A meandering river in eastern Ukraine is hindering both sides in the war

The war in Ukraine will soon be three months old. Russia's forces are still well short of the minimum objectives set out by President Vladimir Putin and in many areas the front lines are beginning to look static. But after weeks of intense bombardment, the Ukrainians' defensive lines in the east are also degraded.

Essentially, two battlegrounds are emerging. The Russians are adding combat power to their drive to take the Luhansk and Donetsk regions. The Ukrainians are trying both to hold them back and to cut them off. It's a three-dimensional chessboard of military calculation. And the natural boundaries shaped by one river in eastern Ukraine are already affecting the progress of each side.

Russian forces have taken territory -- but in modest amounts. Many of their gains, especially in the south, came in the early days of the invasion, and they have tried to consolidate those. At the epicenter of the conflict -- in the industrial belt of Luhansk region -- they have resorted to blanket bombardment.