BAKHMUT, Ukraine — Months after dire warnings from Washington that Ukraine would not be able to hold Bakhmut against an onslaught of Russian mercenaries, Ukrainian forces still cling to the city’s western edge in what has stretched into the longest and most deadly fight of the war.

U.S. assessments were bleak as early as January, according to previously unreported classified U.S. intelligence documents leaked allegedly by Jack Teixeira, a member of the Massachusetts Air National Guard, and obtained by The Washington Post. Washington warned of the potential encirclement of Ukraine’s forces in Bakhmut and suggested Kyiv should cut its losses and let the city go.

An assessment marked “top secret” cautioned that “steady” Russian advances since November “had jeopardized Ukraine’s ability to hold the city,” and Ukrainian forces would probably be “at risk of encirclement, unless they withdraw within the next month.”

Those warnings have largely gone unheeded. Kyiv has framed holding Bakhmut as an imperative far greater than the city’s strategic military value, arguing it is needed to maintain national morale and deny Russia boasting rights over any territorial gain. Ukraine has said prolonging the fight in Bakhmut has sapped Russia’s strength by killing many soldiers, especially from the Wagner mercenary group.

The Ukrainian commander overseeing the fight for Bakhmut, Col. Pavlo Palisa, said he was never formally briefed on this U.S. intelligence or the recommendations on how to leverage the fight in Bakhmut for additional advantage.

“I’m not such a big fish,” he said, speaking from a basement command center.

Another document in the trove, a cache of sensitive materials leaked online through the messaging platform Discord, detailed ways Ukraine could use advanced munitions, information campaigns and counter-drone technology to “impose future costs” on Russian forces.

Palisa credited his ability to hold parts of the city for months longer than predicted to a combination of classic urban warfare and advanced drone reconnaissance, including layers of signal jamming.

After Russian forces breached Bakhmut’s perimeter, Palisa said he pulled his forces back into residential blocks, using rooftops as high ground and converting homes into antitank positions. Deeper inside the city, both sides began to rely heavily on reconnaissance drones for targeting and jammers to confuse the opponent’s navigation systems.

“Our enemy is using jamming really successfully,” he said, referring to measures that block access to GPS signals. “If we don’t have eyes in the air we can’t engage the enemy by artillery fire. Why it’s important is because we don’t have many artillery rounds. So our artillery fire must be precise.”

Palisa said Ukraine has also learned from Russian tactics, most recently employing equipment that masks a drone’s “home point” or coordinates that would reveal the location of the unit operating the device. “If they find our drones, it will give them information that the home point of the drone is somewhere in Australia,” he said.

When Palisa arrived at his post in mid-January, the assessments he heard from the officers around him echoed Washington’s pessimism. “Those guys said ‘I don’t know, maybe two or three weeks.’ But months later and we’re still here, trying to do our best to hold the city,” Palisa said, expressing confidence in the mission.

The leaked document also suggested worsening Russian morale and encouraging desertions with a “physiological operation campaign” highlighting the “expendability” of Moscow’s troops. Another bullet point encouraged Ukraine to target massed Russian forces with “dual purpose improved conventional munitions” — a combination of artillery and surface-to-air missiles — to counter assault waves.

When the defense of the city seemed untenable at critical moments, Ukraine repeatedly deployed elite units to protect supply roads and steady the situation.

While that strategy has succeeded, allowing Ukraine to maintain a hold on the city’s western edge, the front line has become increasingly unstable in recent days, according to commanders.

Inside the city, the basement of an apartment block serves as a small command center. Maps on the walls show the main front line along train tacks less than a mile to the west, as well as Russian advances from the north and south toward Ukrainian supply lines. The main road used to ferry munitions in and the wounded out is now within a few hundred meters of Russian positions.

“There is this fluid motion going on,” said a Ukrainian first lieutenant who asked to be identified by his call sign, Tatarin, in keeping with military protocol. Russian attacks along the front allow their forces to advance a few hundred meters before being pushed back hours later. “It’s hard to distinguish exactly where the front line is because it moves like Jell-O,” he said.

“The situation on the road is constantly moving,” Tatarin said, describing how positions shift throughout the day along Ukraine’s main supply road in and out of Bakhmut. “In the morning we can control it, and then we can lose it and take it back. But most of the time Ukrainian forces still control the road.”

Bakhmut is the main target of Russian operations in eastern Ukraine. Moscow has said capturing the town will lay the groundwork for taking control of Ukraine’s entire Donetsk region, of which Russian forces currently occupy slightly more than half.

In a statement Thursday, the Russian Defense Ministry said its forces led by airborne units “foiled the enemy’s attempts to counterattack” and to deploy reinforcements to Bakhmut’s north and south.

Outside Bakhmut, Ukrainian soldier Yan Melnikav commanded a battalion that has been defending Bakhmut’s edge since November, falling back to the northwest of the city as Russian troops advanced. He said Ukraine was able to extend the fight because its commanders on the ground were allowed to operate with greater autonomy than the Russians. When listening to intercepted communications, he said he often heard Russian commanders request permission from higher-ups to make small operational adjustments, which slowed their movements.

“We can cooperate directly with different units and when we are in a bad situation we can call on different units to help us out,” he said.

Once inside Bakhmut, the fight almost immediately slowed to a block-by-block slog. At times, the two sides would battle for weeks over control of a handful of residential blocks, Melnikav said.

“If you look at it in a strategic way, Ukrainian forces are holding a lot of enemy troops inside the city; it prevents them from going to different parts of the front line,” Tatarin said. “That’s why we’re holding on to the city, to eliminate as many enemy forces as possible.”

But the fight for Bakhmut has taken a significant toll.

Street-to-street fighting has become so intense over the past month that many Ukrainian units need to be rotated out of the city after just two weeks, according to the first lieutenant.

At the mortar unit on Bakhmut’s edge, soldiers under Melnikav’s command said the large number of munitions expended in the fight has forced shells to be rationed to six rounds a day, and resupply has become increasingly unreliable.

Palisa said ammunition shortages have repeatedly forced his troops inside Bakhmut to withdraw from their positions. “We don’t have enough rounds to engage them,” he said, “and I recognize we are paying with the lives of our soldiers.”

“I can give an assessment of the success of the mission only after everything is finished,” he said, dodging a question about whether the fight has been worth the lives lost and materiel spent. “Every soldier understands that when we are holding the city, when we are inside Bakhmut, we are giving time to our newly created units to train and prepare for future actions,” he said.

Russia has claimed that it was on the verge of capturing Bakhmut, which Russians call by its Soviet-Russian name, Artyomovsk, since September. But its gains have come in tiny increments at the expense of thousands of lives.

Ukraine’s determination to hold Bakhmut has also come at a high cost; the city is largely in ruins. Houses and apartment blocks have been shredded by the heavy use of artillery and streets, parks and gardens are littered with shrapnel. “I would like to see the city without all the destruction,” Palisa said. “But if it helps to save other Ukrainian cities, we need to do what we have to do.”

previous coverage

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• Multination training exercise at Fort Hood builds trust among allies, McConville says
• Ukraine planned attacks on Russian forces in Syria, leaked document shows
• ‘We can do both’: Indo-Pacific commanders rebuke Republicans who say Ukraine aid harms readiness for Chinese threat