Some observers have called a long-standing dispute between Azerbaijan and Armenia over the region of Nagorno-Karabakh the "frozen conflict".
But fighting that began on Saturday is threatening to destablise the region. At least 30 soldiers from both sides have been killed.
It is the worst violence since a 1994 truce ended a war in which Armenian-backed forces seized the territory from Azerbaijan.
The region of Nagorno-Karabakh is predominantly ethnic Armenian, and placed under Azerbaijan control in 1922 by then Soviet leader, Joseph Stalin.
The Armenian population of this mountainous, landlocked enclave began a push for unification with Armenia.
And as the Soviet Union broke up, a full-scale war began in 1991.
The Armenians took control of Nagorno-Karabakh in 1994 - after the deaths of around 30,000 people.
So, what is the effect of this renewed tension between Armenia and Azerbaijan?
Presenter: Martine Dennis
Daniel Hamilton - Political commentator on eastern European and South Caucasus affairs.
Sergey Strokan - Political commentator at the daily newspaper Kommersant.
Marcus Papadopoulos - Editor of Politics First magazine.
Source: Al Jazeera