Azerbaijan sent troops backed by artillery strikes into Armenian-controlled Nagorno-Karabakh on Tuesday in an attempt to bring the breakaway region to heel by force, raising the threat of a new war with its neighbour Armenia. Read everything you need to know about the conflict below.
Where is Nagorno-Karabakh?
It is a mountainous parcel of land roughly the size of Somerset that has a total population of around 150,000 and is wedged between Armenia and Azerbaijan.
Armenian fighters defeated Azerbaijan in conflicts over control of the region after the collapse of the Soviet Union in 1991 but in a five-week war in 2020, Azerbaijan recaptured most of it.
In the 2020 war, Azerbaijan was backed by Israel and Turkey and used Turkish Bayraktar drones for the first time. They overwhelmed dug-in Armenian positions, shocking Armenia’s military which had thought that they would be impregnable.
The Kremlin stepped in after five weeks in 2020 to impose peace. This left Azerbaijan in control of most of the region except Stepanankert, the biggest town, and its surrounding ethnic Armenian villages.
Why is the region disputed?
These are classic Soviet divide and rule tactics. Nagorno-Karabakh was deemed by Soviet planners to be part of Azerbaijan, even though it was majority populated by ethnic Armenians. Their hilltop churches with conical spires dot the region.
There is no strategic or mineral wealth in the region. It has simply become a point of historical pride and now a blood feud that has killed tens of thousands of people, with both sides committing war crimes.
Analysts have said that Ilham Aliyev, the Azerbaijani president, wants to drive all ethnic Armenians from the region and, emboldened by his military successes three years ago, he intends to finish the job.
Why is the Lachin corridor important?
The Lachin corridor is a road roughly 20 miles long that connects Stepanankert, the only ethnic Armenian town in Nagorno-Karabakh, with Armenia proper.
Azerbaijan has blocked this road since mid-December, first with so-called environmental protesters and more recently with a military checkpoint. The road has become impassable even to aid and food trucks.
Russian peacekeepers watched the protests and the checkpoint being built without intervening.
Ethnic Armenians living in Stepanakert and surrounding villages have told The Telegraph that supplies have been running low. Cut off from Armenia and the Armenian army, and weakened by lack of food and fuel, ethnic Armenians living in Nagorno-Karabakh are vulnerable.
Is it independent from Armenia?
Armenians call the region Artsakh and consider it to be independent of Yerevan with a separate government and defence force. In reality, though, Yerevan backs the government in Stepanakert strongly and provided most of the forces for the failed 2020 war against Azerbaijan.
Nikol Pashinyan, the Armenian prime minister, has said that the main Armenian army will not intervene in a new war with Azerbaijan over Nagorno-Karabakh.
Thousands of Karabakh Armenians now live in Yerevan and also play influential roles in Armenian politics and business.
Does religion play a role in the conflict?
Azerbaijan is a majority Shia Muslim country and Armenia is Orthodox Christian but both sides deny that religion is a driver of the conflict. That said, Azerbaijan has reportedly torn down centuries-old churches in areas that it captured during its successful war in 2020.
What is Putin and Russia’s attitude?
Things have changed since 2020 when Vladimir Putin was able to step in and demand peace after five weeks of war. Then, the Kremlin was still seen as a guarantor of Armenia’s sovereignty, but now its loyalties are far more nuanced.
Angered by Armenia’s shift towards a more pro-West stance and lack of support for its war in Ukraine, the Kremlin may be looking to punish it and humiliate Mr Pashinyan.
It could also see another war in Nagorno-Karabakh as a good way to pull in Western powers and distract them from backing Ukraine.
Could other powers get dragged in?
Yes. Israel and Turkey still back Azerbaijan, as they did in 2020, but with Russia’s support for Armenia evaporating, the EU and the West have increased support for Yerevan.
This month, American soldiers travelled to Armenia for a military exercise, infuriating the Kremlin.
Then there is Iran. Yerevan and Tehran have built an alliance and Iranian forces have been manoeuvring around its borders with Azerbaijan.