"I'm not sure either side has the chance for a big offensive," he said, a problem for Russia's generals as they promise fresh victories.
Vadym, an officer in the 63rd brigade fighting around Lyman, credited the fortress belt successes to military reforms in 2024 that improved coordination.
"Before, a single brigade would stand its ground and then be outflanked. Now you can feel the difference.
It is better," he said. "We started creating proper kill zones.
Over the last six months in our sector we haven't given the Russians a single metre."
None of which means Russian troops have not advanced in places.
In Kostyantynivka, the southernmost point of the belt, Russian forces now occupy the east side of the city, while the western side across the Kryvyi Torets river has become a kill zone.
The advance has come at a huge cost in lives.
For Ukrainian civilians, the cost has also been heavy. In Sloviansk and Kramatorsk, factories and apartment buildings show evidence of daily strikes.
Petrol stations are netted, fuel pumps sandbagged, with concrete shelters for staff and customers. When FPV drones appear multiple times each day, a continuous siren reverberates.
In Kramatorsk, after a basement meeting with Krutkov, the Guardian encountered the aftermath of a Shahed drone strike on an apartment building that injured four people.
Yulia Melnyk, 46, who lives in the building, was fatalistic as she tidied her flat. "Sometimes the noise scares me.
But if I'm hearing the explosion, I'm alive and life goes on," she said.
