Donbas: Why Russia is trying to encircle Ukraine's east

Russia has pulled troops away from Kyiv and shifted most of the focus of its war to eastern Ukraine, after a series of defeats near the capital. This push into the area known as Donbas could mean a protracted conflict.

What would Vladimir Putin need before he could claim his goal of "liberating" Ukraine's old industrial heart and is that possible?

Russian forces have already triggered a humanitarian catastrophe in the east, reducing Mariupol to ruins, but they have failed to inflict defeat on Ukraine's military.

Preparing for a reinvigorated Russian onslaught on the east, President Volodymyr Zelensky vowed: "We will fight for every metre of our land."

Ukraine's best-trained forces were already posted in the east because of an eight-year war with Russian-backed separatists. They are thought to have suffered heavy losses, but are still a significant challenge to Russia's invading army.