"It can be said that the Russians' spring and summer campaign has effectively been disrupted," Oleksandr Syrskyi told reporters in a review of the battlefield situation.
Russia has been making incremental gains across several parts of the front line after large-scale deployment of reconnaissance and attack drones prevented quick progress of the sort seen in 2022.
Ukraine says the small advances are coming at a high human cost.
Both sides in the war only rarely discuss casualties, but some Western intelligence estimates put the number of killed and wounded in Ukraine at more than one million.
Syrskyi said the active front line was now 1250km long, and that an estimated 712,000 Russian personnel were involved in the fighting in Ukraine.
Syrskyi said Russian plans to create a "buffer zone" in Sumy and Kharkiv regions in the north and northeast, to take the city of Pokrovsk and to capture all of Donetsk region, had failed.
The capture of all of Donetsk is a key aim of the war for Russia, which controls more than 70 per cent of the region.
Syrskyi said that since the beginning of summer the Russians had been attacking with a tactic that he called "a thousand cuts" - a high number of tiny infantry assaults.
"This consists of the simultaneous use of a large number of small assault groups - four to six servicemen who advance using the terrain, ravines and wooded areas, with the main aim of penetrating as deeply as possible into our territory."
Speaking about a Russian breakthrough in August near the Donetsk town of Dobropillia, Syrskyi said Ukraine had cut off Russian forces along the Kazenyi Torets river in what he called a "trap".
The commander said that in the past two months, Ukraine had hit 85 military or military-industrial facilities on Russian territory, including air bases, depots and factories.
This week, US President Donald Trump suddenly changed his view of the war from one where he said Kyiv had no cards to play to one where Ukraine could take back all of the ground it has lost so far - roughly 20 per cent of its total territory.
He did not, however, offer substantial new assistance to Ukraine to achieve these goals and has shifted the onus on to European allies.
Russia says it is advancing in Ukraine and that Kyiv would be best advised to negotiate peace sooner rather than later.Â
Ukraine has rejected Russia's terms for negotiations, saying they would amount to surrender.
