For nearly a hundred days now, the world has watched as the red lines ebb back and forth on the map of Ukraine. At first, a wave of hundreds of tanks, armoured vehicles and troop transports threatened to cut off Kyiv, before suddenly receding back to the border, leaving only shattered wreckage and broken bodies in its wake.

Now, it seems that Russian forces are changing their strategy. Unable to maintain the massive front they opened up across three sides of the country, with supply lines fraying and logistical disasters undermining the campaign, Vladimir Putin’s top brass is concentrating its efforts in the Donbas. More than half of Ukraine’s easternmost region had been held since 2014 by Moscow’s separatist proxies and, in the lead up to the war, the Kremlin formally recognised the claims of the two self-declared republics in Donetsk and Luhansk to the remainder.

Moscow now seems intent on pushing Kyiv’s troops out of the area, launching a savage assault on Severodonetsk, home – until recently – to more than 100,000 people. According to the local governor, Serhiy Hayday, the bombardment has been so heavy that it has been impossible even to count the dead. “The smell of corpses is constant, because they do not take away the bodies,” he said. As dust and shrapnel flies through its streets, Russian troops have moved in to claim what is left.

At the same time, Russia has succeeded in establishing and holding a land bridge along the coast down to Crimea despite fierce resistance, making it easier to move troops and equipment throughout the south. Mariupol, the port city defended for weeks by the garrison in the tunnels under the Azovstal steelworks, was captured earlier this month, ending the final major pocket of resistance in the area.

While its fall, and the surrender of hundreds, or even thousands of its defenders, was hailed by Russian propaganda as a major victory, few in Moscow seem prepared to publicly ask why it took so long to take a city just 30 miles from its own border. Instead, the Kremlin seems set to take out its frustration on its prisoners, with talk of setting up a war crimes tribunal continuing, despite having reportedly agreed to exchange them as part of a surrender agreement.

The second, more targeted, phase of the war has clearly begun. Having frustrated Putin’s ambitions and inflicted tens of thousands of losses on his armed forces, whether Ukraine can continue to hold the line remains to be seen. “It did look as if the conflict was turning in Russia’s favour in the past week,” says Dr Natasha Kuhrt, a lecturer in War Studies at King’s College London. “However, when you look more closely, they are concentrating incredibly hard on a much smaller area.” The question, it seems, is whether that is sustainable, and she warns that Moscow is already running low on supplies of tanks and other equipment, reinforcing with older gear.

Colonel Philip Ingram MBE, a former British military intelligence officer, agrees that the overall picture hasn’t improved for Russia. “They have simply limited their ambitions to taking the Donbas region, and this has the advantage of giving them shorter lines of logistic communications,” he says.

“Ukraine trades space for time – time to move counterattack forces into place and time to train on and integrate new weapon systems. This takes weeks and months, not days,” Ingram adds. “In the meantime, small Russian successes will continue in some places – they have a single focus and a unified command, which they never had before – but they are losing a lot of capability as the Ukrainian defenders are holding up well.”

The appointment of a single commander to oversee the struggling “special operation” was widely interpreted as a sign of Putin’s discontent with his top officers. General Aleksandr Dvornikov took the reins in April, according to US and European intelligence agencies, and has seemingly been tasked with doing whatever it takes to turn around the ailing offensive. A veteran of the Syrian war, he seems intent on using the same playbook that allowed Russia’s ally, Bashar al-Assad, to seize control of the bombed out shells of rebel-held cities, no matter the cost to civilians.

The shift in priorities is a major moment in this war, which began with Putin announcing a plan to “demilitarise and de-Nazify” Ukraine. Clearly expecting the former Soviet Republic to crumble as soon as the tanks started rolling, his ambitions to oust the government of Volodymyr Zelenskiy and destroy its armed forces have failed. While initially the vast Russian bureaucracy struggled to adjust to this reality – and it was unclear if even the President himself understood the dire situation on the ground – it is clear that the objectives have shifted to asserting control over the Donbas.

But even if they were successful in capturing all of the territory claimed as part of the unrecognised Donetsk and Lugansk People’s Republics, could Putin pass this off as a victory? “Absolutely yes,” says Dina Fainberg, an expert on Russian and Soviet propaganda at City University London. “That’s because of the control he has over mass media, but also because of how murkily defined the declared goals of the war are.”

According to Ingram, however, that outcome is not yet a done deal. “The West needs to speed up delivery of long-range artillery, air and aviation assets alongside more tanks and infantry fighting vehicles to ensure the Ukrainians have the ability to carry out decisive counter attacks in the near future,” he urges.

For the time being, though, US President Joe Biden has said his country will not hand over long-range rockets that could be used to strike targets on Russian soil, fearing an escalating standoff with Moscow. Likewise, Germany has come under fire after reports revealed almost none of the hardware it had pledged to donate has yet been delivered to Kyiv, despite repeated assurances it is not putting its economic interests before its obligations to its European allies.

Meanwhile, across Ukraine, the country’s defenders are digging in and bracing themselves for what may become a very long and very bloody few weeks.