The rebels took control of about one-third of the Donetsk and Lugansk regions which make up Donbas at the start of a war that had left 14,000 dead on both sides by the time Russia invaded Ukraine on February 24.

Moscow recognised the so-called People's Republics of Donetsk and Lugansk as independent states three days before the invasion.

A month later, after failing to break through Ukraine's defences in the north, Russia revised its goals, saying its aim is the "liberation" of the entire Donbas, which stretches south to the besieged city of Mariupol on the Sea of Azov.

Before 2014, the Donbas had a population of about 6.6 million but many residents have since fled, either to other parts of Ukraine or to Russia.

Coal mines and steelworks

The Donbas encompasses an area about twice the size of Belgium on the border with Russia, which for centuries was controlled by members of the Ukrainian Cossack warrior caste and ethnic Tatars from the Crimea peninsula.

The economy of the Donbas took off after the discovery of coal in the 19th century.

During the Soviet era, Donbas miner Alexey Stakhanov became a poster boy for communism and a global symbol of productivity by using new tools to significantly boost mining output.

Strong Russian influence

After World War II numerous Russian workers were sent to work in the Donbas, creating strong cultural and economic links with Russia that endure to this day.

President Vladimir Putin claims that they and their Russian-speaking descendants in Donetsk and Lugansk need to be protected from Ukrainian forces, whom he accuses of "genocide".

Before the start of the rebellion in the Donbas, the city of Donetsk (formerly known as Stalino) was Ukraine's main steel-producing centre.

Since 2014, the city of Kramatorsk, where a missile strike on a railway station left at least 57 people dead on April 8, has become the de facto capital of the Ukrainian-controlled part of the Donbas.

Eight years of war

The war between Ukraine and the separatists in Donetsk and Lugansk erupted after the 2014 ouster of pro-Russian president Viktor Yanukovych in a popular uprising in Kyiv and Moscow's subsequent annexation of Ukraine's Crimea peninsula.

The rebels proclaimed two independent republics after holding referendums that were not recognised by the international community.

Kyiv and the West say Russia instigated the war in eastern Ukraine, pouring arms and troops across the border to bolster the rebels.

Attempts by Germany and France to mediate a lasting resolution of the conflict failed, with Kyiv and the separatists each accusing each other of violating a 2015 peace accord signed in the Belarus capital Minsk.