Forcing Zelensky to hand Putin Ukraine’s ‘fortress belt’ in Donetsk will lose it the war

In the recent summit talks in Alaska designed to halt the Russia-Ukraine war, Vladimir Putin demanded that Kyiv cede control of the entirety of its Donetsk oblast (region) to Russia. But this would effectively be tantamount to an acceptance of overall defeat for Ukraine.

In giving up this region, Kyiv would also be giving up its principal defensive barrier against further Russian encroachment into the whole of Ukraine – that is, it will lose its “fortress belt”. This is the name given (by the Russians themselves) to a series of fortified Ukrainian-held cities, towns and settlements in the west of the Donetsk region. This belt roughly links the city of Slovyansk in the north to Kostyantynivka, some 50 km to the south.

The current situation on the battlefield needs to be viewed with a certain context in mind – that of geography. The state that we now call Russia (which has included Ukraine for much of its existence) has been subject to many invasions throughout its long history. Foreign invaders – whether coming from the east, south or west – were generally able to make rapid initial progress in their invasions, not least because Russia had few natural barriers that could act as defensive lines.

In particular, the open steppe lands, lacking hilly or mountainous terrain, have represented an open invitation to invaders. This issue still pertains. But today, ironically, these largely indefensible steppe lands are Ukrainian territory that is under threat from Russian forces.

In light of this, Kyiv cannot rely on terrain to form defensive lines. It has to rely on creating urban barriers. Towns and cities are notoriously difficult to capture or to fight through. Buildings, especially large ones, provide ideal cover and fire points for defenders. Getting into urban areas is difficult because of the channelling effect of the road systems. Obvious routes can be well defended with mines, obstacles and covering fire. Rubble also makes movement difficult. Urban scenarios very much favour the defender.

The normal tactic for an assaulting force would be to try and outflank and surround such urban areas and to then to essentially lay siege to them to prevent their resupply and thus force their surrender. This is what happened, but on a smaller scale, with the capture of Mariupol by Russian forces early in the war.

The other alternative has been to “squeeze out” Ukrainian forces from any town they are holding. In such scenarios, towns have been enveloped on three sides by Russian troops. This has then forced the under-pressure Ukrainians to withdraw though the only remaining egress routes. Russian forces then occupy the abandoned town.

This is what happened at towns that Ukrainian forces lost earlier in the Donbas region: Avdiivka, Bakhmut and Soledar.

But both of these forms of attack on urban areas are currently being denied to Russian forces. This is because of the complex series of Ukrainian defensive lines that have been established now between the series of towns and cities in the Donetsk fortress belt. These make use of minefields, anti-tank obstacles, enfilading fire (firing along the enemy line to inflict maximum casualties) provided by tube artillery and copious drone use.

Because the Russians have largely been unable to break through these lines they have been prevented from surrounding or enveloping any of the major urban areas within the fortress belt.

Last line of defence

It is strategically vital for the Ukrainians that this belt continues to hold back the Russians. It appears that one of the main aims of the 2025 summer offensive by Moscow (according to Russian officers captured by the Ukrainians) has been to break through this belt. It was said to represent the “poslednii ryvok” (the “final push”) that would settle the war’s outcome in Russia’s favour.

But this has not happened and looks unlikely to happen anytime soon. Indeed, as the Institute for the Study of War put it recently, Russian forces “are engaged in an effort … to seize [the ‘fortress belt’] that would likely take several years to complete”.

Hence, it becomes easier to understand why Putin needed to make the demand that he did at Anchorage. What cannot be achieved on the ground in terms of breaking through the fortress belt he is trying to achieve via a peace deal brokered with US assistance.

Gaining control of the west of the Donetsk region is the key to winning the war. Putin knows this. If Donetsk and its fortress belt are given up, then the open steppe land to the west would be exposed to Russian advances. Great swaths of Ukrainian territory would rapidly fall.

As one Russian source put it this week, the fortress belt “is the last serious line of defence for the Ukrainian Armed Forces. Beyond it, Kyiv has no other prepared lines of defence to Zaporizhzhia and the Dnipropetrovsk region … [and] … the Russian army can … advance to the Dnieper River”.

If Russian forces came to be camped on this part of the Dnieper, then it’s hard to imagine that Ukraine would not then have to accede to yet further, strategically damaging, territorial demands from Moscow. With such a scenario in mind, the future course of the whole war hinges on Ukraine not giving up its fortress belt in western Donetsk.

Perhaps an irony in Putin’s demand that the whole of the Donetsk region be handed over is that it could be seen as coming from a position of what appears to be weakness and not strength. He cannot wait the years it may take to seize the cities and towns that form the fortress belt. Russia cannot remain on a war footing for too much longer, according to reliable reports on the state of its economy.

But even so, Kyiv may have to accede to Putin’s demands because it will potentially come under pressure from the Trump administration, which itself does not want to wait years to see a resolution to this conflict. If Kyiv does accede, though, then this may amount to Ukraine accepting its overall defeat. It may, indeed, lose the war.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.