KYIV, Ukraine — Ukrainian troops have broken through Russian positions outside the embattled eastern city of Bakhmut and forced Russian units back from a key position near a canal, military commanders on both sides said, in the first gains since March for Kyiv’s forces in the brutal fight for the city.
The advance was not large — roughly three square miles, southwest of the city, in an area of fields, ravines and thickets of trees — but it was acknowledged on Tuesday by Yevgeny V. Prigozhin, the head of the Wagner militia whose forces have been at the forefront of Russia’s fight for Bakhmut, and it was described on Wednesday by multiple Ukrainian military officials. Russia’s Defense Ministry did not comment on the reports.
Ukraine’s forces had not won any ground in the fight for Bakhmut since pushing Russian forces off a key access road two months ago, and it is far from clear that they can hold the terrain they captured this week or that it was a turning point.
But the 11-month battle for Bakhmut has taken on a symbolic significance that goes far beyond the city’s immediate strategic value and has come at devastating human cost for both sides. Both countries have invested resources and sacrificed soldiers in a high-stakes effort to wear each other down, with Russian forces slowly gaining control of most of the city and its surroundings.
The recent fighting there came amid an uptick in Ukrainian strikes behind Russian lines and reports of increased attacks in Russian regions bordering Ukraine, in advance of a major counteroffensive that Kyiv has said will begin soon. Ukrainian military officers said the advance near Bakhmut was an opportunistic strike as Russian Army troops were moving into position, one of several indications that it was not part of the broader push to retake Russian-occupied territory.
Gen. Oleksandr Syrsky, the commander of Ukraine’s ground forces, said in a statement that the Bakhmut attack was part of a “defensive operation” aimed at stalling the Russian assault on the city.
Ukrainian commanders from three units involved in the fighting gave details of the operation in interviews — the 3rd Separate Assault Brigade, a special forces unit; the Adam Tactical Group; and the Ukrainian Volunteer Army, which includes civilian volunteers.
Andriy Biletsky, who has overarching command of the Ukrainian 3rd Separate Assault Brigade, among other units, said in a video statement released early Wednesday that his troops had seized Russian positions and inflicted heavy losses on Russian troops. Two Russian companies, units typically with about 100 soldiers each, and a reconnaissance team had been “completely destroyed” in the fighting, said Mr. Biletsky, a former far-right politician and co-founder of the Azov Brigade.
Mr. Prigozhin, known for his outspoken and often-self-serving criticism of Russia’s military, said in a video on Tuesday that the Russian flank had been broken.
“Today they are tearing the flanks in the Artemovsk direction,” he said, using the Russian name for Bakhmut. He said that his forces would continue fighting in Bakhmut for now, though he threatened recently to pull Wagner mercenaries out of Bakhmut if they didn’t get more support from the Russian Army.
“We’ll keep pushing for a few more days,” he said. “Let’s fight.”
Mr. Prigozhin predicted, as others have, that the major Ukrainian counteroffensive would come in the Zaporizhzhia region, about 100 miles to the southwest of Bakhmut. The Ukrainian military has been regrouping in preparation for its assault, training troops to use newly delivered Western weapons and forming new units.
The Biden administration on Tuesday announced $1.2 billion in new military aid to Ukraine, including artillery ammunition and air-defense missiles, bringing the U.S. total since Russia invaded last year to about $37 billion.
The United States took a different kind of action on Wednesday, when the Justice Department said it had transferred millions of dollars seized from a Russian oligarch, Konstantin Malofeyev, for use in rebuilding Ukraine. It was the first action of its kind under a law enacted last year. Mr. Malofeyev is a prominent supporter of the war, and his assets were taken for violating economic sanctions.
Increasingly isolated from the West, Russia has tried to strengthen international ties where it can, including with the nation of Georgia, a former Soviet republic in the Caucasus that fought a brief war with Russia in 2008. On Wednesday, President Vladimir V. Putin ordered the restoration of direct flights from Russia to Georgia starting on Monday, and he abolished visa requirements for Georgian nationals to visit Russia, the latest sign of continued rapprochement.
But the Russian war effort continues to be plagued by internal dissension between Mr. Prigozhin and the regular military. In recent days, he has recorded graphic and expletive-laden videos accusing Russia’s senior generals of denying his forces necessary supplies, such as ammunition. On Tuesday, he appeared to take his attacks even further, publishing a video that some observers interpreted as a direct criticism of Mr. Putin.
Ukrainian weapons “kill our soldiers, while a happy grandpa thinks that everything is going well for him,” Mr. Prigozhin said in the video. Mr. Putin’s opponents commonly refer to him as “grandfather.”
On Wednesday, Mr. Prigozhin said that “grandpa” referred to a senior Russian military official whom he did not name. Mr. Prigozhin, a tycoon who earned his fortune in part through Kremlin catering contracts, has avoided direct criticism of Mr. Putin.
Mr. Prigozhin accused units of the 72nd Brigade of the Russian Army of abandoning their positions near Bakhmut. “Everyone fled and exposed a front almost two kilometers wide and 500 meters deep,” he said.
He added that his forces had to move in to prevent a further Ukrainian advance. “It’s good we managed to block it somehow,” he said.
A video filmed by a drone and sent to The New York Times by a commander of the Adam Tactical Group appeared to show Russian soldiers running in disarray, apparently after an artillery strike on their position in a tree line. Amid mud, shell craters and smashed trees, it showed soldiers fleeing from a burning bunker, one with his uniform on fire.
Another video, filmed from a soldier’s body camera and released by the 3rd Assault Brigade, which said it came from the scene of the fighting, showed a unit walking through a shallow ravine, stepping past dead Russian soldiers.
Neither video could be independently verified.
Col. Yevhen Mezhevikin, the commander of the Adam Tactical Group, said in a recent interview that the role of the forces fighting in Bakhmut was to prevent Russian advances while new brigades were being trained and assembled to carry out the expected counteroffensive. They also said that they sensed that the Russian Army was demoralized and thinly stretched in places along the front line, making it vulnerable.
A midlevel commander in the 3rd Assault Brigade who asked to be identified by his nickname, Zayan, in keeping with Ukrainian military rules, said of what might come next in the fight for Bakhmut: “Anything is possible.”
Carlotta Gall reported from Kyiv, Ukraine, Anatoly Kurmanaev from Berlin and Traci Carl from New York. Maria Varenikova contributed reporting from Kyiv, Ivan Nechepurenko from Tblisi, Georgia, and Charlie Savage from Washington.
