Ukrainian forces have decisively breached Russia’s first defensive line near Zaporizhzhia after weeks of painstaking mine clearance, and expect faster gains as they press the weaker second line, the general leading the southern counteroffensive has said. Brig Gen Oleksandr Tarnavskiy estimated Russia had devoted 60% of its time and resources into building the first defensive line and only 20% each into the second and third lines because Moscow had not expected Ukrainian forces to get through. “We are now between the first and second defensive lines,” he said, speaking to the Observer in his first interview since the breakthrough. Ukrainian forces were now pushing out on both sides of the breach and consolidating their hold on territory seized in recent fighting, he said. “In the centre of the offensive, we are now completing the destruction of enemy units that provide cover for the retreat of Russian troops behind their second defensive line.” A vast minefield trapped Ukrainian troops for weeks as infantry sappers slowly cleared an assault route on foot. Russian troops behind it “just stood and waited for the Ukrainian army”, picking off vehicles with shells and drones, he said. But now that barrier has been crossed, Russians have been forced into manoeuvres and Ukrainians are back in their tanks and other armoured vehicles. In a sign that Moscow is feeling the pressure, it has redeployed troops to the area from frontlines inside occupied Ukraine – Kherson to the west and Lyman to the north-east – and also from inside Russia, he said. “The enemy is pulling up reserves, not only from Ukraine but also from Russia. But sooner or later, the Russians will run out of all the best soldiers. This will give us an impetus to attack more and faster,” Tarnavskiy said. “Everything is ahead of us.” A tank specialist by training, Tarnavskiy has built up an impressive track record fighting Russian troops since they crossed the border in 2022. Last September, he was made commander of the troops fighting to liberate Kherson; two months later the city was liberated. There were hopes for similar rapid progress in the summer counteroffensive, which aims to push down towards the Sea of Azov, cutting off Russian troops in Kherson and occupied Crimea from other forces and severing their supply lines. Instead, it stalled for months, with casualties mounting but frontlines apparently static, feeding discontent and criticism in western capitals that had provided weapons and training. Tarnavskiy shrugged off that criticism, saying he preferred to judge a job when finished and thanking the UK and other allies for their support in training and weapons, including Challenger tanks that are already in the field. “When we started the counteroffensive ... we spent more time than we expected on de-mining the territories,” he admitted. “Unfortunately, the evacuation of the wounded was difficult for us. And this also complicated our advance. “In my opinion, the Russians believed the Ukrainians would not get through this line of defence. They had been preparing for over one year. They did everything to make sure that this area was prepared well.” Russian troops were ensconced in concrete dugouts behind anti-tank traps and beyond a minefield so packed with explosives, and so exposed, that any vehicles – de-mining or assault – that approached the area were shelled heavily from fixed, reinforced positions, he said. But Ukrainians, who have repeatedly surprised the world in their success against Russian military might, pressed forward. Infantry forces went out at night to painstakingly clear a corridor through the mines, moving metre by metre in the dark. “As soon as any equipment appeared there, the Russians immediately began to fire at it and destroy it. That’s why de-mining was carried out only by infantry and only at night.” Now that the minefield has been breached, Russians have lost much of their advantage. “There is a very big difference between the first and second line of defence,” said Tarnavskiy. The second line is not as well built, so Ukrainians can use their vehicles, although there are still minefields. Because Russian forces are also operating in this area, they are in patches rather than a single defensive cordon. When asked about slow progress breaking through Russian lines in another offensive further east along the enemy’s defensive line, he said it had other aims and added that Ukraine was preparing other surprise offensives to drain Moscow’s forces. “To be successful in one direction, you always need to mislead the enemy. The main goal of the [offensive near the] village of Velyka Novosilka had a different aim,” Tarnavskiy said. He refused to be drawn on timelines for reaching big targets such as Melitopol, or the coastline for the Sea of Azov, but said fighting would continue. Slow military progress over the summer bolstered those in western capitals calling for negotiations with Vladimir Putin to end the war. That position has been fiercely rejected in Ukraine, where many feel only total defeat of Russia will forestall another invasion; any settlement that rewarded Moscow for use of force would give it reason to try again in future. “If we stop advancing, the enemy will gather new forces and strengthen. We will reach the 1991 borders of Ukraine ... We don’t want to see our kids and even our grandkids fighting against Russians, and who is there to stop them? Only us.” Tarnavskiy is commander of the Tavria operational and strategic group of forces, named after the historic region that included Crimea, a reminder of Ukraine’s military commitments, now sharpened by the losses of the last 18 months. “The closer to victory, the harder it is. Why? Because, unfortunately, we are losing the strongest and best. So now we have to concentrate on certain areas and finish the job. No matter how hard it is for all of us.”