The Russian army penetrates Kostiantynivka, a key stronghold of Ukrainian defense in Donbas

KramatorskIn recent months, Ukraine has deployed a successful campaign ofdeep attacks on Russian refineries and supply routes to Crimea with medium-range drones, which has generated optimism among European allies and Western analysts. But, despite these good results, the advance of Russian troops in Donbas – a region formed by the provinces of Donetsk and Luhansk, the latter now almost entirely occupied – seems inexorable and has accelerated with the battle of Kostiantynivka, an enclave south of the large Ukrainian defensive line in Donetsk, where Ukraine still holds a quarter of the territory.

Known as the fortress belt, this extensive fifty-kilometer military infrastructure is connected by a long road that for years has been the backbone of Ukrainian defense of the area, under the name of the Kramatorsk agglomeration. From Sloviansk in the north, passing through Kramatorsk, Druzhkivka, and finally Kostiantynivka, this perimeter remains the main barrier to Moscow's long-standing ambitions to conquer all of Donbas. Spokespersons for the Ukrainian brigades deployed in Kostiantynivka, the most active sector of the battlefield, on Tuesday rejected the version initially given by the chief of the general staff of the Russian army, Valery Gerasimov, according to which the Kremlin's forces had captured the city and achieved a significant strategic success.

"Kostiantynivka is one of the main enemy advance routes towards the Kramatorsk-Sloviansk axis. That is why the Russians spare no effort or resources. We inflict significant losses on them, but the replenishment of personnel is constant, which is why the situation remains very tense," stated Ukrainian commander Oleksandr Rashevsky in a comment published on his official Telegram channel. Ukrainian President Volodymyr Zelensky, mocking the scarce public appearances of his Russian counterpart and his reluctance to visit the front, said that if Russia had really captured Kostiantynivka, then "Putin would have no problem" going there to talk about peace. The content published from the front by the Ukrainian side and the comments of Russian military bloggers attest to the Ukrainian version of the situation in Kostiantynivka and cast doubt on the Kremlin's official version of the city's capture.

Drone saturation

The constant aerial surveillance by reconnaissance drones has led to large-scale offensives being replaced by infiltration warfare: a military tactic where small groups of Russian soldiers are gradually occupying positions in a destroyed, often confusing urban environment that blurs the front line. In this muddle, combatants may be dressed as civilians or wear uniforms of the opposing side. The sole objective is to hold the position in a basement or building ruins until support troops arrive, without using logistical or evacuation routes that could indicate to Ukrainian drones the refuges where they are hiding. Being wounded or not well-supplied can be a direct death sentence. Ukrainians also suffer this isolation: holding or reinforcing positions and evacuating the wounded has become increasingly difficult under the constant presence of drones. Success on the battlefield is measured in meters, not kilometers.

"The Russian army already controls one-third of Kostiantynivka with troops, but the entire city is infiltrated. It will fall within weeks," states Konrad Rochan, a Polish defense analyst from the Rochan Consulting group, a regular collaborator with international agencies and media. Based on open-source intelligence and the track record of Russian units, Rochan details that the strategy is to reach the flanks of Kostiantynivka to take advantage of the topography and occupy elevated terrain, from where they can deploy drones with greater visibility and advantage and attack the neighboring cities of Druzhkivka and Kramatorsk. In the north of the belt, however, Ukrainians are executing counterattacks in Lyman, where they have fortified themselves to protect the access route from Izium to Sloviansk, a fundamental logistical node for the Ukrainian army.

For Rochan, the Ukrainian campaign in Crimea that affects the supply lines of Russian troops, or the one that impacts with the arrival of drones in Moscow or Saint Petersburg, does not generate significant impact on the situation of the Donbas front beyond causing instability in the Russian economy and politics. The Kremlin's ideal timelines, which would mark a resounding success, would be to reach the gates of Kramatorsk and Sloviansk by the end of the year. What is happening in the south of the country is not decisive in Donetsk, but there is a perception of higher morale among the soldiers thanks to these successes, according to the fixer Gregory Shcherban, who usually deals with soldiers at the front.

Ukraine's response to the challenge of Kostiantynivka could be crucial in deciding whether this industrial city – with a population of seventy thousand inhabitants in peacetime – will be known as the last great fortress that Russia conquered, or as the beginning of the end for Donbas under Russian control. If it falls, Russian forces could push the Ukrainian army towards Ukraine's last remaining strongholds in the belt and move closer to conquering all of Donbas, one of the Kremlin's key objectives in this war.