Ukrainian soldiers train in the Kharkiv region of Ukraine, Oct. 17, 2026. Ukrainian brigades involved in Operation Vivaldi, which thwarted Russian efforts earlier this year to encircle the last cities of Donetsk Province, have begun to reveal details of how they managed to turn a losing defensive fight into a successful offensive. (Mauricio Lima/The New York Times) By CARLOTTA GALL and KAMILA HRABCHUK A steady hum of activity filled the underground bunker in eastern Ukraine. Soldiers called…
