The Battle for a Hilltop Fortress in Eastern Ukraine, Explained

Russian forces have razed dozens of towns and cities in Ukraine over the past 26 months — killing thousands of civilians, forcing millions from their homes and leaving a trail of destruction that is impossible to calculate.

Sievierodonetsk. Bakhmut. Avdiivka. Cities and towns little known to the world have become the scorched-earth battlegrounds where two armies clashed for months to bloody effect before the Russians finally prevailed.

Now Russian forces have set their sight on Chasiv Yar, a hilltop fortress town in eastern Ukraine. The campaign is part of an intense effort by Russia to achieve what could be its most operationally significant advance since the first summer of the war in 2022.

Chasiv Yar covers only about five square miles, but if the Russians can seize it they will control commanding heights that will allow them to directly target the main agglomeration of cities still under Kyiv’s control in the Donetsk region. That includes the headquarters of the Ukrainian eastern command in Kramatorsk.

It would also put Russian troops within around 10 miles of Kostiantynivka, the main supply juncture for Ukrainian forces across much of the eastern front.

Chasiv Yar is the “key” that “will open the gate for exhaustive and long-lasting battles,” said Serhiy Hrabsky, a military analyst who is a former colonel in the Ukrainian Army.

While Ukraine hopes renewed military assistance from the United States will allow it to start stabilizing fraying defensive lines, its soldiers are desperately short of just about everything — from artillery shells and tank rounds to air defenses and armored vehicles.

It could take weeks for significant flows of matériel to change the dynamic on the front, and Ukrainian officials have warned that the Kremlin will try to exploit this window of opportunity to target Ukrainian defenses wherever it can.

Just this week, Russian forces exploited a gap in Ukrainian defenses outside Avdiivka to advanced about two miles on the village of Ocheretyne, which is 30 miles south of Chasiv Yar, according to the Ukrainian military.

President Volodymyr Zelensky said he believed that Russia was planning to capture Chasiv Yar by May 9 — a national holiday in Russia commemorating the Soviet Union’s victory over Nazi Germany.

As Russia targets Chasiv Yar, here is a look at how the battle is unfolding, where the fighting stands and why the loss of the town would present new challenges for Ukraine.

What is the situation in Chasiv Yar?

During a visit to Chasiv Yar a year ago, as the battle for Bakhmut reached its bloody denouement just six miles to the east, it was clear the once-bucolic town in the heart of the eastern Donbas region had already been largely transformed into a military garrison.

Most of the about 13,000 residents had fled as shelling rattled largely empty apartment buildings and craters dotted the tree-lined roads.

After Bakhmut fell to Russia, Ukraine used Chasiv Yar to direct fire at Russian forces from across the open plains that surrounded it. They also used the town as a staging point for assaults aimed at reclaiming some villages around Bakhmut.

But as American assistance slowed and then largely stopped this year, the Russians took back much of what they lost around Bakhmut and began to push across the mined plains between Bakhmut and Chasiv Yar in one bloody assault after another.

The Russians have established a foothold in a forest belt near the eastern edge of the city, according to both sides.

They are also trying to flank Ukrainian forces by attacking through the villages of Bohdanivka, to the north, and Ivanivske, to the south, said Nazar Voloshyn, the Ukrainian military spokesman for the area.

Around 20,000 to 25,000 Russian soldiers are engaged in the offensive, he said, and assaults continue “around the clock.”

“We respond with FPV drones, but it’s not enough,” said Private Oksana, a drone operator fighting in Chasiv Yar who was reached by phone and who used only her first name in accordance will military protocol. She was referring to the first-person viewpoint drones that Ukraine has increasingly had to rely on to slow Russian advances as its deficit of artillery shells has deepened.

“The tactical situation is quite dynamic, challenging and constantly changing,” Mr. Voloshyn, the military spokesman, said in response to written questions. But Ukrainian troops are being reinforced and the defense is holding, he said.

Despite the relentless attacks, the Ukrainian defenders have some advantages, Mr. Hrabsky, the military analyst, said.

The Donbas canal, which cuts a path dividing a small residential district on the eastern edge of town from the rest of Chasiv Yar, adds a natural barrier that could slow the Russian advance. And Mr. Hrabsky said the Ukrainians have had years to construct strong fortifications in and around the town.

How has Russia used its air power?

Russia has used its increasing dominance in the air to smash nearly every standing structure into ruins and destroy those fortifications.

In recent months, as Ukrainian air defenses have been depleted, Russian pilots have grown more bold in flying sorties near the front and Moscow is using its tactical aviation advantage to devastating effect.

The British military intelligence agency said this week that the “concerted aerial bombardment” of Chasiv Yar was “a tactic repeated from the Avdiivka campaign,” in which Russian warplanes paved the way for infantry assaults and the fall of the Ukrainian stronghold in February.

The Ukrainian Air Force said Russian planes were dropping as many as two dozen bombs loaded with more than 1,000 pounds of explosives on Chasiv Yar every day.

“In just the past day, 100 mortar and artillery bombardments were recorded on this direction, which is twice as many compared to the previous day,” Mr. Voloshyn said on Tuesday.

Col. Mart Vendla, deputy head of the Estonian Defense Forces Headquarters, said this week that Ukraine’s loss of Avdiivka and the Russians advance on Chasiv Yar “clearly has to do with ammunition shortages and the Russian side’s preparedness to risk using tactical air power again.”

What if Chasiv Yar falls?

Mr. Hrabsky said that it was impossible to predict how the battle would play out.

While the Ukrainians cannot match Russian firepower and Moscow remains willing to throw countless soldiers into the fight, the fact that Ukrainian commanders know more supplies are coming might allow them to dip into reserves and resist the onslaught.

The stakes are high for both sides.

The cities that lie beyond Chasiv Yar are not just important defensive bastions. They are home to hundreds of thousands of civilians, many of whom work in the industries that play an important role in Ukraine’s domestic arms production.

If Chasiv Yar falls, some of those population centers will be within reach of Russian artillery. Russia has demonstrated time and again what it can do when a settlement falls within reach of its big guns — destroy local industries, savage critical infrastructure and render once peaceful towns unsuitable for human life.

Controlling Chasiv Yar would also put Kostiantynivka, the main supply node for Ukrainian forces in the east that is only a few miles down the road, within striking distance of Russian forces.

The railway in Kostiantynivka is “the backbone of Ukrainian supply and support” in the east, Mr. Hrabsky said. This year, the Russians hit the main station with missiles, but the trains are still running.

Sergei K. Shoigu, the Russian defense minister, said on Tuesday that Russia would intensify strikes against Ukrainian logistical centers and storage facilities as it tried to slow the movement of critical Western military aid to the front.

But even if Chasiv Yar falls, military analysts said, the battles that follow will most likely be long, brutal affairs that play out over months.

“We cannot give up,” Private Oksana said, “because of those who have already given their lives in defense of our land.”

Liubov Sholudko contributed reporting.