As fierce fighting continues between bitter rivals Azerbaijan and Armenia over a breakaway region, fears grow of a regional war that could draw Russia and Turkey.
The two former Soviet republics have reported that dozens of fighters have been killed and hundreds injured since hostilities began on Sunday.
On Tuesday, the two accused each other of shooting directly into each other’s territory beyond the conflict zone, as civilian deaths increased and fighting raged for a third day.
As the violence escalates, NBC News takes a look at the main players and what is behind the recent fighting.
What is Nagorno-Karabakh?
At the heart of the conflict is Nagorno-Karabakh, a mountainous region slightly larger than Rhode Island. It is internationally recognized as part of Azerbaijan, but has been de facto under Armenian control since the early 1990s.
Its attribution to Azerbaijan in Soviet times has been contested by its ethnic Armenian majority. This led to a war after the collapse of the Soviet Union in the early 1990s and Nagorno-Karabakh attempted to declare its independence.
Some 30,000 people have died in the conflict, which also displaced around 1 million people before a ceasefire in 1994. Since then, Nagorno-Karabakh has remained a breakaway region inside Azerbaijan.
There is a local leadership in Nagorno-Karabakh, but the territory, which is home to around 150,000 people, depends on Armenia for its financial support.
The long-standing negotiations brokered by Russia, the United States and France have seen little progress and periodic clashes have taken place at the region’s borders.
Why are we fighting now?
Tensions between the two sides simmered over the summer, turning to deadly clashes in July, which led to hostilities on Sunday.
The July escalation was seen as a setback for Azerbaijan, which reportedly lost a top general in the fighting, said Kevork Oskanian, a political science researcher at the University of Birmingham in the UK.
The clashes on Sunday may have been Azerbaijan’s attempt to save face, Oskanian said.
But as the final fight began this weekend, the roots of the conflict go back centuries.
Armenians consider Nagorno-Karabakh to be the Artsakh province of their former kingdom, Oskanian said.
Meanwhile, the region has central cultural significance for the Azeris, who trace Shusha in modern Nagorno-Karabakh to the 18th century Karabakh Khanate.
While religion is used by both sides for propaganda purposes, both in majority Christian Armenia and predominantly Muslim Azerbaijan, Oskanian said the conflict is almost exclusively about competing secular nationalism on both sides.
“From the Armenian side, you often hear the argument that this is a struggle for life and death, that if their side lost it would mean the annihilation of the Armenians of Karabakh and, perhaps, of Armenia itself, ”he wrote in an email. “On the Azerbaijani side, people are talking about the importance of Karabakh in their perception of what it means to be Azerbaijani.”
What is Turkey’s role?
Turkey has cultural, economic and political ties with Azerbaijan, and the two countries also held large military exercises in July and August.
Strongman President of Turkey Recep Tayyip Erdogan said on Monday that his country will stand alongside “brother Azerbaijan, will have all its resources and all its heart”.
Turkey is trying to bolster its national legitimacy by supporting fellow Azerbaijani Laurence Broers, an associate member of the Russia and Eurasia program of London think tank Chatham House, said in an email.
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“He has recent combat experience in several regional theaters, and he also has a defense industry keen on new markets,” Broers said.
Pashinyan, Prime Minister of Armenia, called on the international community to put an end to any possible interference by Turkey, which, he said, will destabilize the region.
In what could be a major escalation in violence on Tuesday, Armenia alleged that one of its fighter jets was shot down by a Turkish fighter jet, killing the pilot, but Ankara has denied any involvement.
Armenian officials have also accused NATO member Turkey of providing Azerbaijan with Syrian fighters and weapons. Azerbaijan and Turkey deny it.
Turkey has been in a bitter conflict with Armenia over the massacre of 1.5 million ethnic Armenians by the Ottoman Empire, centered in present-day Turkey, at the beginning of the 20th century, which Armenia regards as genocide. The Turkish government has vehemently denied that the killings constitute genocide.
Who else is involved?
Russia remained the most active international actor in the conflict and the main mediator.
Moscow is trying to maintain good relations with both parties to the conflict and to deepen its influence in the region, Oskanian said. The Kremlin also does not want tensions to run out of control and attract outside powers – including Turkey, he added.
While the United States remains one of the mediators in the conflict, Nagorno-Karabakh has not been prioritized by Washington since 2001, Broers said.
The recent outbreak has caught the attention of the United States, however, with Secretary of State Mike Pompeo urging both sides to end the violence on Tuesday.
Reality TV star Kim Kardashian West, who has Armenian roots, also commented, calling for “diplomatic measures to avoid unnecessary escalation and tragedy.” in a series of tweets Sunday, calling on Azerbaijan to “cease all offensive use of force”.
The worst-case scenario is all-out war involving Russia and Turkey, say experts, including Broers.
The conflict could destabilize the South Caucasus region – Armenia, Azerbaijan and Georgia – which serves as a corridor for pipelines transporting oil and gas to world markets.
But Broers and Oskanian said pipelines are not the main consideration, although they could be if the conflict continues.
“Oil and gas pipelines are quite close to the current front line. A few tens of kilometers in fact, ”said Oskanian.
The Associated Press contributed to this report.