U.S. expects fighting to intensify in Donbas region of Ukraine

U.S. officials expect the fighting to become more intense as Russia's main effort shifts to the Donbas region because more forces will be concentrated in a smaller geographic area.  

The officials consider Mariupol, in southeastern Ukraine, as the linchpin. If and when it falls, the Russians will be on the left flank of the Ukrainian armed forces who have been fighting in the Donbas. Control of Mariupol would give Russia access to a major port, and it would create a land bridge extending from the Donbas, in eastern Ukraine, to Crimea, in the south, allowing Russia to open up its resupply lines.

The Russian defense ministry earlier this week announced it would reprioritize eastern Ukraine over its efforts in the North, specifically against Chernihiv and Kyiv, the capital.