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Updated on 15 November 2019


Section 12:   Communications


In 2018-19, cleavages widen over self-defence reported to the Council under Article 51 (with Table)


During the period from 2001 to the present, there have been more instances of Member States informing the Security Council of actions taken in purported self-defence pursuant to Article 51 of the UN Charter than during the previous 55 years.  In parallel, Member States which disagree either with specific claims to be acting in self-defence, or with general trends in this regard, have become more vocal.  Article 51 reads:


“Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security.  Measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.”


In this millennium, Article 51 has been invoked with respect to actions taken in connection with issues between Liberia and Guinea; the Democratic Republic of the Congo and Rwanda; Israel and Hezbollah; Chad and the Sudan; Armenia and Azerbaijan; Georgia and the Russian Federation; Cambodia and Thailand; the Sudan and South Sudan; and Iran and the United States, as well as the situation in Côte d’Ivoire.[1]


However, during this timeframe, the large majority of letters to the Security Council citing Article 51 have involved either actions taken in response to the Al-Qaida terrorist attacks of 2001, or actions in the context of the complex situations in Syria, Iraq, Libya and Yemen, including the terrorist activities of ISIL/Da’esh. 


An article on this website provides a historical overview of reporting pursuant to Article 51.  Two other articles describe reporting pursuant to Article 51 in 2014-15 and 2016-17.  This article will look at letters invoking self-defence sent to the Council President from 2018 to 2019, as well as concerns raised by other Member States.


From 1 January 2018 to the present, eight letters (and possibly a ninth and tenth) reporting actions taken in self-defence have been sent to the Security Council.  Article 51 was cited in seven of these letters, which were sent by Turkey (four), Iran (two) and Syria (one).  The Iranian and Syrian letters each referred to a specific action taken in self-defence and limited in time, whereas the Turkish letters reported operations undertaken that are open-ended in their duration.


The eighth letter (S/2019/624) during the 2018-2019 timeframe was sent by an American representative.  It reported action taken by the United States “in the inherent right of self-defence”, but did not cite Article 51 or the UN Charter.  The letter, dated 1 August 2019, reported that “on 18 July 2019, the United States took action in the self-defence of United States forces following a threat to a United States Navy vessel by forces of the Islamic Republic of Iran.”  It stated that the American ship “was in international waters conducting a planned inbound transit of the Strait of Hormuz” when Iranian unmanned aerial systems “closed within a threatening range”. 


“In response, and in accordance with the inherent right of self-defence, United States forces aboard the ship took necessary and proportionate defensive military action to ensure the safety of the ship and its crew, resulting in the destruction of one or more unmanned aerial systems.”


It should be noted that the American letter was sent two weeks after the incident it described. 


Turkey’s most recent letter during this time period, dated 9 October 2019 (S/2019/804) is the most controversial, as it justifies “Operation Peace Spring”, launched that date in northeast Syria, as being “in line with the right of self-defence as outlined in Article 51 of the Charter”.  The letter states that the operation’s purpose is “to ensure Turkey’s border security, to neutralize terrorists starting from along the border regions adjacent to Turkish territory and to liberate Syrians from the Tyranny of PKK’s[2] Syrian branch … as well as Deash.”  In addition, the letter refers to the Adana agreement signed with the Syrian government in 1998 and states that it “constitutes a contractual basis for [Turkey] to fight all kinds of terrorism emanating from Syrian territory in its hideouts and in an effective and timely manner.”  Contradicting this interpretation, the Syrian government has categorically rejected the legitimacy of any Turkish operations within its territory.  In fact, it has been reported that after having been promised access to the northeast border area by the Kurdish forces there on 13 October, Syrian troops have been moving to confront the Turkish incursion. 


Turkey's first letter during this time period, sent on 20 January 2018 (S/2018/53), detailed a “military operation” it initiated that same day against “terrorist elements” operating in Syria which, it said, included “Deash and the PKK/KCK Syria affiliate, PYD”.  The letter stated that “The national security of Turkey has been under direct threat from the Syria-based terrorist organizations”.  Specifically, it cited a “recent increase in rocket attacks and harassment fire” directed at Turkish territory which resulted in injuries and deaths.  According to the letter, the operation launched by Turkey on 20 January “will target only terrorists and their hideouts, shelters, emplacements, weapons, vehicles and equipment”.  This measure, it affirmed, “was essential in order to ensure the border security of Turkey and our national security based on our right of self-defence, as defined in Article 51 of the Charter, but also within the context of the responsibility attributed to Members States in the fight against terrorism,” in which connection it cited several Security Council resolutions. 


The representative of Syria has responded in writing to this and earlier Turkish letters invoking Article 51.  In his most recent communication, dated 17 May 2019, he again asserted that “the presence of any foreign military forces in [Syria’s] territory without its express consent constitutes aggression and occupation” and called on Turkey, inter alia, “to withdraw its military forces immediately and unconditionally”.  In an earlier letter, dated 1 February 2018 (S/2018/82), the Syrian representative charged that the Security Council’s failure to put an end to the abuse of Article 51 as a pretext for attacks against Syria by the United States-led coalition had “allowed the Turkish regime to use that same pretext for launching a new attack” against his country.  He contended that Article 51, as well as the International Court of Justice Advisory Opinion on the legal consequences of the construction of a wall in the occupied Palestinian territory, “make clear that the type of attack that gives a State the right of self-defence must come from another State, not from individuals or terrorist organizations.”


The Turkish representative’s other two Article 51 letters during this time period, dated 13 November 2018 (S/2018/1022) and 25 January 2019 (S/2019/81), use the present tense to refer to operations inside Iraq against “terrorist organizations, including PKK, Deash and Al Qaeda.”  He states that against a background of terrorists using Iraqi territory including for “systematic cross-border attacks on Turkey, his country “exercises its inherent right of self-defence, as outlined in Article 51 . . . and takes appropriate measures within the context of the responsibility attributed to it by relevant Security Council resolutions in the fight against terrorism.” 


Ever since Turkey’s first letter, dated 25 April 2017, informing the Security Council of military operations it had launched within the territory of Syria and of Iraq (S/2017/350), the Iraqi government has voiced its protest both at Council meetings[3] and in letters.  Iraq’s consistent message has been that “The bombardment of Iraqi territory by the Republic of Turkey and the presence of its military forces in Iraq under the pretext that Turkey is protecting its internal security . . . violate the principles of the Charter” and international law.[4]


Of the two letters reporting pursuant to Article 51 sent by Iran during this timeframe, one relates to an Iranian military operation in northern Iraq and the other, to an operation in Syria.  In his letter dated 11 September 2018 (S/2018/830), the representative of Iran informed the Security Council that Iranian armed forces, “acting in legitimate self-defence recognized by Article 51 … took limited and measured military action on 8 September 2018, targeting a terrorist group located in northern Iraq”, which he identified as the Democratic Party of Iranian Kurdistan. 


In a letter dated 3 October 2018 (S/2018/891), the Iranian representative wrote of “the brutal terrorist attack that took place in the city of Ahvaz on 22 September 2018.  He then reported that the Iranian armed forces, “acting in legitimate self-defence recognized by Article 51 … took limited and measured military action on 1 October 2018 in Syria, targeting terrorist elements that are also linked to the terrorist act in Ahvaz.”


In his sole reporting under Article 51, the representative of Syria sent a letter dated 20 February 2018 (S/2018/141) stating that on 10 February, Israeli warplanes penetrated Syrian airspace “and struck a number of sites in the central and southern parts of the country.”  He stated that “in view of the above”, Syria “exercised its inherent and legitimate right to defend its people and sovereignty” in accordance with Article 51 and its air defences “responded to enemy F-16 aircraft, hitting several and bringing down one.”

The ninth and tenth letters possibly reporting action taken in self-defence during this timeframe were sent to the Security Council by Israel.  The first of these letters, dated 27 August 2019 (S/2019/688), states that on 24 August, the Israel Defense Forces (IDF) “acted in Syria in response to an imminent, large-scale terror attack by multiple killer drones targeting northern Israel.”  The letter adds that the IDF “neutralized the threat of launching the armed drones from the [Iranian Islamic Revolutionary Guard Corps] Quds Force and Shiite militia site in Aqrabeh, south-west of Damascus” and that the Israeli action was “successful in preventing the attack.”  What is notable about the letter is that not only does it omit citing either Article 51 or the Charter, but it also avoids explicit mention of “self-defence”.  Rather, it states only that “Israel has the full right and obligation to protect its citizens and its national security interests.”  Nonetheless, should the nature of the letter be seen as falling within the reporting requirement established by Article 51, this would be the first reporting by Israel since 2006.

The other letter sent by Israel in 2019, dated 12 November (S/2019/874), informs the Security Council that on the same day, Israel Defense Forces conducted an operation in "defensive response" against the Islamic Jihad's Baha Abu al-Ata in relation to his "planning additional attacks targeting southern Israel in the near future."  As in his previous letter, the Israeli representative omits an explicit reference to Article 51 and also does not use the term "self-defence".


During the 2018-19 timeframe, other incidents took place which might have been considered by the States involved as acts of self-defence but which were not reported to the Security Council pursuant to Article 51. 


In addition to Israel’s response to the reportedly imminent drone strike by Iran mentioned above, Israeli actions with respect to previous Iranian activities in Syria and Iraq are other instances which might have been conceived of as taken in self-defence but which have not been reported to the Security Council.  On 22 August 2019, the New York Times published an article on several unattributed recent attacks in Iraq against “weapons storage facilities controlled by Iraqi militias with ties to Iran”.  The article also stated that


“Israel had long maintained a policy of silence and ambiguity about its airstrikes in Syria until January, when its outgoing army chief of staff, Gadi Eisenkot, openly described that campaign in The New York Times.  He said Israel had hit Iranian targets or its proxies in Syria and Lebanon ‘thousands’ of times ‘without claiming responsibility or asking for credit.’”[5]

In the case of the United States-led “Combined Joint Task Force – Operation Inherent Resolve” (CJTF–OIR), which continues to operate against the remnants of ISIL/Da’esh in Iraq and Syria, some participating States apparently take the view that their ongoing actions are covered by the open-ended letters sent after 2014, when the CJTF–OIR was established.  Nonetheless, of the 75 countries listed as “Partners” on the CJTF-OIR website, only eleven have sent letters citing Article 51 which report to the Security Council their engagement in the Task Force, and all of these were sent prior to 2018.[6] 


A third example is India’s airstrike in Pakistan of 26 February 2019.  On 14 February, Jaish-e-Mohammed (JeM) claimed responsibility for a suicide bombing in Pulwama, Jammu and Kashmir which killed over 40 members of India’s Central Reserve Police Force.  When India reported striking a training base in Balakot, Pakistan on 26 February, the Foreign Secretary stated that “Credible intelligence was received that JeM was attempting another suicide terror attack in various parts of the country, and the fidayeen jihadis were being trained for this purpose.  In the face of imminent danger, a preemptive strike became absolutely necessary.”  Several legal commentaries noted at the time that the Indian statement was carefully worded so as not to claim that the action had been taken in self-defence pursuant to Article 51.  Rather, India’s Foreign Secretary qualified it as a “non-military pre-emptive action”.  While probably this was primarily for political reasons, it also meant that India stopped short of invoking Article 51 in responding to an attack by a non-State actor and also of attributing some degree of state responsibility to Pakistan for the Pulwama attack.


During two Security Council meetings in 2018, on 6 February (S/PV.8175) and 17 May 2018 (S/PV.8262), several Member States raised concerns regarding recent invocations of self-defence citing Article 51.  The representatives of Brazil, Mexico and Cyprus, in particular, underscored that Article 51 is an exception to the prohibition in Article 2(4) on the use of force by Member States against other States.  Accordingly, they cautioned against expansive interpretations of Article 51 which would seek to authorize actions in response to armed attacks perpetrated by non-State actors.  In the specific case of Syria, a Russian representative, noting that the United States-led coalition was "not invited by the country's legitimate authorities," characterized the rationale initially given for the coalition's presence in Syria as "awkward references to self-defence against terrorism."


The Brazilian representative stated his specific disagreement with invoking “the criterion of the unwillingness or inability of the territorial State to respond to non-State actors”.  He also stressed that the “conditions for any reinterpretation of Article 51 are strict” and that those “norms cannot be changed by the practice of a few States”.  These same concerns, he pointed out, have been raised by the Non-Aligned Movement and the Community of Latin American and Caribbean States.[7]

In discussions in other fora, some Member States have additionally criticized so-called “anticipatory” or “preemptive” actions by States claiming to be acting in self-defence.  Moreover, some delegations, including Guatemala in 2015, have questioned the legality of letters to the Security Council which cite Article 51 in an “open format” and thus seemingly take the position “that once a communication has been sent any future military action can be justified.”[8]  


As for the actual letters reporting to the Security Council pursuant to Article 51, the Brazilian representative has stressed the responsibility of States to provide “sufficient information regarding the attack based on which self defence is invoked so as to allow for the appraisal of proportionality and necessity”.  In addition, he has noted that States reporting actions attributed to self defence need to do so “immediately”, in conformity with Article 51.[9] 


While highlighting the responsibilities of States reporting pursuant to Article 51, some UN Member States also contend that the Security Council is not adequately responding to these communications.  Representatives of Argentina, Brazil and Mexico have expressed concern over the lack of transparency in this regard.[10]   The Mexican representative stated that his delegation in fact did not know “whether the Council, after receiving such a letter, beyond acting as a filing office, holds some formal or informal debate to study and consider its content.”[11] 


Given the interest of all UN Member States in such communications, the Brazilian representative has suggested that “a special section dedicated to listing all communications received under Article 51 be created on the Council’s website”.  This proposal has been noted as well in the Report of the Special Committee on the Charter of the United Nations and on the Strengthening of the Role of the Organization of the General Assembly.[12]  The successive Supplements of the Repertoire of the Practice of the Security Council, drafted by the Secretariat, contain lists of all communications to the Security Council which cite Article 51.  However, only the Council itself can determine in which instances such communications constitute reporting pursuant to Article 51.

Also in the Assembly's Special Committee, the representative of Mexico has signaled his intention to present a non-paper regarding the interpretation and application of Article 51, in conjunction with Article 2 (4).  He has stressed that this document would not be political, but rather “technical and legal” and would address issues of transparency and the practical operation of Article 51.  Committee members, however, are reportedly divided as to whether or not that body would be a competent forum to address such issues.[13]

In light of the widening range of precipitating events cited as reasons for taking action in self-defense, the varying nature and duration of the actions taken in response, differences in the timing and thoroughness of reporting to the Council, and the absence of reporting in instances where it might apply, today’s practice regarding reporting pursuant to Article 51 is marked by extraordinary diversity. 


Such variable practice with respect to Article 51 has undoubtedly been compounded by the fact that the Security Council itself has largely avoided making a determination as to whether a specific action reported to it in fact qualifies as “self-defence”.[14]   While Article 51 does not establish an explicit obligation for the Council to do so, two of the Article’s clauses suggest that the Council would want to monitor the circumstances around reported self-defence, as it is stated that the inherent right to act in self-defence shall not be impaired “until the Security Council has taken measures necessary to maintain international peace and security” and also that the reporting of action taken in self-defence “shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.”  Seemingly it might initially have been conceived that this would involve the Council in considering whether or not it should determine that the situation brought to its attention constituted a “threat to the peace, breach of the peace, or act of aggression” pursuant to Article 39.


In any event, the Security Council has adopted no specific practice for reviewing each instance of reporting pursuant to Article 51, let alone evaluating its legitimacy.  It has usually only been when the Council is seized of a matter in an ongoing way that it has sometimes considered actions taken by a State in purported self-defence, but even in such cases this has normally been without reference to a specific communication.  Thus, having gone so many decades without an established practice for letters sent pursuant to Article 51, it would seem nearly impossible for the Council to muster the necessary unity to initiate one at this late date.


Accordingly, although criticisms are likely to heighten, it is probable that individual Member States will continue to “self-define” permissible self-defence for the foreseeable future, without direct input from the Security Council.  In their 1946 commentary on the Charter, the authors Goodrich and Hambro anticipated such a situation: 

“It becomes clear, then, that whether or not this Article [51] opens the way for wholly independent and autonomous action by Members of groups of Members, without effective control by the [Security Council], will depend in practice upon the good faith shown by Members of the Organization and their ability to cooperate effectively.”[15]

(This update supplements page 438 of the book.)                               



[1] See table to the right for a full list. 

[2] Kurdistan Workers’ Party.

[3] See, for example, S/PV.8462 of 13 February 2019.

[4] Letter dated 7 January 2019 (S/2019/16).

[5] Relating to another incident, on 21 March 2018, the Israeli military for the first confirmed that on 6 September 2007, Israeli fighter jets carried out airstrikes against what was believed to be a nuclear reactor in the Deir el-Zour region of Syria. 

[6] The CJTF–OIR website no longer distinguishes those countries which are primarily involved in capacity-building, training, and other non-combat military support.  More details on letters sent in this connection can be found in articles on this website covering 2014-15 and 2016-17.

[7] S/PV.8262.

[8] S/PV.7539.

[9] S/PV.8175.

[10] S/PV. 8262 and 7539.

[11] The Mexican representative additionally queried whether communications transmitted pursuant to Article 51 are published or referenced in the UN Journal.  In fact, since 1958, when the first such letter was transmitted to the Security Council, each has been given a document symbol and published as an official Security Council document, which is then listed in the Journal.  However, as is the case with all other official documents, the Journal provides no description.

[12] A/73/33, page 6.

[13]  A/AC.182/2019/L.10.

[14] Only in the case of the 1981 destruction by Israel of the Osirak atomic reactor in Iraq has the Council adopted a resolution explicitly rejecting such a claim.  At a Council meeting held on 12 June 1981, the Israeli representative claimed in destroying the reactor, his country “was exercising its inherent right of self-defence.  The Council thereafter unanimously adopted resolution 487 (1981) which condemned the Israeli attack as a “clear violation of the Charter”, thus evidently rejecting Israel’s claim that its military action had been undertaken in self-defence pursuant to Article 51 (S/PV.2280).

[15] Leland M. Goodrich and Edvard Hambro, Charter of the United Nations:  Commentary and documents, Boston, World Peace Foundation, 1946, p. 181.



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