Russian forces are steadily increasing pressure on Ukraine's remaining strongholds in the Donbas, with incremental battlefield gains raising the prospect that Moscow could soon bring its offensive to the doorstep of Sloviansk and Kramatorsk, the two largest Ukrainian-controlled cities in the region, reported pro-Ukrainian outlet AMK Mapping.

Although the front line has not collapsed and Ukraine continues to contest Russian advances, military analysts say the campaign has entered a critical phase as Moscow concentrates forces against what Ukrainian soldiers have long referred to as the Donbas "fortress belt" — a chain of heavily fortified industrial cities that has anchored Kyiv's eastern defences for years.

The immediate focus of Russian operations is Kostiantynivka, an important logistics hub linking Sloviansk, Kramatorsk and Druzhkivka. Russian forces have advanced on several axes around the city, attempting to envelop Ukrainian positions while gradually expanding their foothold on its outskirts.

Russian military officials have made claims suggesting they have captured Kostiantynivka, but those assertions have not been independently verified. Ukrainian officials continue to report heavy fighting inside and around the city, indicating that control remains contested.

Even without a rapid breakthrough, analysts say the broader operational picture is becoming increasingly favourable for Russian forces.

Recent advances have enabled Moscow's troops to establish control over substantial sections of elevated terrain stretching between the Bakhmut-Siversk line and the defensive belt centred on Sloviansk, Kramatorsk and Druzhkivka.

The tactical importance of these ridgelines extends beyond simple territorial gains.

Control of higher ground would allow Russian forces to move artillery, multiple-launch rocket systems and drone units closer to Ukrainian rear positions, expanding the area vulnerable to sustained bombardment while improving reconnaissance and strike capabilities.

AMK Mapping noted that once Russian artillery can effectively cover approaches to Sloviansk and Kramatorsk, Ukrainian logistics and troop movements could become considerably more difficult, even before full-scale urban battles begin.

Russian commanders also appear to be focusing on eliminating the remaining fortified Ukrainian positions between Siversk and Sloviansk, seeking to secure uninterrupted control of the elevated terrain before pressing further west.

Unlike earlier phases of the war, the offensive has relied less on large mechanised assaults and more on gradual attrition.

Russian assault groups have increasingly operated in small infantry formations, using dense summer vegetation to infiltrate Ukrainian positions, identify weak points and establish forward footholds before heavier weapons are brought forward.

The tactic has reduced the visibility of advances while limiting the exposure of armoured vehicles to Ukrainian drones and artillery.

Analysts say the approach has enabled Russia to make slow but consistent territorial gains.

Should Russian forces secure Kostiantynivka, pressure would likely increase on Druzhkivka, which is connected to Kramatorsk through a largely continuous urban area. Military observers say this built-up terrain could provide opportunities for further infiltration operations while complicating Ukraine's efforts to establish new defensive lines.

Reports from the battlefield indicate Russian forward assault groups have also moved closer to Kramatorsk from the southeast, although the precise distance to the city's outskirts cannot be independently verified.

For Ukraine, the defence of Sloviansk and Kramatorsk carries significance beyond their military value. Together, the cities represent the administrative and logistical centre of the remaining Ukrainian-held portion of the Donetsk region. Their loss would mark Russia's most significant territorial gain in eastern Ukraine since the capture of Bakhmut and Avdiivka and would substantially advance Moscow's long-stated objective of seizing the entire Donbas.

At the same time, analysts caution that urban warfare has repeatedly slowed Russian offensives throughout the conflict. Previous battles for cities including Bakhmut, Avdiivka and Chasiv Yar lasted many months and required enormous expenditures of manpower and equipment despite Russia's numerical advantages.

As a result, while Russian battlefield momentum has increased in recent weeks, the outcome of the campaign remains uncertain. Much will depend on Ukraine's ability to reinforce threatened sectors, conduct local counterattacks and disrupt Russian logistics before Moscow can fully exploit its recent tactical gains.