Ukraine’s ‘Operation Vivaldi’ pushed Russian forces back around Lyman in the Donbas. Now both armies are massing troops for the next battles farther south.

Andriy Biletsky, commander of Ukraine’s 3rd Army Corps, said this week that his units are successfully carrying out Operation “Vivaldi.” The first of its four phases, he said, is nearing completion: Russian units near the town of Lyman, which had been trying to push through to the Siverskyi Donets R