Ukrainian government troops have made significant gains in recent days, pushing pro-Russian rebels out of a string of towns in the east. The rebels have retreated to Donetsk from Sloviansk, for weeks a powerful symbol of their resistance to Kiev.
So are Kiev's forces winning the conflict? Alexander Golts, a military expert and deputy editor of the Russian online newspaper Yezhednevny Zhurnal, examines the new stand-off.
Ukrainian politicians say a fundamental turning point has been reached in the conflict. But the experience of similar conflicts elsewhere - with a regular army confronting paramilitary units - provides no basis for such claims.
Nobody has succeeded in defeating paramilitaries who are embedded in a city, virtually turning its residents into a human shield - the Americans did not win such a conflict in Mogadishu, Somalia, nor did the Russians win in the Chechen capital Grozny.
In such a situation a regular army cannot use its superiority in heavy weapons over rebels - weapons such as armoured vehicles, aircraft and artillery.
The army may manage - after huge efforts - to capture one town, destroying it with heavy artillery, only to find that the rebels have simply moved to another town. That town in turn has to be taken by storm, and then the same thing happens in a third town.