Let’s take a closer look at another danger hidden behind Putin’s demand that Ukraine pull its forces out of the Donetsk region — a threat that most political and diplomatic experts tend to overlook, and that the military rarely speak about openly. It directly targets Ukraine’s strongest position in the east: the Sloviansk–Kramatorsk agglomeration. This is the “fortress belt” we have painstakingly built and held since 2014, a vital line that has consistently stopped Russian forces from pushing deeper toward central and western Ukraine.
Virtual tour along the H-20 highway: the eastern shield of Ukraine’s armed forces
For most Ukrainians, this defensive line is a story rarely told. So, let’s take a virtual tour. Picture yourself sliding into an imaginary car and heading south from Sloviansk — the northern “anchor” of the fortress belt along the H-20 highway. This road ties Sloviansk to Kramatorsk, Druzhkivka and Kostyantynivka, before stretching on toward the temporarily occupied Donetsk and Mariupol. Ukrainian military calls the H-20 the main spine holding these cities together. Running alongside it is another lifeline — the M-03 highway, linking the area to Kharkiv and Izium, and keeping reinforcements and ammunition flowing in from the north.
The Kazennyi Torets River, a tributary of the Siverskyi Donets, threads its way through Sloviansk, Kramatorsk and Druzhkivka, creating “watery” defensive lines and a series of natural barriers to vehicles. Rising above it all is Karachun — the commanding height south of Sloviansk, watching over the approaches and effectively “guarding” the northern gateway to the agglomeration.
The first stretch of the Sloviansk–Kramatorsk defence line runs with the Kazennyi Torets valley to the right and, straight ahead, a cluster of industrial buildings and embankments that have been methodically folded into the defensive network since 2014. At its core stands Kramatorsk — the city that anchors the entire line. Today, it serves as both the temporary administrative centre of Donetsk region and a vital logistics hub on the banks of the Kazennyi Torets. Cities like this work as “anchors,” allowing for repairs, medical evacuations, ammunition deliveries and troop rotations without having to push the rear positions too far west.
From Kramatorsk, the route leads to Druzhkivka and Oleksiievo-Druzhkivka — a tightly packed urban belt of industrial zones, quarries, slag heaps, high embankments and railway spurs, each lending itself naturally to strongpoints and firing positions. Here, the fortress belt fuses the terrain and the road network into a single, mutually reinforcing system that’s hard to skirt around and even harder to punch through without heavy losses.
The line’s final link is Kostyantynivka, where modern engineering defences are everywhere: tunnel-like passages shielded with anti-drone mesh along approach roads and streets, a stark sign of how urban warfare has adapted to the relentless FPV drone threat.
What we’re looking at here is a multi-layered fortification system built on three lines — military, engineering and administrative. Threaded through these are trenches, anti-tank ditches, “dragon’s teeth,” deep dugouts and bunkers. This is where our virtual tour has to end, because the exact positions remain classified.
One more feature of this agglomeration is just as critical — the heavy mining of the surrounding areas. I know a colonel who’s been laying these mines since 2014. When I asked him what chance the Russians had of getting through, his answer was blunt: none. The approaches to this area have been mined and re-mined, creating a barrier that forces the enemy to burn time and manpower on demining operations — all while under fire.
This chain of “anchor” cities along the H-20 axis — Sloviansk, Kramatorsk, Druzhkivka, Oleksiievo-Druzhkivka, Kostyantynivka — isn’t just a string of fortress towns. It’s a 50-kilometre urban-industrial ridge, with dense development set on commanding terrain: dominant heights like Karachun, river valleys, embankments, and sprawling industrial sites. The Russians have been trying — and failing — to encircle it since 2014.
Ukrainian forces and ISW analysts are blunt: giving up this strip wouldn’t just erase Donetsk’s strongest defensive line — it would set the stage for a far greater military disaster nationwide.
What if Ukraine surrenders the Donetsk region to Russia?
If Ukraine is forced to pull back beyond Donetsk’s administrative border, we’ll be staring down the barrel of a strategic disaster. Abandoning western Donetsk wouldn’t just erase our hard-won “belt of fortresses” and push the front line 82 kilometres to the west — it would hand Russia prime staging grounds for its next offensives. From there, the Kremlin’s forces would spill onto the open eastern Ukrainian plain, where the steppe runs unbroken to the borders of Dnipropetrovsk and Poltava. It would also reopen the threat of pressure on Izium and give Moscow fresh positions from which to menace Kharkiv.
We’d then be scrambling to throw up new fortifications from scratch along the borders of Kharkiv, Poltava and Dnipropetrovsk — assuming we have the time. Out in the open, with no natural cover, our troops would be easy prey for Russian glide bombs and missiles, cut down as if in a shooting gallery.
The harsh lesson of 1938
For those who dismiss this scenario as far-fetched and cling to the idea of peace at any price, remember the fate of Czechoslovakia.
In 1938, the world cheered the Munich Agreement. Chamberlain promised “peace for our time,” while Czechoslovakia was forced to cede the Sudetenland to Nazi Germany. This mountainous strip, bristling with thousands of concrete bunkers and artillery casemates — the so-called “Beneš Line” — was the shield guarding Prague and the core of Czech industry. Stretching more than 1,200 kilometres along the borders with Germany and Austria, it was anchored in high ground that offered a formidable natural defensive edge.
Military historians agree the line could have held out for weeks, even months, against a Wehrmacht assault, forcing the Germans into punishing mountain battles. At the time, the Czechoslovak army had 1.25 million troops mobilised, backed by modern artillery and home-built armoured vehicles.
German generals later admitted that breaking through those defences would have cost the Wehrmacht staggering casualties. General Keitel was blunt: “Had the Czechs fought, we would have suffered colossal losses.”
Less than six months after losing its main defensive line, Czechoslovakia was occupied. The Sudetenland — once meant to deter an aggressor — became a springboard for the German advance. Today, we are being pushed to make the same mistake.
The Sloviansk–Kramatorsk agglomeration is Ukraine’s “Sudetenland” — a chain of towns, industrial zones, river valleys and commanding heights, turned into a fortified strip that has held firm since 2014, blocking Russian pushes along a narrow front. Losing it would open the way for the enemy to spill onto the unbroken steppe, with direct routes to Kharkiv, Poltava and Dnipro.
We’ve already heard the talk: “peace in exchange for territory.” But history leaves little doubt — give up a fortress line, and you’re not buying peace. You’re throwing open the gates to the next occupation.
