Rammed back into the bushes, out past destroyed Bradleys and ageing Humvees, the Soviet-era T72 lowers its turret to fire. Its targets are Russian positions, imperiled by Ukraine's push south, just past the building over the horizon. Three rounds whistle into the distance, the tank is spotted, and is gone in a swirl of dust.

The frontline near Robotine has been the focus of Ukraine's renewed counteroffensive. And for troops here, the fight has been as tough as it has been to hear critical Western analysis of its pace. They have been dealt a tough hand: taking on a prepared Russian military, with donated NATO equipment that's not always kept at NATO service standards. The Humvee in which CNN was driven to the front -- becoming the first media to reach this part of Ukraine's counteroffensive -- had threadbare tires.

"They are wrong," says Vitaly, a tank operator from the 15th National Guard, of Western criticism of their progress. "We have success. Sometimes more, sometimes less. It depends on how fortified they (the Russians) are." The Russian troops had a year to get ready, he notes, adding: "The biggest problem is underestimation of the enemy."

That is less of an issue for the troops here, who must speed past the destroyed US-donated Bradleys that litter the road after their earlier, troubled assaults. During a week spent with troops around the town of Orikhiv, CNN saw a palpable improvement in morale as some advances appeared to be made. All the service members that spoke to CNN are identified by their first names or callsigns only, due to security concerns.

First access to the counteroffensive

Lotos, a tank unit commander, says the telegraphing of the attack's focus in the press did not help. "It won't be as easy as in Kharkiv. Here the enemy was ready, unfortunately. Everybody chatted for months that we would move here." He adds: "We expected less resistance. They are holding. They have leadership. It is not often you say that about the enemy."

Yet the major handicap Ukraine faces in this already difficult fight is palpable in the cratered streets of Orikhiv. Russian air superiority is taking Ukrainian lives daily, with half-ton bombs landing frequently -- sometimes 20 in as many minutes.

Beyond the view of Ukraine's armchair critics is a fast-trained, motivated army being asked to use Western donations to achieve a swift breakthrough against a Russian army that has had a year to lay minefields and fortifications -- a difficult feat at the best of times. But Kyiv has one extra handicap. It is attempting this without something NATO militaries would insist on: air superiority. Ukraine's air force is smaller, and NATO has yet to deliver F-16s, meaning that the threat of a Russian Su-35 overhead often forces troops here to head to the bunkers.

Life underground is nerve-shredding. A Russian rocket -- or guided glide bomb -- could hit at any time, and they have been showing some accuracy, says one Ukrainian soldier. Ukrainian troops constantly relocate and hide their vehicles at every opportunity to frustrate Russian targeting.

Still, vast destruction has plagued Orikhiv's main buildings. The "invincibility point," a converted school where the few remaining civilians received handout food and could wash, was hit in June, killing five. That building and several nearby are leveled, and smoke from another blast that morning still smolders. The smell of death haunted one apartment block that was torn through by a missile. Some streets of the town smell of explosives. Military casualties are not declared.

Among the most closely hunted of Ukraine's forces are Orikhiv's military medics, whose lives are spent mostly underground, their last two triage points bombed. Their bunker is where they wait, nocturnal even in the day, a cardboard Sharpie sign saying "Night club" on the wall. Only dark humor fits here and death is close enough to be shrugged off.

"When they hit further than 100 meters away from us we don't pay attention," says one medic, Eugene. "If it's closer we just laugh hysterically."

His colleague Vlad adds: "I tell everybody, we will all die. But a bit later. Maybe in 50 years."

Thirst for revenge

Disrupting casualty evacuations appears to them to be a Russian priority. "The Russians let the ambulance get to the casualty," Eugene says. "But as soon as we load them, they unleash everything on us. Anti-tank rockets, grenade launchers, mortars. We lost five wheels on our APC during two days of the assault."

Eugene adds that they rarely treat casualties at the collection point. "We do everything inside (the ambulance) at high speed. And the road isn't the best one. What was our speed record? 180 km an hour."

After months of headlines about Russian incompetence and disarray, they are learning that Moscow's better troops -- the paratroopers on the southern frontlines -- have not forgotten their training. "You shouldn't honor the enemy," says Vlad. "But don't underestimate him."

There is little danger of that in this team, who lost a colleague on Friday to artillery fire during an operation. Andrei, aged 33, was hit when traveling in his car. They buried him Monday.

The men linger in a silent gaze when they talk about racing to one of their own. "We went there immediately," says Eugene. "Another team picked up his driver who got lucky. And I got the hardest thing I ever did -- pick up the body and deliver it to the morgue."

Vlad adds: "His family, his mother... They are in temporarily occupied territories. They couldn't even come to the funeral."

At another casualty evacuation point near Orikhiv, shells fly back and forth over the head of another medic, Julia, as she describes their morale. "We are still optimistic but not as we used to be. Assaulting is emotionally easier. It was very hard standing in defense for 18 months."

She says many of the wounded they treat seek to return to the frontline. "They know it's not going be the same -- they won't be in the assault squad. But they want to come back. Because thirst for revenge is very strong. Hatred is very strong."