrecy is just how states interact. They keep things secret, whether we the spectators like it or not.