BAKHMUT, Ukraine — Ukrainian soldiers scurried around the howitzer in a field one recent morning. In a flurry of activity, one man lugged a 106-pound explosive shell from a truck to the gun. Another, using a wooden pole, shoved it into the breach.

“Loaded!” the soldier shouted, then knelt on the ground and covered his ears with his hands.

The gun fired with a thunderous boom. A cloud of smoke wafted up. Leaves fluttered down from nearby trees. The shell sailed off toward the Russians with a metallic shriek.

It is a scene repeated thousands of times daily along the frontline in Ukraine: artillery duels and long-range strikes from both sides on targets ranging from infantry to fuel depots to tanks.

And what followed the salvo fired on Wednesday morning in eastern Ukraine was also indicative of the rhythm of this war: a coffee break.

This is a war fought in a cycle of opposites — bursts of chaos from outgoing or incoming shelling, and then long lulls in which soldiers undertake the most routine activities. Fighters who minutes before unleashed destructive weapons with a thunderous roar settled in a grove of oak trees around a picnic table of wooden ammunition boxes, boiling water on a camp stove and pouring cups of instant coffee.

They rested in an oak forest, overlooking a field of tall green grass and purple flowering thistles. Elsewhere, soldiers used a lull to smoke or get a haircut.

On a recent visit, soldiers from the 58th Brigade fighting in and around the city of Bakhmut, where the artillery war is raging, were both attacking and under attack from artillery.

All about on the rolling, grassy hills west of Bakhmut, puffs of brown smoke rose from incoming Russian strikes, aimed at Ukraine’s artillery positions.

The pivotal importance of long-range fire was one reason the United States and other allies rushed NATO-caliber howitzers to Ukraine. Its military is close to depleting the entire stock of Soviet-legacy shells in its own arsenal and from allied countries in Eastern Europe, and it is now shifting to more abundant NATO ammunition.

Russia has vast supplies of artillery ammunition but indications are surfacing that it is dipping into older reserves that more frequently do not detonate on impact.

The Soviet-legacy howitzer the Ukrainian team fires, a model called the D-20 that is nicknamed the “fishing lure,” has held up well, said the commander, Lieutenant Oleksandr Shakin. American-provided long-range weaponry such as the M777 howitzer and the High Mobility Artillery Rocket System, known as HIMARS, have extended the reach of Ukraine’s army, but the bulk of the arsenal is still Soviet-era guns.

The cannon they fired was made in 1979, he said, and most of the shells were from the 1980s. Still, Lt. Shakin said, “They have not let me down yet.’’

Typically, he said, he fires around 20 shells a day from each gun, conserving Ukraine’s dwindling supply of 152 millimeter ammunition.

“We have a lot of motivation,” said Captain Kostyantin Viter, an artillery officer. “In front of us are our infantry and we have to cover them. Behind us are our families.”

Inside the city of Bakhmut on Wednesday, at a position where soldiers of the 58th Brigade are garrisoned in an abandoned municipal building, the whistles of their colleagues’ shells could be heard sailing overhead — aimed at Russian forces to the east of town.

The soldiers stood in a courtyard, smoking and listening to the whizzing of shells overhead and thuds of explosions in the distance.

The buzzing of electric clippers filled the air, too, as one soldier gave another a haircut. A few trucks were parked in the yard and a dozen or so soldiers milled about.

Half an hour or so on, a new noise joined the background of distant booms: the clang of nearby explosions. What had been a languid summer morning became a scene of chaos.

Soldiers dashed for cover or dove to the ground. After a dozen or so booms, it was over. An acrid smoke wafted over the courtyard, and shards of glass lay about. “Is everybody alive?” a soldier shouted.

All of the soldiers who had been in the yard escaped unhurt. But the Russian rocket strike killed seven civilians and wounded six others in the neighborhood near the soldiers’ base, the authorities reported later.