KHARKIV, Ukraine (AP) — During pitched battles with far better-armed Russian forces, Ukrainian soldier Batyar’s unit has few options.

Devastating Russian aerial glide bombs that can drop up to 1.5 tons of explosives out of range of most of Ukraine's air defenses are gnawing away at his men’s positions in a new tactic.

Yet, to retreat carries no promise of safety — the rear defensive lines meant to give them cover barely exist, he said.

Lack of ammunition is forcing the outnumbered Ukrainian soldiers to pull back, one village after another, including , as intense fighting roils the countryside surrounding Avdiivka nearly three months after the strategic city .

“It's necessary to increase the pace of building fortifications … so that when we retreat, we will retreat to a prepared position," said Batyar, a unit commander who gave only his military call sign in line with brigade protocols. "These fortifications are not enough.”

Facing an outcry after Avdiivka's fall, Ukraine is rushing to build concrete-fortified trenches, foxholes, firing positions and other barricades on the front lines. But relentless Russian shelling, lack of equipment and crippling bureaucracy plague construction across the vast 1,000-kilometer (600-mile) front, even as a new , according to a dozen Ukrainian soldiers, government officials and construction company directors interviewed by The Associated Press.

The much awaited passed by the U.S. Congress last month is expected to help Ukraine close the firepower gap. But until replenishments arrive, which could take weeks, Russia will continue to exploit Ukraine's weaknesses.

DIG AND FIGHT

Ukraine has allocated nearly 38 billion hryvnias ($960 million) to build an extensive fortification network this year. Soldiers across the front line maintain that should have happened last year, when Ukraine had the upper hand in the fighting, not in the heat of battle now.

Besides trenches and other barricades, the layered system includes mines and anti-tank obstacles known as “dragon's teeth,” normally built in advance of fighting. Russia's preparedness paid off during Kyiv’s failed counteroffensive last summer: Ukraine’s momentum was slowed in the Zaporizhzhia region by Moscow’s extensive fortifications.

But Ukraine was slow to follow suit; it was not until this spring, when weather conditions improved, that any real progress was made. In March, President Volodymyr Zelenskyy announced Ukraine was building 2,000 kilometers (1,240 miles) of fortifications across three lines of defense.

“There was an absence of responsibility. ... People didn't understand that fortifications can save your life if you do it in advance," said Oleksandr, a deputy infantry commander with the 47th brigade in the Avdiivka area who gave only his first name in line with military rules.

"Many people thought we ... wouldn't need to prepare such lines. They didn't expect a new Russian offensive.”

Unlike Russia, Ukraine does not have the option of forcing thousands of . That means Ukrainian soldiers on the front lines must both fight and dig their own trenches.

“It's very hard to do both,” Oleksandr said.

Building the second line, 2 to 5 kilometers behind the front line and within range of Russian artillery, is the responsibility of Ukraine’s poorly-resourced engineering force. The third line, at a greater distance from battle, is constructed by companies under military contracts.

The reasons for Ukraine's lack of preparedness are rooted in the years after independence when it began downsizing its military because it couldn't afford to maintain the large force inherited from the Soviet Union. Its engineering regiments were dismantled until there were only a handful left. Equipment, including excavators and plows so direly needed now, were sold off.

“We entered the war with nothing,” said a serviceman in Ukraine’s engineering force, who spoke on condition of anonymity to talk openly about the lack of preparation. When he arrived to build fortifications in Ukraine’s east in October, all his unit had were aging equipment from the 1960s and shovels, he said.

“Accordingly, that’s the kind of trenches we made.”

DISCONNECTED PITS

Ukraine's lack of adequate defensive lines has helped Russia make significant military gains, and constant enemy fire hinders building.

Five commanders in Avdiivka and Chasiv Yar, which have been under , said without well-prepared positions they were unable to gain a foothold in unfamiliar terrain and defend without suffering huge losses.

In , a strategic hilltop town in Donetsk, the lack of fortifications helped turn the tables in Russia’s favor.

In mid-March, Ukraine’s 67th brigade was rotated in to hold positions roughly 3 kilometers from the town. “I would be hard-pressed to describe them as 'positions,'” said a Ukrainian serviceman who spoke on condition of anonymity to discuss the failings candidly.

He expected dugouts, a labyrinth of trenches and firing positions, but what he found were a series of pits, barely large enough to hide in during artillery barrages.

Under fire, “soldiers would climb out of pits and start digging in each other’s direction so that there is at least some connection between them,” he said. The soil was so sandy that whenever shells struck, the trenches they dug crumbled.

With nowhere to take cover and no means to match the Russian barrages, they retreated 2 kilometers back. Over 100 Ukrainian soldiers were killed or are missing, he said.

“We lost department commanders, platoon commanders, company commanders and sergeants,” he said. “That is, we lost the entire skeleton of the brigade.”

The unit's withdrawal in early April led to it being disbanded by Ukraine’s General Staff. The brigade was blamed for the loss, but commanders said they never had the resources to succeed.

TIME, MONEY, PRESSURE

To rush building across the third line, construction companies were awarded contracts without the usual bidding process.

“There was no time,” said Kharkiv Gov. Oleh Syniehubov.

The move speeded things up but raised concerns of potential corruption — a worry Syniehubov asserted was overstated. “Believe me, we have so many checks-and-balances and government agencies overseeing the building, it is impossible to steal something,” he said.

Finding companies willing to take the risk was another challenge. They faced layers of bureaucracy to get paid, while coming under enormous pressure to work fast.

A contractor in the Sumy region said he had to follow up with a half-dozen government officials to get funding.

“Not many people are willing to do this,” said a construction company director in the Marinka area of the Donetsk region. All the fortifications he is contracted to build should have been erected in 2014, when Russia first invaded Ukraine, he said.

"This is is all a big question for our leadership: Why didn’t they purchase the equipment that military engineers needed to do their jobs? Why did they wait until they just gave it to us?” said the director, who like other company officials spoke on condition of anonymity to discuss sensitive military contracts.

The owner of another company supplying concrete for front-line fortifications said some regional officials, under pressure to build them quickly, were inflating progress. “I saw the figures, and knowing what I know about the supplies, I know they can't be true,” he said.

And then, there are the Russian attacks. Drones monitor building activity as far back as the third line and routinely attack workers.

In Kharkiv, at least four construction workers were killed in the last month, according to the governor. In addition, 10 pieces of equipment were destroyed.

“The enemy sees everything,” he said.

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AP journalist Volodymyr Yurchuk contributed to this report.

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