Tucked into a narrow tree line on Ukraine's southern front, a young Ukrainian soldier wearing an American flag patch talks about how frightening it was the first time his team assaulted the densely mined Russian positions in the offensive launched a month ago.

"The first day was the most difficult," says the 19-year-old who goes by his call sign, "Kach." "We didn't know what to expect, what could happen, how events would unfold."

Nor did anyone really. After months of anticipation, Ukraine finally launched its "Spring Offensive" in early June. Everyone knew it would be tough going for the Ukrainians, having watched Russia dig in and build up formidable defenses over months. But even with no real expectation that the offensive would look like Ukraine's lightening fast advance around Kharkiv last September, the hope among western officials was that Ukraine would be farther along and more successful than they are right now.

But the offensive has proven more challenging than many expected, even with an arsenal of new western weaponry and equipment fueling the assault.

Among the most-anticipated pieces of equipment was the American-made Bradley Fighting Vehicle, a critical addition to help infantry cross the dangerous and open terrain.

Speaking to CNN, Kach is sitting inside his own Bradley. Just a few months ago, Kach was going through an accelerated US training course in Germany, where he and other Ukrainian soldiers were taught a more American, complex and nimble way of fighting.

Kach's brigade, the 47th Mechanized Brigade, is the only one to have received the coveted Bradleys, 200 of which have been committed by the US.

A dog named Bradley

The armored fighting vehicles are so admired by Ukrainian soldiers that running around Kach's team's camp barking is "Bradley" -- the brigade press officer's 6-month-old rescue puppy.

The Velcro flag patch on Kach's chest was a parting gift from his American trainer in Germany, who told him it would bring good luck. But it was the thick armor, powerful machine guns, rockets and night vision capabilities on the Bradley that gave Kach a boost of confidence when ordered to assault the Russians.

When the brigade did, the Russians were ready. Dense minefields had been laid, rows of winding trenches were dug. Russian artillery started to pick off the vehicles sent out to de-mine the area. On top of that, this southern direction of attack was perhaps the most predictable in the offensive: designed to try to punch through the Russian line, drive south and split the southern land bridge connecting Russian-occupied Crimea and Donbas before finally reaching the Sea of Azov.

The 47th ran into trouble very quickly trying to pierce the Russian line in their newly acquired armor. Photos and videos showed charred armored vehicles, including Bradleys and a German Leopard tank. Oryx, a military analysis site based on open source information, reports that around three dozen Bradleys have been destroyed or damaged.

"It's not that hard to clear a minefield but it is very hard to clear a minefield when in doing so under fire and from different types of fire," says Rob Lee, a military analyst who is a senior fellow at the Foreign Policy Research Institute who just visited Ukraine.

"Since the beginning of that campaign, they adapted and it's largely become a dismounted infantry fight," Lee says. "It's extremely arduous, extremely tough. The burden is very heavy on individual infantry men."

There is no disagreement from rank-and-file troops, nor from their commanders, who admit the progress has been slower than they would like.

Clearing mines near the 'Zero Line'

In a southern town about 10 kilometers from the jagged line of contact -- often called the "zero line," the brigade's 25th Separate Assault Battalion has set up a command post in a basement bunker. It's filled with enormous floor-to-ceiling maps denoting Ukrainian and Russian battlefield positions. A large computer monitor tracks the fighting through incoming reports and dozens of drone feeds.

One soldier updating the maps showed CNN a Russian map recently taken from a trench that had been cleared, detailing the Russian defenses in the area. Outside loud booms from Ukrainian artillery cannons sweep across the heavily damaged and now largely empty town.

The drone feeds show the empty fields littered with anti-tank and -personnel mines, pockmarked with craters from artillery. The tree lines on the other side hide Russian forces camped out in trenches.

"We need to break through the mine barriers so that equipment and infantry can pass," says Tral, the commander of a demining -- or "sapping" -- platoon. Moments prior he had just returned to the command post from yet another treacherous mission on foot to destroy or de-fuse the mines blocking their way.

They work slowly, Tral says, "everything is done gradually. Where we have already [cleared] passages, our troops are already entering there. We do not allow [the Russians] to enter where we have already demined the territory."

Tral shares a video from his phone showing a large explosion shooting dirt and shrapnel into the sky after a Russian mine was detonated. (Ukrainian soldiers often ask to go by just one name or their "call sign.")

"It's hard," he says, "very hard."

Another soldier in the basement, Stanislav, keeps his eyes fixed on the big monitor, pulling up different drone feeds from his sector. As he watches Ukrainian artillery shells landing near Russian positions, he will help coordinate between the artillery teams and other forces closer to where the shells land to direct the fire.

"In this war artillery is the most valuable asset," Stanislav says flatly, eying the feed. "There are a lot of Russians. In here and overall. They have more guns, they have more shells and they have more people so we must counter that with our ... professionalism."

These days, that means the slow grind of the exposed troops fighting from trench to trench, assaulting tree line to tree line under heavy fire.

"There are [soldiers] in trenches," Stanislav says. "We can't liberate land with artillery. There are people that are working there."

That work requires resilience and patience. The soldier with the Russian map points to a tree line, spreading his index and middle finger to represent the distance, roughly 300 meters, he says "this section took us one and a half months."

Under a desk is Bradley, the press officer's puppy. When it's time to go, he strains his leash refusing to go back outside because of the artillery firing.