For more than two decades, a little-noticed conflict in a remote, landlocked sliver of the former Soviet Union has resembled a chronic disease: Every time it appeared to be dormant, a relapse snapped it back to life.
Each spring or summer, troops from Azerbaijan would clash with ethnic Armenians over the breakaway enclave, Nagorno-Karabakh. They would exchange fire, shoot a soldier or two, capture and swap prisoners. Then Azeri, Armenian and separatist officials would exchange derogatory diatribes and accuse each other of breaking a 1994 cease-fire.
But this spring, things were different.
More than a hundred soldiers, volunteers and civilians have been killed this month, mostly during four days of intense fighting that involved artillery, tanks and heavy weapons.
The fighting came close to ending April 5 after a Moscow-brokered cease-fire, officials on both sides said. But the cease-fire didn't hold, and shooting and shelling continue to claim more lives – and raise more political dust.
What are the roots of the conflict?
Azeris, who share linguistic ties with Turkey and a Shiite Muslim creed with Iran, have coexisted with Christian Armenians for hundreds of years in the strategic South Caucasus region. Ottoman sultans, Iranian shahs and Russian czars vied for influence — until 200 years ago, when Russia annexed what are now the neighboring countries of Armenia and Azerbaijan.
A century later, Communist Moscow made Nagorno-Karabakh an autonomous part of the Soviet republic of Azerbaijan, although the majority of the population was ethnic Armenian. The autonomous region's name was not Armenian – "Narogorny" means "mountainous" in Russia, and "Karabakh" is Azeri for "black garden."
Pressure from Moscow kept ethnic tensions at bay, but during the perestroika years of the late 1980s, Nagorno-Karabakh voted to secede from Azerbaijan and join Armenia.
War erupted after the 1991 Soviet collapse, and ethnic Armenian separatists occupied Nagorno-Karabakh and seven adjacent Azeri districts.
Armenian forces backed the separatists, turning the conflict into the first open war between two former Soviet republics. Each side accused the other of atrocities and ethnic cleansing. Armenia said it strove to "reunite Armenian lands," although it never annexed Nagorno-Karabakh.
The 1994 cease-fire halted the worst of the fighting, which had claimed more than 30,000 lives, displaced hundreds of thousands of ethnic Armenians and Azeris — and ended in political stalemate.
The Armenian separatists wound up controlling a speck of land slightly bigger than Rhode Island.
The breakaway government of Nagorno-Karabakh has not been recognized by a single country — not even Armenia, although Armenia's current and previous presidents, Serzh Sargsyan and Robert Kocharyan, once were top officials in the separatist administration.
How do the countries compare?
During and after the war, Armenia seems to have punched well above its weight. Resource-poor and landlocked, with a population of just 3 million, it suffered from brain drain and increasingly depended on remittances from Armenian communities in Russia, France and, especially, the United States.
Neighboring Turkey sealed its border with Armenia and cut off diplomatic ties – the nations have been at odds over the Ottoman-era massacres of Armenians. Instead, Armenia developed ties with another mighty neighbor, Iran.
Armenia could not keep up economically with Azerbaijan, an oil-rich powerhouse of 10 million that enjoyed high oil prices and Turkey's political backing. Western oil companies rushed to develop Azerbaijan's oil and gas fields in the Caspian Sea, and built pipelines to Turkey.
Azerbaijan boosted defense spending so much that, by 2014, it exceeded Armenia's entire government budget. Baku's oil windfall filled the pockets of Russian arms producers – since 2009, President Ilkham Aliyev's government has purchased helicopters, fighter jets, tanks and artillery worth about $4 billion.
"In many ways, Azerbaijan may have felt empowered and dangerously overconfident because of the Russian arms deliveries," said Richard Giragosian, director of the Regional Studies Center in the Armenian capital, Yerevan.
Armenia also bought Russian-made weapons – in smaller amounts, but with a discount, as a member of a Moscow-led security alliance.
Meanwhile, peace talks stalled. They had been mediated by the Organization for Security and Cooperation in Europe and included the so-called Minsk group – Russia, the United States, France and several European nations.
What was once dubbed a "frozen conflict" was heating up.
A flare-up or a long war?
Disillusioned by the mired peace talks, Azerbaijan stepped up military pressure, placing the new tanks, helicopters and artillery along the "line of contact" with Nagorno-Karabakh troops.
"All these years, the Minsk Group was busy trying to make peace between Armenia and Azerbaijan," said Erkin Gadirli, one of the leaders of the Republican Alternative political group in Baku, the Azeri capital. "But things should be put this way – Armenia needs to be forced to withdraw troops from the occupied territory and drop all the territorial claims to Azerbaijan."
On April 2, Azerbaijan accused the separatists of opening fire, retaliated by deploying tanks and aircraft to seize several strategic heights, and threatened to start a full-scale war.
Yerevan claimed that Azeris sucker-punched the separatists, and also issued a threat to recognize Nagorno-Karabakh as an independent state.
Were they bluffing?
"Baku and Yerevan are so decisive partly because they know – somebody will reconcile them," says Moscow-based political analyst Boris Dubnov.
And the heavyweight backers on both sides stepped right in.
Moscow called for an immediate cease-fire and hinted it may deploy peacekeepers. Russian Prime Minister Dmitri Medvedev flew to Yerevan and Baku – where he said that Moscow's sales of arms to both sides keep the region "in balance."
Iran pledged to serve as a mediator, and Turkish President Recep Tayyip Erdogan said he would back Azerbaijan "until the end."
The OSCE condemned the violence, and even Pope Francis called for peace and promised to visit both nations in June.
Armenian and Azeri military officials shook hands in Moscow on April 5, and no one seems interested in a full-scale war.
"Armenia does not need a war anymore. It occupied Karabakh and seven adjacent districts of Azerbaijan and is trying to secure the occupation officially," said Gadirli, adding that "the skirmishes did not morph into a full-scale war because so far, Azerbaijan's army was not tasked to do so."
The conflict may have shown that no major power is able to settle the conflict alone – and that the warring sides and regional players may succeed only when they seek a short-term compromise and a long-term solution in unison.
"Violence could recur at any time, and the latest fighting clearly demonstrates that the combined goodwill and cooperation of Moscow and Washington is no longer sufficient," political analyst Sergey Markedonov wrote in an analysis for the Moscow Carnegie Center, a think tank.
Mirovalev is a special correspondent.