There is a strange ritual to artillery fire. The most important thing is the camouflage. When properly wrapped up in foliage, the muzzles of howitzers look like fungi. Then there are the messages to be written on shells.
On Thursday, it was "for Zaporizhzhia", where Russian missiles had wreaked carnage in the morning.
A battery commander scribbles calculations on a pad of paper and barks the countdown to fire.
The howitzers belch yellow flames. There is a pause of a few minutes while whoever called in the strike assesses the damage, then another salvo.
In the interim, a cacophony of automatic fire erupts on the other side of the wood - a Russian drone has been spotted. Rather than taking cover, the gunners ignore it.
Their confidence is a mark of how profoundly the tide of this war has changed.
Back in May, these men from Ukraine's 14th mechanised brigade were struggling to hold back Russia's relentless offensive in Donbas, trying to answer an enemy firing five or seven times more shells than they could.
But last month, they took part in the offensive that liberated the Kharkiv region. Now they have crossed the strategic Oskil river and are firing in support of an imminent battle to liberate neighbouring Luhansk oblast.
Now it is the Russians struggling to respond. The target of this strike was "a group of Russian infantry - a bunch of f----ts, to use the technical term", said Denis, the officer commanding, who asks for his surname to be withheld.
But Denis, a career artillery man, mixes his disdain for the enemy with a grudging professional respect for his Russian opposite numbers.
"If I was giving them marks out of five, they'd get a four-plus," he said. "They're working on their own kit and we are getting to grips with different modern things."
AND
This battery, like most of the Ukrainian army, has yet to benefit from high-profile Western deliveries. Their guns are still self-propelled 122mm SAU's - Soviet-built weapons which the men wryly declare were "born in 1970". Denis does not hide his desire for modern replacements.
The Russian artillery set the tone for the first half of the war, battering cities like Mariupol into submission and blasting a path through Donbas for Vladimir Putin's tanks and infantry.
But the balance of power on the battlefield has changed decisively.
When the Russians were routed in Kharkiv at the beginning of last month, their generals withdrew behind the Oskil river to establish a new defensive line. On the map, it was a good move.
But within days, the Ukrainians had forced a crossing and were pushing the Russians back again.
The speed and violence of the battle for Oskil is still evident. At one crossing, a hamlet has been reduced to a group of craters where the smell of burnt tanks and plastic is mixed with the stench of decaying human flesh.
Across the river, total destruction gives way to evidence of chaotic retreat. Abandoned and destroyed armoured vehicles bearing the letter Z still stand on the roadsides.
Two corpses, one in green military fatigues, the other in blue trousers that might have been a policeman's uniform, lie decomposing nearby.
Today the bridgehead is 24km deep in places, and growing daily.
In the coming days and weeks, Russian and Ukrainian commentators agree, it will provide the springboard for an assault on the key town of Svatove in Luhansk.
And despite Putin's promises of mobilised reinforcements, the Russians seem to be short of ammunition.
"They are concentrating on our infantry at the moment, trying to hold back the offensive. And that means they're not often answering," said Valentin, 47.
"At the absolute minimum, we are now on par with them," he added. "But we are probably outgunning them."
"If before the Russians would dump everything to burn up a whole forest or field, now they are being more sparing. They are trying to hit specific targets," added David, a 24-year-old history graduate in the same unit.
"When you see on the news that a Russian ammunition dump has been hit, about two days later they stop firing. So they seem to be able to gather enough somehow to keep firing for two days, then they run out," he added.
These days the Russians are sending over only one or two drones a day - another sign they are running short, he guesses. They have not vanished, however, and remain a deadly threat.
For the gunners, the rapid advance means constant relocation, repeated digging of fresh trenches and attention to camouflage.
Bed is a sleeping bag under a tarpaulin tied to the side of an armoured vehicle. Thursday was fine but the floors of their hastily dug blindages quickly turn into quagmires when it rains.
There are benefits to fighting in autumn, however. It is high mushroom season, and their current woodland billet is full of them. The men have stacked large species called belyanki next to their campfire.
In the woods, the men fry them over a fire, and back in the kitchen at the house serving as battalion headquarters, they turn them into soup and an exceptional casserole.
It is worth enjoying the fruits of autumn while they can, says Denis. No one is looking forward to winter in the field. Far away, yellow sparks fly into the sky - a Himars launch, destined for some target in the Russian rear.
Meanwhile, birds arc over a grain elevator, presumably enjoying the feast laid out when the shelling cracked open the concrete towers.
At a nearby pig farm, the livestock have escaped their pens and are happily rooting around the yards.
The birds and the animals are making the most of a landscape suddenly stripped of human life.
At the current rate of advance, soon even the soldiers may be gone - marching east to dig into a new wood.
"The Russians are not like the Russians we were fighting on Feb 24," said David. "They're not as brave."