Turkish Armed Forces (TAF) carried out ‘Operation Euphrates Shield’ for 216 days from August 2016 to March 2017 in the triangle between Azaz, Jarablus and al-Bab in northern Syria. Thanks to this military operation, Turkey cleared Daesh from the region and halted the risk of the PYD/YPG exercising control of the Syrian side of the shared 911km border by wedging itself between two PYD/YPG controlled areas. In addition, some displaced Syrians voluntarily returned to this region from Turkey, which currently hosts around 3.5 million Syrian refugees — more than any other country.
In line with this previous operation, the TAF launched ‘Operation Olive Branch’ on 20 January 2018 in Afrin, which has been controlled by the YPG. In its letter to the UN Security Council (UN Doc. S/2018/53), Turkey justified this operation on the basis of self-defence and various Security Council resolutions calling on Member States to fight terrorism.
Since the indicated UN Security Council resolutions do not explicitly authorize the cross-border use of force, Turkey’s reliance on it as a justification of its extraterritorial military operation is unacceptable in international law. As far as I see in legal discussions, there is no dispute over this. However, the question of whether Operation Olive Branch can be justified on the basis of self-defence has brought with it some controversy.
According to both Article 51 of the UN Charter and related customary international law, occurrence of an ‘armed attack’ is required for the activation of the inherent right of self-defence. The ICJ identified ‘scale and effects’ as the criteria that ‘distinguish the most grave forms of the use force (those constituting an armed attack) from other less grave forms,’ but has not specified indicators of these criteria (Nicaragua judgment, 1986, para. 191). It should be noted that the scale and effects criteria have nothing to do with numbers. Rather, it is a legal assessment depending on facts and circumstances at hand.
Turkey’s letter indicates that:
‘[t]he 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.’
These trans-border attacks originating from Syria’s Afrin may individually fall below the threshold of an armed attack, but this series of attacks needs to be regarded as cumulative in character. If, as Turkey has asserted, the series of these incidents resulted in deaths and injuries, then it can be treated as a composite armed attack within the meaning of Article 51 of the UN Charter, which entitles the victim State to self-defence. At this point, one should also remember the fact that Turkey has long been targeted by terrorist organizations from the territories of its unstable neighbours, Iraq and Syria. NATO Secretary-General Jens Stoltenberg affirmed this view by stating that:
‘Turkey is the NATO [a]lly 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.’
Some scholars, such as Peters and Talmon, are sceptical that the terrorist attacks occurred prior to the launch of Operation Olive Branch. Their suspicion is understandable, as it is the burden of the victim State to provide substantiating evidence of the factual occurrence of an armed attack (Armed Activities judgment, 2005, para. 146). Turkey should therefore have substantiated the YPG’s attacks and their consequences in its letter to the UN Security Council. Turkey still has the opportunity and burden to convince the international community in this regard.
Supposing that Turkey could not substantiate its allegation, I think the legality of its extraterritorial military operation is worth discussing on the basis of anticipatory self-defence. According to this controversial doctrine, a State is permitted to defend itself not only when an armed attack has already materialized, but also when it is ‘imminent’, as has been accepted by the majority of States and scholars since the Caroline incident. However, the meaning of imminence as a matter of law is the subject of some controversy (for this discussion, see Green, Hakimi and Milanovic). Reisman and Armstrong survey the contemporary State practice and conclude from statements of several States that imminence is interpreted more flexibly in State responses to terrorist organizations. In line with this conclusion, Hakimi indicates that anticipatory self-defence ‘might already be shifting or might soon shift from the restrictive position toward the more permissive one.’
In its letter to the UN Security Council, Turkey indicated that Operation Olive Branch was initiated to respond to the recent increase in the PKK/YPG’s long-standing attacks and to counter terrorist threats from Syria. Turkey’s military actions and legal position in this respect seem to be in line with the practice and legal positions of some States such as Australia, Canada, the UK and the US, which justified their use of force in Syria on the basis of an individual or collective right of self-defence to respond to terrorist threats or imminent armed attacks. Peters rightly expresses her concern that opening the door of self-defence to ‘the threat of terrorism’ may trigger abusive invocations of self-defence. Likewise, it should be kept in mind that the requirement of imminence is more likely to be satisfied with evidence of a perpetrator’s concrete plan to launch an armed attack rather than just the mere capability to launch one in future. However, what Turkey argues here is not only the general threat of terrorism or mere capacity of a non-State actor: Turkey points directly to the propensity of the PKK and its affiliates to launch attacks when conditions are suitable. In other words, Turkey has considered the recent increase in the PKK’s long-standing attacks and concluded that it represents a permanent and active threat of further attacks, both in terms of capacity and intent.
The PKK has caused the loss of more than 40,000 people, including civilians, in its terrorist attacks in Turkey since 1984. States including but not limited to members of the EU, Australia, Canada, the UK, and the US, as well as international organizations such as NATO and the EU, see the PKK as a terrorist organization. A report published by The Henry Jackson Society, a London-based think tank, in 2017 indicates that the PKK and the PYD/YPG ‘are organically integrated components of the same organisation — sharing membership, ideology, and a command structure.’ Iraqi Kurdish leader Masoud Barzani in 2016 indicated that the PYD/YPG and the PKK are ‘exactly one and the same thing.’ Even the former U.S. Secretary of Defence Ashton Carter and the U.S. Central Intelligence Agency have confirmed that they see the PYD/YPG as a Syrian wing of the PKK terrorist group. The aim here is not to put all Kurds in the PKK/PYD/YPG terror basket. On the contrary, the PYD/YPG should not be considered a legitimate representative of the Kurdish population in that region due to its affiliation with the PKK, and should not be a partner in the fight against Daesh. The reason why this terrorist organization operates under different brands is explained by the US Army General Raymond Thomas, the head of Special Operations Command, as following:
‘They formally called themselves the YPG, who the Turks would say equated to the PKK. So we literally played back to them that you’ve got to change your brand. What do you want to call yourself besides the YPG? With about a day’s notice they declared that they were the Syrian Democratic Forces.’
Whatever they name themselves, this kinship seems sufficient to categorize the PYD/YPG as a Syrian wing of the PKK. The YPG has taken advantage of the conditions of the instability in Syria and expanded its control over the areas in northern Syria alongside the Turkish border thanks to extraordinary US military support, repeatedly condemned by Turkey. Under these circumstances, had it not launched this military operation, Turkey may have lost the opportunity to defend its border security effectively. In other words, failure to stop the advance of the YPG along its border today would reasonably be expected to result in the YPG’s larger-scale attacks against Turkey in near future.
Australian Attorney-General, Senator the Hon. George Brandis QC, has expressed the long-held position of his country regarding anticipatory self-defence by stating that:
‘[…] acting in self‑defence does not require a State passively to await attack. That view is shared by the United Kingdom, the United States, and other like‑minded countries.’
That view is also shared by Turkey as it launched Operation Olive Branch to stop the advance of the YPG and its terror corridor in northern Syria before it loses the opportunity to defend itself effectively.
Although there is significant legal uncertainty over the question of whether an armed attack by a non-State actor not attributable to a State suffices to trigger self-defence (for this discussion, see Milanovic’s article), State practice in the wake of 9/11 has started to evolve in the direction of affording States the right of self-defence in response to attacks conducted by non-State actors. This evolution is, in fact, not contrary to the UN Charter, as nothing in the language of Article 51 limits ‘armed attack’ to attacks attributable to a State. Accordingly, as has been embraced by some States, such as Australia, Canada, Germany, Turkey, the UK and the US, when the host State is ‘unable or unwilling’ to prevent its territory being used as a base for launching attacks against the victim State’s territory, the victim State is permitted to exercise its right of self-defence providing that its requirements are met.
The ICJ, however, has not embraced this approach yet (Wall advisory opinion, 2004, para. 139; Armed Activities judgment, 2005, para. 147). In line with the jurisprudence of the ICJ, many scholars, such as Heller and Green, argue that there is no consistent State practice supporting the ‘unable or unwilling’ test in relation to self-defence actions adopted against non-State actors.
The willingness of subjects of international law to apply the right of self-defence against non-State actors can be observed by the recognition of the US right to respond in self-defence against the 9/11 attacks (see Paust’s article). I think, in the face of such recognition by the Security Council, NATO as well as majority of States, international courts and scholars should have been prepared to review their traditional approach. Otherwise, giving this right to one State but not to others would be a double standard, violating the understanding of the equality of States enshrined in Article 2(1) of the UN Charter and undermining the international legal order.
Proportionality and necessity
In accordance with customary international law, the ICJ confirmed that two more criteria, proportionality and necessity, need to be met for a lawful exercise of self-defence (Nicaragua judgment, 1986, paras. 176, 194; Oil Platforms judgment, 2003, paras. 43, 73-74, 76).
The scale, scope, duration and intensity would be determinant factors in an assessment of the proportionality of any self-defence action. Turkey should, therefore, exercise its military operation in accordance with the statements of Turkish officials emphasizing its temporary nature and limited purpose of clearing its border from terrorist organizations.
As to necessity, the US has been warned by Turkey several times in recent years for its increasing military support to the YPG by providing heavy weapons, training its fighters and even planning to create a so-called ‘Border Security Force’. This support has increased the YPG’s military capacity in Afrin, triggering Operation Olive Branch. Given this growing capacity, no less intrusive means remain available to Turkey to defend its national security interests aside from conducting an extraterritorial military operation against the YPG.