Ukraine's eastern front lines shifting ahead of major offensive

SLOVYANSK, Ukraine -- The front lines in eastern Ukraine are shifting in significant ways, with Russia and Ukraine carrying out offensive operations in and around Bakhmut.

Russian forces inside the city have made further advances and claim to have full control of every district.

Ukraine claims its forces are still fighting in a small area in the western fringe of the city.

Meanwhile, the situation outside Bakhmut is dynamic, with Ukrainian forces reporting a counteroffensive to the north and south of the city.

ABC News was allowed inside a military command center this weekend at an undisclosed location in eastern Ukraine.

Our team watched multiple screens showing live drone feeds down onto the battlefield in eastern Ukraine as a Ukrainian counteroffensive played out in real time near Bakhmut.

Ukrainian soldiers could be seen clearing Russian positions. Dead Russian soldiers were also visible on one of several live video feeds, which are monitored by Ukrainian soldiers.

That operation, which took place on Saturday morning, was one of a series of assaults by Ukrainian forces near Bakhmut in recent days.

Crucially, Ukraine claims it has taken control of higher ground near the city, which could give an important advantage for further attacks.

A Ukrainian commander whose battalion spearheaded an operation south of Bakhmut last week promised there would be more offensive action soon in the area.

The officer, who goes by his callsign "Rolo," commands as many as 700 men in the 1st Assault Battalion of Ukraine's 3rd Assault Brigade, which has been operating in and around Bakhmut for several months.

He told ABC News his men stormed Russian positions early in the morning last Wednesday, claiming that, by Thursday, his men had taken half a square mile of land and killed around 50 Russian soldiers. ABC News cannot verify his claims.

"We outplayed them," he said in an interview in a basement in eastern Ukraine.

The commander would not comment on whether the Ukrainian operation near Bakhmut was the precursor to a more significant counteroffensive by Ukrainian forces.

"Small steps lead to big results," he said with a smile.

"If you ask me, should we expect more? Yes, we should. If you ask me where, that's confidential. But you shall see it," the commander said, adding that new Western weaponry was filtering through to the battlefield.

"We have the initiate now. We dictate the rules," he boasted. "Now the enemy has to adjust to what we're doing and act according to our actions."

ABC News was also shown two US-supplied M113 armored personnel carriers which were badly damaged. According to Ukraine's 1st Assault Brigade they were used in the operation on Wednesday and Thursday to the south of Bakhmut.

Back at the military command center hidden in a nondescript building in Ukraine's eastern Donbas, the drone feed showed smoke rising over Bakhmut.

ABC News was unable to spot a building in the city on the live video feed which had not been badly damaged.

Most of the drones feeding the live front-line images back to the screens monitored by soldiers at the command center were commercial drones which can be purchased online, although many of the commercial drones are modified to carry and drop grenades.

The commander at the center, from Ukraine's Adam Tactical Group, Yevhen Mezhevikin, said Ukrainian forces "in every direction" along the front line were ready to go on a major counteroffensive "at any moment."

Speculating that the directions of a future Ukrainian counteroffensive had "already been chosen" by top Ukrainian generals, but were still being kept top secret, he said he was confident about Ukraine's chances.

He told ABC News that Ukrainian troops experienced successful counteroffensives earlier in the war, and argued that would give them an important edge.

"I'm sure we'll be able to break through enemy defenses on the front line and the enemy will have no success," he said in an interview.

Medics prepare ahead of expected counteroffensive

Doctors and medics at a military field hospital in Ukraine's eastern Donbas are also preparing for an inevitable spike in casualties when Ukraine launches a larger offensive.

"It is going to be difficult and we're going to have [an increase in] casualties," Dr Oleh Tokarchuk, the lead doctor at the military medical facility, near to the front lines, told ABC News.

"We're going to be losing our loved ones and friends but I believe we will be able to make it," he said.

Four wounded soldiers were brought back from front-line positions in military ambulances to receive treatment at the field hospital, in the roughly 90 minute period ABC News was there.

The soldiers were, according to medics, part of a tank crew which had been hit by Russian artillery.

One of the men had a serious shrapnel wound to his leg. Another, Vasily, who did not give his surname, had a minor injury to his arm.

"An artillery shell landed, some of us tried to take cover, some didn't," he said, looking visibly shaken but promising to return to the front lines once he has recovered.

Tokarchuk said the number of casualties arriving at his facility had significantly reduced since the early months of this year when Russia captured the town of Soledar, near to Bakhmut.

However, he said, his team were ready and prepared for that to change once a major Ukrainian counteroffensive gets underway.

"This is not rocket science," said Oleh Pankiv, a volunteer at the hospital who helps evacuate medical casualties away from the battle zone.

"When you have assault operations, you will always have many more injured people. But what can we do?" he asked.

"We need to stand our ground. We need to fight against the aggressor. And of course, we need to defend our country."

ABC News' Patrick Reevell contributed to this report.