General Dvornikov, 60, holds the second-highest rank in the Russian army. He was named a hero of the Russian Federation for his command of Russian forces in the brutal war in Syria, where Mr. Putin deployed Russian warplanes and missiles to help Syria’s president, Bashar al-Assad, in a multi-sided conflict among the government, armed rebels, jihadists and others. In September 2016, the general was appointed commander of Russia’s Southern Military District, with responsibility for the restive North Caucasus.
Russia had been running its military campaign against Ukraine out of Moscow, with no central war commander on the ground to coordinate air, ground and sea units. That approach helped to explain why the invasion struggled against an unexpectedly stiff Ukrainian resistance, and was plagued by poor logistics and flagging morale, American officials said.
The disorganized assault also contributed to the deaths of at least seven Russian generals, as high-ranking officers were pushed to the front lines to untangle tactical problems that Western militaries would have left to more junior officers or senior enlisted personnel.
Eric Schmitt reported from Washington, Jane Arraf from Lviv, Ukraine, and Michael Levenson from New York. Reporting was contributed by Andrew Higgins in Kosice, Slovakia, Thomas Gibbons-Neff and Natalia Yermak from Dnipro, Ukraine, Cora Engelbrecht from Krakow, Victoria Kim from Seoul, Julian E. Barnes from Washington, and Steven Erlanger and Matina Stevis-Gridneff from Brussels.