Editors’ Note: This post is the first in a two-part series addressing international legal issues related to the ongoing situation in Nagorno-Karabakh.
On 19 September, Azerbaijan launched an “anti-terror” operation into Nagorno-Karabakh, an enclave in Azerbaijan that Armenia has occupied directly and by proxy since 1994 and in which 120,000 ethnic Armenians live. Azerbaijani forces quickly gained the upper hand. By the next day, a ceasefire had been negotiated with Russian “peacekeepers” acting as the intermediary. Currently, talks are underway between the separatists and Azerbaijan; the Armenian government is not participating.
This post surveys the century-long lineage of the conflict, assesses whether Armenia or Azerbaijan has violated the jus ad bellum prohibition on using force, and examines key international humanitarian law (IHL) issues that the situation implicates. Readers are cautioned that these are highly complex issues that depend on the conflict’s hotly disputed factual tapestry; all of them merit deeper analysis than is possible here. That said, the one unquestionable conclusion is that the situation in Nagorno-Karabakh has now changed dramatically – strategically, operationally, tactically, and legally.
Russia acquired the area that is today Armenia and Azerbaijan in 1813. The two countries declared independence when the Russian empire collapsed during the 1917 revolution. Fighting soon erupted between them over several disputed areas, including Nagorno-Karabakh. By 1920, the Red Army had taken control of both, and they were designated Soviet Socialist Republics (SSR).
Nagorno-Karabakh (“Mountainous Karabakh”) lies in Azerbaijan but is populated primarily by ethnic Armenians. Further complicating the situation is a religious divide, for ethnic Azerbaijanis are Muslim, while ethnic Armenians are Christian. Accordingly, in 1923, Stalin, who was then the Commissar of Nationalities, designated Nagorno-Karabakh as an Autonomous Oblast, an administrative unit enjoying a degree of control over its own affairs within the Azerbaijan SSR.
In 1988, as nationalist emotions swept across the Soviet Union, Nagorno-Karabakh passed a resolution seeking to join the Armenian SSR. A weakening Soviet Union opposed the move as it tried to hold the nation together, but the affair triggered ethnic violence in Nagorno-Karabakh and the surrounding regions. Three years later, in 1991, Armenia and Azerbaijan declared independence as the Soviet Union broke apart. Nagorno-Karabakh did the same that year following a referendum its ethnic Azerbaijanis boycotted. Not even Armenia recognizes the so-called Republic of Artsakh (Nagorno-Karabakh Republic, NKR).
Inter-ethic fighting soon morphed into a brutal international armed conflict between the two new countries over control of Nagorno-Karabakh. Tens of thousands died, and over a million persons were displaced. Armenian forces gained the upper hand and, by 1994, had seized Nagorno-Karabakh and much of southwestern Azerbaijan, including territory that connected the enclave to Armenia.
The UN Security Council observed these developments with great concern. In 1993, it adopted four resolutions affirming the inviolability of borders, demanding an immediate cessation of hostilities, urging the parties to establish a “durable ceasefire,” calling on Armenian forces to withdraw from areas it had occupied, expressing concerns over the displacement of civilians, calling for unimpeded access by humanitarian relief efforts, and expressing support for the work of the Conference for Security and Cooperation in Europe (CSCE, today Organization for Security and Cooperation in Europe or OSCE) and its “Minsk Group.” The Minsk Group was, and remains, tasked with conflict resolution and obtaining a permanent agreement on the cessation of hostilities.
Despite the CSCE’s efforts, it was Russia that brought the parties to the table. In 1994, Armenia and Azerbaijan signed the Russian-brokered Bishkek Protocol, a ceasefire agreement that put in place a previously agreed “line of contact” from which troops were withdrawn. As with all ceasefires, the Bishkek Protocol was a temporary arrangement pending the adoption of a “reliable, legally binding agreement” that would permanently end the conflict, establish a mechanism for “ensuring the non-resumption of military and hostile activities,” involve the “withdrawal of troops from occupied territories,” restore communication, and provide for the return of displaced persons to their homes. The envisaged agreement never materialized.
Futile attempts to craft an enduring agreement and periodic skirmishes followed. For instance, in 2016, intense fighting broke out when Azerbaijan tested the strength of the Armenian and separatist forces, which had been considered militarily superior. The four-day war killed scores and wounded hundreds before a Russia-brokered ceasefire ended hostilities.
Hostilities resumed in 2020, with Azerbaijani units crossing the line of contact and engaging Armenian and the NKR Defense Army forces in the heaviest fighting since 1994. By this time, Azerbaijan had the edge militarily. It swiftly broke through Armenian defenses and took back seven districts and one-third of Nagorno-Karabakh. After 44 days of fighting and the loss of 6,500 lives, Russia, which has a defense treaty with Armenia and good relations with Azerbaijan, negotiated yet another ceasefire. That agreement froze the contact line and recognized the transfer of control over the territory that Azerbaijan had taken back.
Nagorno-Karabakh was now completely cut off from Armenia. Therefore, to provide the population with food, fuel, medical supplies, and other goods, the ceasefire agreement allowed Armenia to use a five kilometer-wide corridor through Azerbaijan’s territory (Lachin corridor), which 1,960 Russian peacekeepers would secure.
In December 2022, Azerbaijani environmental activists, believed to be backed by the country’s authorities, began blocking the Lachin corridor, ostensibly in protest against Armenia’s “pillaging of natural resources” in Nagorno-Karabakh. This cut off the delivery of essential supplies, creating a humanitarian crisis. In April 2023, Azerbaijani authorities also established an official checkpoint along the Lachin corridor, claiming it was meant to prevent weapons smuggling. The move further impeded the delivery of relief supplies to Nagorno-Karabakh.
On 19 September 2023, Azerbaijan launched its so-called “anti-terrorist operation” into Nagorno-Karabakh. Officials stated the operation was in response to elections held in the enclave on 9 September and to landmine explosions that killed six Azerbaijanis, including four police officers. Within 24 hours, the Armenian separatists had agreed to a ceasefire that required them to disband, disarm, and surrender control of Nagorno-Karabakh to Azerbaijan. The Armenian military appears not to have been directly involved in the most recent hostilities, likely due in part to the lack of Russian support and its waning influence in the region.
Use of Force
A fundamental issue in the crisis is whether Azerbaijan’s operations violate the UN Charter’s Article 2(4) prohibition on the use of force and its customary international law counterpart. The article provides, in relevant part, that “all Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.” The question in this case is whether force may be used to seize territory.
A State may not use force to acquire the territory of another State, an issue that one of us addressed in an earlier Articles of War post. Armenia’s use of force to secure and maintain control over Nagorno-Karabakh and the surrounding area clearly violated the prohibition, for there is little question that the territory belongs to Azerbaijan. This being so, it has been under Armenian occupation as a matter of law for decades (see below).
Despite this legal reality, there has been broad criticism of Azerbaijan’s operation. The U.S. State Department, for instance, stated, “As we have previously made clear to Azerbaijan, the use of force to resolve disputes is unacceptable and runs counter to efforts to create conditions for a just and dignified peace in the region.” Similarly, the EU High Representative on Developments in Nagorno-Karabakh announced, “The European Union condemns the military operation by Azerbaijan against the Armenian population of Nagorno-Karabakh and deplores the casualties and loss of life caused by this escalation.”
But this begs the question of whether Azerbaijan’s recent actions violated the prohibition. There is consensus that force is permissible in two situations: self-defense and Security Council authorization or mandate under Chapter VII of the UN Charter. There being no Security Council resolution authorizing force, the issue here is self-defense pursuant to the UN Charter’s Article 51: “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.”
That Armenia’s original actions rise to the level of an “armed attack” triggering the right of self-defense is self-evident. Accordingly, since 1993, Azerbaijan has repeatedly cited self-defense to justify its military operations (Harvard PILAC Catalogue). At the 22 September UN Security Council meeting on the current crisis, Azerbaijan’s Foreign Minister offered the same justification, arguing that the military operations “fully aligned with the sovereign right of Azerbaijan to self-defense enshrined in the UN Charter.”
During the earlier round of fighting that erupted in 2020, two schools of thought on the matter emerged. On one side were those who argued that force may not be used to settle territorial disputes, especially, as is the case here, when the territory has been occupied for decades (see here and here). Its advocates point to the Friendly Relations Declaration (General Assembly Resolution 25/2625), which provides that “[E]very State likewise has the duty to refrain from the threat or use of force to violate international lines of demarcation, such as armistice lines, established by or pursuant to an international agreement to which it is a party or which it is otherwise bound to respect” (Principle 1). This is a reasonable view.
However, we are persuaded by the nuanced alternative proffered by Dapo Akande and Antonio Tzanakopoulos. They argue that “an occupation resulting from an armed attack on another state is indeed a continuing armed attack and that the attacked state does not lose its right to self-defence simply because of passage of time.” The two also characterize the Friendly Relations Declaration’s text as reflecting the self-defense condition of “necessity,” which allows force to be used only when non-forcible measures are unlikely to resolve the situation. In their view, “when this armistice line is no longer ‘temporary’, rather it turns into status quo, then at some point it becomes necessary again to use force in self-defence, all other means to repel the armed attack having failed.” We agree as a matter of law, although we also acknowledge the destabilizing aspects of the current operations. And in this case, non-forcible measures, including ceasefires, have not resolved Armenian control over Azerbaijani territory.
As an aside, the Prime Minister of Armenia has claimed his country is “not involved in military operations” in the area, nor does it “have an army in Nagorno Karabakh,” claims disputed by Azerbaijan. Even if true, Armenia is occupying the territory by proxy. However, for the sake of analysis, assume counterfactually that Armenia no longer controls the area, directly or indirectly, and that there are no Armenian troops against which Azerbaijani operations are being conducted. If that were the case, there would be no issue regarding the use of force prohibition. Instead, Azerbaijan would be engaged in a lawful law enforcement operation subject to its domestic laws, international human rights law, and (perhaps) the law of non-international armed conflict, but not the jus ad bellum.
In a succeeding post, we will address jus in bello and other international legal issues related to the Nagorno-Karabakh situation.
Michael N. Schmitt is the G. Norman Lieber Distinguished Scholar at the United States Military Academy at West Point. He is also Professor of Public International Law at the University of Reading and Professor Emeritus and Charles H. Stockton Distinguished Scholar-in-Residence at the United States Naval War College.
Major Kevin S. Coble is an active-duty Army judge advocate and a military professor in the Stockton Center for International Law in Newport, Rhode Island.