On Sunday, fighting between Armenia and Azerbaijan, the worst since 2016, left at least 24 dead and a hundred injured.
The ex-Soviet rivals from the Caucasus " a region between the Black Sea and the Caspian Sea " have been locked in a decades-long dispute over the Nagorno Karabakh region.
Nagorno Karabakh, a mostly mountainous region that spans around 4,400 square kilometres (or the size of the US state of Delaware), lies within Azerbaijan but has been under the control of ethnic Armenian forces backed by Armenia since 1994 at the end of a separatist war.
Armenia itself has never officially recognised the region's independence although it has become its main financial and military backer.
Roots of conflict
In 1921, the Soviet Union merged the predominantly ethnic Armenian territory with Azerbaijan.
As the Soviet Union began to crumble in 1991, it became apparent that Nagorno-Karabakh would come under the direct rule of the Azerbaijan government. Ethnic Armenians were unwilling to accept that.
During the breakup of the Soviet Union in late 1991, the enclave of Nagorno-Karabakh held a referendum boycotted by Azerbaijan where the people chose independence over joining either of the two countries. The situation worsened when the Nagorno-Karabakh Autonomous Oblast, an administrative unit, decided to vote to join Armenia.
This de facto status has not been recognised.
In 1991, after the collapse of the Soviet Union, Armenian separatists, backed by the government in Yerevan, seized the territory. The problem was that the territory was home to a significant Azerbaijani minority, as well as seven adjacent Azerbaijani districts. An ensuing war left 30,000 dead and forced hundreds of thousands from their homes.
During the fighting, in which more than one million fled their homes, the ethnic Azeri population " about 25 percent of the total before the war " fled Karabakh and Armenia while ethnic Armenians fled the rest of Azerbaijan. Neither has been able to return home since the end of the war.
By 1992, the violence had increased and thousands of civilians had been displaced, compelling international bodies to take notice.
The Washington Post estimates that 750,000 Azerbaijanis were driven from their homes in the fighting, the vast majority not from the region but from surrounding provinces seized by the Armenian forces. More than three lakh ethnic Armenians inside Azerbaijan were forcefully displaced as well.
Despite a ceasefire mediated in 1994 by Russia, the United States, and France, peace negotiations struggle to move forward and fighting erupts frequently.
Sunday's clashes " which saw Azerbaijan and Armenian separatists accuse each other of igniting the fighting that left both sides with casualties, including civilians " followed a flare-up along the border in July which claimed the lives of 17 soldiers from both sides.
In April 2016, 110 people were killed in the most serious fighting in years.
Revolts and dynasty
Armenia, a Christian country since the fourth century, has been rocked by political and economic instability since it gained independence from the former USSR.
The country's post-Soviet leadership repressed opposition to its rule, was accused of falsifying ballot results, and was largely beholden to the interests of Russia.
In the spring of 2018, mass street protests brought current Prime Minister Nikol Pashinyan to power. He has since cracked down on corruption and introduced popular judicial reforms.
Muslim-majority Azerbaijan, on the Caspian Sea, has been under the authoritarian grip of a single-family since 1993.
Heydar Aliyev, a former officer of the Soviet security services, the KGB, ruled the country with an iron fist until October 2003. He handed over power to his son, Ilham, weeks before his death.
Like his father, Ilham has quashed all opposition to his rule and in 2017 made his wife, Mehriban, the country's first vice president.
Russia and TurkeyTurkey, with ambitions to be a regional powerbroker in the Caucasus, has thrown its weight behind oil-rich and Turkic-speaking Azerbaijan.
Their alliance is fuelled by a mutual mistrust of Armenia, and Ankara routinely issues strongly-worded statements in support of Baku's ambitions to reclaim Nagorno Karabakh.
Yerevan harbors hostility towards Turkey over the massacres of some 15 lakh Armenians by Turkey under the Ottoman Empire during World War I. More than 30 countries have recognised the killings as genocide, though Ankara fiercely disputes the term.
Russia, which maintains close ties with Armenia, is the major powerbroker in the region. It leads the Collective Security Treaty Organisation military alliance of ex-Soviet countries that includes Armenia.
Yerevan relies on Russian support and military guarantees because its defense budget is overshadowed by Azerbaijan's spending on arms.
Oil and diasporaAzerbaijan has recently begun leveraging oil revenues as part of a bid to overhaul its image in the West.
Baku has invested in massive sponsorship deals including the Euro 2020 football championship, which was postponed because of the coronavirus pandemic.
Baku was due to host matches this year and Azerbaijan has held Formula 1 Grand Prix races since 2016.
Azerbaijan has also tried to pitch itself to European countries as an alternative energy supplier to Russia.
On the international stage, Armenia has a vast and influential diaspora that fled during the Ottoman-era repressions.
Reality TV star Kim Kardashian, the late singer Charles Aznavour, and pop star and actress Cher all trace their roots to Armenia.
Some, like Kardashian, have been outspoken on the issue of the Armenian genocide.
With inputs from AFP