Russia is slowly closing in on Sloviansk and Kramatorsk, two heavily fortified cities in eastern Ukraine whose capture would bring Moscow closer to controlling the entire Donetsk region.
But these are not simply two more cities on the map.
Sloviansk and Kramatorsk occupy a special place in the history of this war. It was here, in April 2014, that the confrontation in Donbas transformed from political unrest into an armed insurgency and some of the first serious fighting between Ukrainian forces and Russian-backed fighters began.
Twelve years later, the war is returning to where it started.
Russian forces are now less than 15 kilometres from Sloviansk and Kramatorsk, according to military analysts, while both cities are coming under increasingly frequent drone, artillery and guided-bomb attacks.
Together with Druzhkivka and Kostiantynivka, they form what Ukrainian military planners call the Donetsk “fortress belt”: a chain of urban and industrial settlements that has become the backbone of Ukraine's remaining defences in the region.
Russia has spent years trying to reach it.
The geography explains why.
Sloviansk anchors the northern end of the defensive belt. Kramatorsk, immediately to its south, has served as the administrative centre of Ukrainian-controlled Donetsk since separatists seized the regional capital, Donetsk city, in 2014.
Further south lie Druzhkivka and Kostiantynivka, creating a roughly north-south urban corridor that Ukraine has spent years fortifying.
These are cities, factories, apartment blocks, railway lines, roads and industrial zones rather than open countryside. That gives defenders positions from which to fight and creates exactly the kind of dense terrain that can make an attacking army pay heavily for every kilometre.
Russia is therefore trying to weaken the belt before attempting to break through it.
Russian forces have been striking bridges around Kramatorsk and they are closer to Druzhkivka. Kostiantynivka has been captured by Russian forces.
Sloviansk carries an importance that goes beyond military geography.
On April 12, 2014, armed men led by Igor Girkin, also known as Strelkov, seized police and security-service buildings in Sloviansk.
Weapons were taken from police armouries, checkpoints appeared around the city and armed groups declared allegiance to the self-proclaimed Donetsk People's Republic.
Kramatorsk was targeted the same day.
Ukraine responded by launching what it called an “anti-terrorist operation.”
Sloviansk subsequently became one of the first major battlefields of the Donbas war.
For nearly three months, Ukrainian forces fought to retake the area. Artillery fire, checkpoints, kidnappings and street fighting transformed what had been an ordinary industrial city into an early symbol of the conflict.
Then, in July 2014, Girkin's forces withdrew.
Ukrainian troops retook Sloviansk, Kramatorsk, Druzhkivka and Kostiantynivka, raising the Ukrainian flag over the cities on July 5.
The separatist forces retreated towards Donetsk.
That withdrawal helped create the front line that would divide the region for the next eight years.
Now Russia is approaching those same cities again, this time with its regular army.
Their defence has become so important that Kyiv has placed some of its best-known commanders in charge of the region.
Andrii Biletskyi, commander of Ukraine's Third Army Corps, and Denys Prokopenko, commander of the First Corps Azov, have been given major roles defending Donetsk under Ukraine's new top commander, Mykhailo Drapatyi.
Russian forces now appear to have the battlefield momentum. Ukraine still benefits from prepared defensive positions and increasingly sophisticated drone warfare, but Russian troops are steadily closing in, applying pressure along multiple approaches and exploiting weaknesses in the fortress belt. Moscow's advance remains costly and uneven, yet the initiative is increasingly on Russia's side, and Ukrainian forces face the growing risk that the defensive line could be breached.
Analysts believe September and October could therefore produce some of the year's fiercest fighting, particularly if worsening weather reduces the effectiveness of drones and gives Russia opportunities to attempt larger mechanised assaults.
For Vladimir Putin, the objective is straightforward.
Russia controls most, but not all, of Donetsk. Ukraine continues to reject Moscow's demand that it surrender the remaining territory it holds there.
Taking Sloviansk and Kramatorsk would not automatically complete Russia's conquest of Donetsk, but breaking the fortress belt would remove the strongest remaining Ukrainian defensive system protecting the region.
For Ukraine, losing it would mean far more than losing another stretch of territory.
Sloviansk is where armed men seized government buildings in April 2014 and where Kyiv first fought to prevent the Donbas insurgency from spreading unchecked.
Ukraine retook the city once.
Twelve years later, Russia is coming back for it.
