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STORY: Azerbaijan launched military action in the Nagorno-Karabakh region on Tuesday - a move that could foreshadow a new war.

It says it did so to drive out what it claims are Armenian troops.

Armenia and Azerbaijan were both members of the Soviet Union - and in the three decades since its collapse, they've already fought two wars.

Here’s a look at how we got here.

Nagorno-Karabakh is at the center of the conflict.

It's a mountainous region within Azerbaijan and is internationally recognized as part of it.

But it's known as Artsakh by Armenians - and its 120,000 inhabitants are predominantly ethnic Armenians.

They have their own government, which is close to Armenia, but not officially recognized by it or any other country.

Armenians, who are Christians, claim a presence in the area dating back several centuries before Christ.

Azerbaijan, whose inhabitants are mostly Turkic Muslims, also claim deep historical ties.

Bloody conflict between the two peoples goes back more than a century.

The region saw two wars after the Soviet Union crumbled - one that took place between 1988 and 1994 - and a second that lasted 44 days in 2020.

Over the course of the two wars, tens of thousands died.

In the first war, over a million people were displaced.

Most of those were Azeris, driven from their homes when Armenia ended up with control over Nagorno-Karabakh.

In the second - Azerbaijan managed to take back a third of Nagorno-Karabakh.

Russia brokered a ceasefire between the two - providing peacekeepers to guard the 'Lachin Corridor' - a crucial road that connects the territory to Armenia.

Analysts say successive rounds of talk have brought the two sides closer to a permanent peace treaty, but a final settlement remains elusive.

Tensions started ratcheting up again when a group of Azerbaijani civilians - identifying themselves as environmental activists - began blocking the 'Lachin Corridor.'

An Azerbaijan checkpoint was set up - blocking the flow of goods to Armenia.

It caused what the U.S. called a 'rapidly deteriorating humanitarian situation.'

The International Committee of the Red Cross (ICRC) was able to make aid deliveries this week.