BAKHMUT, JUNE 4Watching imagery from a drone camera overhead, Ukrainian battalion commander Oleg Shiryaev warned his men in nearby trenches that Russian forces were advancing across a field toward a patch of trees outside the city of Bakhmut.

The leader of the 228th Battalion of the 127th Kharkiv Territorial Defense Brigade then ordered a mortar team to get ready. A target was locked. A mortar tube popped out a loud orange blast, and an explosion cut a new crater in an already pockmarked hillside.

'We are moving forward,' Shiryaev said after at least one drone image showed a Russian fighter struck down. 'We fight for every tree, every trench, every dugout.'

Russian forces declared victory in the eastern city last month after the longest, deadliest battle since their full-scale invasion of Ukraine began 15 months ago. But Ukrainian defenders like Shiryaev aren't retreating. Instead, they are keeping up the pressure and continuing the fight from positions on the western fringes of Bakhmut.

The pushback gives commanders in Moscow another thing to think about ahead of a much-anticipated Ukrainian counteroffensive that appears to be taking shape.

Ukrainian Deputy Defense Minister Hanna Maliar said Russia sought to create the impression of calm around Bakhmut, but in fact, artillery shelling still goes on at levels similar to those at the height of the battle to take the city. The fight, she said, is evolving into a new phase.

'The battle for the Bakhmut area hasn't stopped; it is ongoing, just taking different forms,' said Maliar, dressed in her characteristic fatigues in an interview from a military media center in Kyiv. Russian forces are now trying - but failing - to oust Ukrainian fighters from the 'dominant heights' overlooking Bakhmut.

'We are holding them very firmly,' she said.

From the Kremlin's perspective, the area around Bakhmut is just part of the more than 1,000-kilometer (621-mile) front line that the Russian military must hold. That task could be made more difficult by the withdrawal of the mercenaries from private military contractor Wagner Group who helped take control of the city. They will be replaced with Russian soldiers.

For Ukrainian forces, recent work has been opportunistic - trying to wrest small gains from the enemy and taking strategic positions, notably from two flanks on the northwest and southwest, where the Ukrainian 3rd Separate Assault Brigade has been active, officials said.

Russia had envisioned the capture of Bakhmut as partial fulfillment of its ambition to seize control of the eastern Donbas region, Ukraine's industrial heartland. Now, its forces have been compelled to regroup, rotate fighters and rearm just to hold the city. Wagner's owner announced a pullout after acknowledging the loss of more than 20,000 of his men.

Maliar described the nine-month struggle against Wagner forces in nearly existential terms: 'If they had not been destroyed during the defense of Bakhmut, one can imagine that all these tens of thousands would have advanced deeper into Ukrainian territory.'

The fate of Bakhmut, which lays largely in ruins, has been overshadowed in recent days by near-nightly attacks on Kyiv, a series of unclaimed drone strikes near Moscow and the growing anticipation that Ukraine's government will try to regain ground.

But the battle for the city could still have a lingering impact. Moscow has made the most of its capture, epitomized by triumphalism in Russian media. Any slippage of Russia's grip would be a political embarrassment for President Vladimir Putin.

Michael Kofman of the Center for Naval Analyses, a U.S. research group, noted in a podcast this week that the victory brings new challenges in holding Bakhmut.

With Wagner fighters withdrawing, Russian forces are 'going to be increasingly fixed to Bakhmut ... and will find it difficult to defend,' Kofman told 'War on the Rocks' in an interview posted Tuesday.

'And so they may not hold on to Bakhmut, and the whole thing may have ended up being for nothing for them down the line,' he added.

A Western official who spoke on condition of anonymity said Russian airborne forces are heavily involved in replacing the departing Wagner troops - a step that is 'likely to antagonize' the airborne leadership, who see the duty as a further erosion of their 'previously elite status' in the military.

Ukrainian forces have clawed back slivers of territory on the flanks - a few hundred meters (yards) per day - to solidify defensive lines and seek opportunities to retake some urban parts of the city, said one Ukrainian analyst.

'The goal in Bakhmut is not Bakhmut itself, which has been turned into ruins,' military analyst Roman Svitan said by phone. The goal for the Ukrainians is to hold on to the western heights and maintain a defensive arc outside the city.

More broadly, Ukraine wants to weigh down Russian forces and capture the initiative ahead of the counteroffensive - part of what military analysts call 'shaping operations' to set the terms of the battle environment and put an enemy in a defensive, reactive posture.

Serhiy Cherevatyi, a spokesman for Ukrainian forces in the east, said the strategic goal in the Bakhmut area was 'to restrain the enemy and destroy as much personnel and equipment as possible' while preventing a Russian breakthrough or outflanking maneuver.

Analyst Mathieu Boulègue questioned whether Bakhmut would hold lessons or importance for the war ahead.

Military superiority matters, he said, but so does 'information superiority' - the ability 'to create subterfuge, to create obfuscation of your force, to be able to move in the shadows.'

Boulègue, a consulting fellow with the Russia and Eurasia program at the Chatham House think tank in London, said those tactics 'could determine which side gains an advantage that catches the other side by surprise, and turns the tide of the war.'