ISW: Ukraine must not abandon its fortress belt in Donbass

From the Institute for the Study of War:

"Russian Offensive Campaign Assessment, August 8, 2025

Kremlin officials are reportedly demanding that Ukraine cede to Russia strategically vital unoccupied territory in Donetsk Oblast and freeze the frontline in other areas as part of a ceasefire agreement. Unnamed sources told Bloomberg on August 8 that Russian President Vladimir Putin demanded that Ukraine cede the entirety of Donetsk and Luhansk oblasts, along with Crimea, as part of ceasefire negotiations.[1] Bloomberg reported that this demand would require Ukraine to withdraw troops from Ukrainian-controlled territory in Luhansk and Donetsk oblasts that Russian forces have been trying and failing to capture since February 2022, after having failed to take it during Russia's initial invasion of Ukraine in 2014. Bloomberg reported that the terms stipulate that Russian forces would also halt offensives in Kherson and Zaporizhia oblasts while Ukraine and Russia negotiate a ceasefire and subsequent peace deal. Bloomberg reported that it is not clear whether Russia is willing to give up any land that it currently occupies...

The reported settlement notably does not include any mention of a Russian withdrawal from the occupied Zaporizhzhia Nuclear Power Plant (ZNPP) or from positions in Kharkiv, Sumy, Dnipropetrovsk, and Mykolaiv oblasts. Two European officials told the Wall Street Journal that US Special Envoy for the Middle East Steve Witkoff stated that the Russian proposal included two phases: the first in which Ukraine would withdraw from Donetsk Oblast and Russia and Ukraine would freeze the frontline, followed by a second phase in which Putin and US President Donald Trump would agree on a peace plan that they would later negotiate with Ukrainian President Volodymyr Zelensky...

Putin may be offering this proposal in an attempt to delay the sanctions that Trump threatened to impose by August 8 if Putin did not begin to negotiate with Ukraine to end the war.[5] Putin’s proposal demands the surrender of Ukrainian-held territory before a ceasefire, a sequence at odds with Trump's and Zelensky’s stipulation that a ceasefire must precede any peace negotiations.[6] US Secretary of State Marco Rubio stated on August 6 that a ceasefire is an important part of the negotiation process because it is difficult to negotiate a permanent peace deal while under fire — reiterating Trump's preferred timeline of establishing a ceasefire in Ukraine before starting formal peace negotiations to end the war.[7] The Wall Street Journal noted that European and Ukrainian officials worry that Putin is simply using the offer as a ploy to avoid new US sanctions while continuing the war.[8] Putin is likely deliberately offering a proposal designed to be unacceptable to Ukraine in order to delay sanctions as well as meaningful ceasefire negotiations and place the blame for the failure of negotiations on Ukraine.

The surrender of the rest of Donetsk Oblast as the prerequisite of a ceasefire with no commitment to a final peace settlement ending the war would position Russian forces extremely well to renew their attacks on much more favorable terms, having avoided a long and bloody struggle for the ground. Conceding such a demand would force Ukraine to abandon its "fortress belt," the main fortified defensive line in Donetsk Oblast since 2014 — with no guarantee that fighting will not resume. Ukraine's fortress belt has served as a major obstacle to the Kremlin's territorial ambitions in Ukraine over the last 11 years. The fortress belt is made up of four large cities and several towns and settlements that run north to south along the H-20 Kostyantynivka-Slovyansk highway, with a total pre-war population of over 380,537 people.[9] The line is 50 kilometers long (roughly 31 miles, about the distance between Washington, D.C. and Baltimore, Maryland). Slovyansk and Kramatorsk form the northern half of the fortress belt and serve as significant logistics hubs for Ukrainian forces defending in Donetsk Oblast. Kramatorsk currently serves as Donetsk Oblast's provisional administrative center (because Russian forces occupy the regional center of Donetsk City) and is a major industrial city.[10] Druzhkivka, Oleksiyevo-Druzhkivka, and Kostyantynivka serve as the southern half of the fortress belt. Ukrainian forces first began building up defensive positions in and around these cities after retaking them from pro-Russian proxy forces who attacked and seized Slovyansk, Kramatorsk, Druzhkivka, and Kostyantynivka in April 2014.[11] Ukrainian forces have maintained control of these cities since July 2014.[12] Ukraine has spent the last 11 years pouring time, money, and effort into reinforcing the fortress belt and establishing significant defense industrial and defensive infrastructure in and around these cities.

Russia's failure to seize Slovyansk in 2022 and ongoing struggles to envelop the fortress belt underscore the success of Ukraine's long-term efforts to reinforce the fortress belt cities... Putin's reported proposal reportedly demands that Ukraine concede this critical defensive position, which Russian forces currently have no means of rapidly enveloping or penetrating, apparently in exchange for nothing.

Ceding Ukrainian-held parts of Donetsk Oblast will place Russian forces on the borders of Donetsk Oblast, a position that is significantly less defensible than the current line... Russian positions along the Donetsk-Kharkiv and Donetsk-Dnipropetrovsk Oblast border areas would provide a more advantageous launching point for a future Russian offensive into nearby areas of Kharkiv or Dnipropetrovsk oblasts. ISW continues to assess that Russian forces will almost certainly violate any future ceasefire or peace agreement and renew military aggression against Ukraine in the future unless a peace agreement includes robust monitoring mechanisms and security guarantees for Ukraine.[23] Forcing Ukraine to concede the remainder of western Donetsk Oblast to Russia would bring Russian forces 82 kilometers further west in Ukraine...

Putin's reported proposal once again underscores that he maintains his uncompromising demands for Ukraine's capitulation and remains disinterested in good-faith negotiations. Putin stated on August 1 that the conditions laid out in his June 2024 speech “certainly” remain the same.[25] Putin demanded in June 2024 that any peace agreement must address the “root causes” of the war and provide for Ukraine's demilitarization, denazification, and alliance neutrality. Putin effectively demanded the removal of the current legitimate Ukrainian government and the establishment of a pro-Russian proxy government in Kyiv.[26] Putin has since consistently demanded that Ukraine concede all of Donbas and “Novorossiya,” referring to occupied and non-occupied parts of Donetsk, Luhansk, Kherson, and Zaporizhia oblasts as a prerequisite for any sort of negotiations with Ukraine.[27] Kremlin officials often invoke the term “Novorossiya” — an amorphous invented region in Ukraine — as an “integral” part of Russia in order to lay claims to territory beyond the four partially occupied oblasts and include all of southern and eastern Ukraine, including Dnipropetrovsk, Mykolaiv, and Odesa Oblasts.[28] Russian Foreign Minister Sergei Lavrov previously stated that there are “no secrets” about Russia’s demands and reiterated the importance of addressing the “root causes” of the war in a future peace agreement.[29] Putin stated on August 7, following his meeting with Witkoff, that, while not opposed to meeting with Zelensky, certain conditions must be “created” before Putin will meet with Zelensky, and that these conditions are still far away.[30] Putin’s efforts to posture himself as amenable to US peace proposals and meaningful negotiations while continuing to make the same demands and refusing to make any concessions are attempts to obfuscate the fact that Putin himself remains uninterested in ending his war on terms short of full victory. Putin and other Kremlin officials have also intentionally cultivated Russian society’s commitment to Putin’s stated war aims and have not set conditions to take any off-ramps to accept a peace settlement that falls short — in contradiction with Putin’s claims that he is interested in peace.[31]...

Key Takeaways:

• Kremlin officials are reportedly demanding that Ukraine cede to Russia strategically vital unoccupied territory in Donetsk Oblast and freeze the frontline in other areas as part of a ceasefire agreement.
• The surrender of the rest of Donetsk Oblast as the prerequisite of a ceasefire with no commitment to a final peace settlement ending the war would position Russian forces extremely well to renew their attacks on much more favorable terms, having avoided a long and bloody struggle for the ground. Conceding such a demand would force Ukraine to abandon its "fortress belt," the main fortified defensive line in Donetsk Oblast since 2014 — with no guarantee that fighting will not resume.
• Russia's failure to seize Slovyansk in 2022 and ongoing struggles to envelop the fortress belt underscore the success of Ukraine's long-term efforts to reinforce the fortress belt cities.
• Russian forces are currently still attempting to envelop the fortress belt from the southwest and are engaged in an effort to seize it that would likely take several years to complete.
• Ceding Ukrainian-held parts of Donetsk Oblast will place Russian forces on the borders of Donetsk Oblast, a position that is significantly less defensible than the current line.
• Russian positions along the Donetsk-Kharkiv and Donetsk-Dnipropetrovsk Oblast border areas would provide a more advantageous launching point for a future Russian offensive into nearby areas of Kharkiv or Dnipropetrovsk oblasts. ISW continues to assess that Russian forces will almost certainly violate any future ceasefire or peace agreement and renew military aggression against Ukraine in the future unless a peace agreement includes robust monitoring mechanisms and security guarantees for Ukraine.
• Putin's reported proposal once again underscores that he maintains his uncompromising demands for Ukraine's capitulation and remains disinterested in good-faith negotiations."