As Russia’s war in Ukraine enters a pivotal new phase, fighting is intensifying in the east of the country and officials have warned of a battle that “will remind you of the Second World War.”

Ukrainian Foreign Minister Dmytro Kuleba said Thursday that fighting in the Donbas region of eastern Ukraine was ramping up but that it “has not reached its maximum scale.”
“The battle for Donbas will remind you of the Second World War, with large operations, maneuvers, involvement of thousands of tanks, armored vehicles, planes, artillery. This will not be a local operation based on what we see in Russia’s preparations,” Kuleba said at a news conference in Brussels.
“Russia has its plan, we have ours, and the battlefield will decide the outcome,” he added.
Over the next few weeks, officials expect Russian forces to resupply and reposition with the aim of launching a brutal new offensive in Donbas, which encompasses the Luhansk and Donetsk regions, NATO Secretary-General Jens Stoltenberg said on Tuesday.
“We now see a significant movement of troops away from Kyiv to regroup, re-arm and re-supply, and a shift in focus to the east,” he told reporters in Brussels.”This is a crucial phase of the war.”
Already, much of the region has come under an unrelenting assault. Russian forces are trying to wipe the besieged southeastern city of Mariupol “off the face of the earth,” a Ukrainian military commander currently in Mariupol told CNN on Wednesday night.
Serhiy Volyna, Deputy Commander of the Marine Battalion in Mariupol, who has been fighting in the region since 2014, when Russia annexed Crimea, called the situation “critical.”
“It is a humanitarian catastrophe. The military that was involved in active hostilities here is completely surrounded. There are supply problems with water, food, medication, and general supply. It’s a very difficult situation.”
“We have been encircled in Mariupol for more than 40 days. The enemy outnumbers us and in terms of weaponry, their artillery, they have sea-based artillery, tanks, armored vehicles and of course mortars. It is difficult for us,” Volyna said.

Mariupol has come under sustained attack for weeks.

The Office of the United Nations High Commissioner for Human Rights (OHCHR) on Wednesday also listed the cities of Volnovakha, Izium, and Popasna as places where there have been “allegations of numerous civilian casualties.” Russian troops carried out 27 strikes on residential areas of the northeastern city of Kharkiv on Tuesday night, the head of the Kharkiv Regional Military Administration, Oleg Synegubov, said in a statement on Telegram.
Taking control of Mariupol would allow Russia to create a land corridor linking Crimea to Donbas, allowing troops to freely move from the southern peninsula to boost its units on the mainland.
But Russian troops have not yet been able to break through Ukrainian resistance across the east. They will likely attempt to encircle Ukrainian fighters in the east in the coming weeks, and whether or not they are able to do so could be crucial in determining the course of the war.

Russia reverts course

Since the war began, Russia has deployed a devastating array of aerial assaults across much of the country — using hugely destructive missile and artillery fire that extended well into the central and western parts of the country.
But a stuttering ground campaign and a series of military setbacks — particularly around the capital Kyiv and in the north — mean Moscow has made far less progress in capturing ground than most analysts expected.
Russian fighters moved out of the Kyiv region this week after Ukrainian troops regained control of the area containing the capital, while Russia has also failed to achieve complete air superiority in Ukraine and has suffered heavy losses of personnel since the start of the invasion.
Now, Russian President Vladimir Putin appears to be changing tack. Putin has revised his war strategy to focus on trying to take control of Donbas and other regions in eastern Ukraine with a target date of early May, according to several US officials familiar with the latest US intelligence assessments.
To achieve that goal, Stoltenberg said NATO is expecting Russia to conduct a “very concentrated” attack in the east aimed at capturing the entire Donbas region.
It’s too soon to say whether Putin has permanently abandoned his goal of taking Kyiv and overpowering resistance across Ukraine. But his shift in focus follows a series of losses elsewhere in the country that have stalled his invasion and stretched his forces.

Key new battlegrounds

Russian troops now are expected to try to cut off Ukrainian forces in the east and link up their troops across the region.
That means attention will likely soon turn to the city of Sloviansk, with an advance from Russian units from Izium to the north.
“Efforts by Russian forces advancing from Izyum to capture Slovyansk will likely prove to be the next pivotal battle of the war in Ukraine,” the Washington DC-based think tank Institute for the Study of War (ISW) said in its Monday update on the conflict in Ukraine. Its report uses alternative transliterations of Ukrainian place names.
A successful Russian assault on the city would give Moscow the option to link troops up with those fighting in Rubizhne, to the northeast of Sloviansk, or move them south, towards Horlivka and Donetsk, in an attempt to encircle Ukrainian fighters there, the group added.
But “if Russian forces are unable to take Slovyansk at all, Russian frontal assaults in Donbas are unlikely to independently break through Ukrainian defenses and Russia’s campaign to capture the entirety of Luhansk and Donetsk oblasts will likely fail,” the ISW said.
Vadym Denysenko, an adviser to the Interior Minister of Ukraine, agreed Thursday that the “the most difficult situation” Ukraine now faces is in the country’s east, where Ukrainian military officials say they have observed a buildup of Russian forces.
“Unfortunately, the Russians continue to do everything they did before in Kharkiv, Sumy, Chernihiv, and so on — to destroy civilian infrastructure,” he said. “The situation now is very difficult in the direction of Sloviansk and Kramatorsk,” Denysenko said.
“These are the key points at this stage of this war. I believe, in fact, the results of at least this stage of this war will largely depend on the fighting in the east.”

Families walk on a platform to board a train at Kramatorsk central station as they flee the eastern city on April 5.

What is the situation in the east now?

Cities across eastern Ukraine have suffered sustained and devastating Russian assaults for several weeks.
Mariupol, at the southern tip of the Donetsk oblast, has been particularly decimated and has come to serve as a symbol of the brutality of Russia’s war. In a roundtable on Wednesday, Mariupol Mayor Vadim Boychenko said more than 90% of the city’s infrastructure has been destroyed by Russia and that at least 40% of that is “no longer recoverable.”
5,000 people have died in the city in the first month of the invasion, including around 210 children, Boychenko said, citing preliminary estimates.
The humanitarian situation in Mariupol is meanwhile “growing worse and worse,” International Committee of the Red Cross (ICRC) spokesperson Lucile Marbeau told CNN on Wednesday. “Right now, there is nothing, no water, no electricity, barely any connection,” Marbeau said.

Around 90% of Mariupol's infastructure is believed to be destroyed, the city's mayor said.

But Mariupol is not alone; Ukrainian officials said Wednesday that major fighting was underway across Ukraine’s east, with the regional military governor of the eastern Luhansk region urging civilians to evacuate some towns.
Vadym Denysenko, an adviser to Ukraine’s Ministry of Interior, said: “If we talk about the key directions where combat will be ongoing — it’s the Sloviansk [Donetsk region] and Barvinkove [Kharkiv region] directions, in the Luhansk region it’s in the Popasna and Rubizhne areas and, of course, in Mariupol.”
Serhii Haidai, the military governor of the Luhansk region, issued a statement Wednesday calling for the evacuation of several towns in the region. “The Russians are destroying the railway connections of Donetsk region,” he said on Telegram.
“We will take everyone out if the Russians allow us to get to the gathering places,” he said. “As you can see, they do not always observe the ‘ceasefire regime.'”

What does Putin want in eastern Ukraine?

Pro-Russian separatists seized control of parts of the Donbas region in 2014, when Moscow reacted to protests that toppled a Kremlin-friendly Ukrainian president by fomenting a rebellion in eastern Ukraine. Fighting has endured there since.
When Putin began his invasion by sending troops into eastern Ukraine on February 22, he claimed that protecting the people of Donbas from “genocide” by the Ukrainian authorities was among the motivations — a false claim that was roundly dismissed by Ukraine and the international community.
That followed days of baseless claims about Ukraine’s sovereignty, and the decision by Russia to recognize two territories in Luhansk and Donetsk that were held by pro-Russian separatists. And since launching a full-scale war two days later, the supposed liberation of Donbas has played a central role in the rhetoric of the Kremlin.
The first weeks of the invasion saw bombardments of cities and towns well beyond that part of Ukraine; Russia invaded from the north, east, and south and focused much attention on Kyiv and other major cities, with strikes even reaching as far as Lviv in the far west of Ukraine.
But the revised strategy sees Putin return attention to the region that was at the heart of his attempts to justify the invasion. The Russian Defense Ministry’s daily summaries have sought to focus on successes in these regions and, over the past week, various Russian officials have described the Donbas region as the main goal of the operation, with other actions merely designed to pin down Ukrainian troops.
Drones, phones and satellite technology are exposing the truth about Russia's war in Ukraine in near real-time
“In the coming weeks we expect a further Russian push in the east and southern Ukraine, to try to take the entire Donbas and to create a land bridge to the occupied Crimea,” Stoltenberg said on Tuesday.
After six difficult weeks of war Putin is under pressure to demonstrate he can show a victory, and eastern Ukraine is the place where he is most likely to be able to quickly do that, several US officials familiar with the latest US intelligence assessments said. US intelligence intercepts suggest Putin is focused on May 9, Russia’s “Victory Day,” according to one of the officials.
But other officials note that even if there is a Russian celebration, an actual victory may be further off.
“Putin will have a victory parade on 9th May regardless of the status of the war or peace talks,” a European defense official said. “On the other hand: a victory parade with what troops and vehicles?”