The Ukrainian Army is advancing in attacks near the eastern city of Bakhmut, Ukrainian commanders said on Friday, in fighting that has shifted the front line only slightly but is exposing fissures, confusion and alarm among Russia’s forces in the war. Russia’s pro-war bloggers were quick to claim that Ukraine’s long-anticipated counteroffensive had begun, but Ukrainian officials downplayed the advances and described them in more local terms. Ukrainian soldiers broke through Russian lines south of Bakhmut on Wednesday, they said, and then exploited that breach, assaulting Russian forces near the city and threatening Russian flanks to the north and south....