The two self-proclaimed rebel republics of Donetsk and Luhansk, whose independence Moscow recognized on Monday, are located in the rust belt of eastern Ukraine and escaped Kyiv s control in 2014.
More than 14,000 people have been killed in fighting between the Ukrainian army and the Moscow-backed separatists there.
Donetsk is surrounded by slagheaps, which is the main city in the Donbass mining basin.
It was once named Stalino and is a gritty industrial hub dominated by mining.
It is one of the main steel-producing centers in Ukraine.
Luhansk, the former Voroshilovgrad, is an industrial city of 1.5 million inhabitants.
They are grouped in the basin, on the border with Russia on the northern banks of the Black Sea, which is home to vast coal reserves.
There were about as many Russian workers sent to Russia after World War II during the Soviet era.
Since Russia annexed Crimea in 2014, the regions have been locked in armed conflict with Kyiv's army.
Their independence, proclaimed after referendums, is not recognized by the international community.
Kyiv and the West say Russia instigated the eastern uprising, pouring arms and troops across the border to bolster them.
On Monday, Russian President Vladimir Putin said he was recognizing their independence.
Donbass is at the heart of a cultural battle between Kyiv and Moscow, which states that the region, a large part of eastern Ukraine, is Russian speaking and needs to be protected from Ukrainian nationalism.
Efforts to resolve the conflict in eastern Ukraine, laid down in the 2015 Minsk agreements, are deadlocked. The separatists and Kyiv have accused each other of breaches.
A series of ceasefires have fallen through due to repeated violations by belligerents.
The political strand of the accords, which enables a large degree of autonomy for the rebel regions, as well as local elections under Ukrainian law, remains a dead letter, each side blaming the other for the failure.
Boris Johnson, British prime minister, denounced Russia's recognition of separatist republics as a flagrant violation of the sovereignty and integrity of the Ukraine. Each of the two republics have their own self-proclaimed presidents, and they are seeking full autonomy from the central government.
In 2018 at an election disputed by Kyiv, Denis Pushilin is the leader of the so-called Donetsk People's Republic, while Leonid Pasechnik is the leader of the separatist region of Luhansk.
Over the past few years, many warlords and separatists have been killed in attacks, victims of infighting or operations by the Ukrainian forces, according to reports that could not be verified.
Donetsk s rebel leader Alexander Zakharchenko, killed in a bombing at a Donetsk caf in August 2018, is the most prominent rebel victim in the conflict to date.