POKROVSK, Ukraine — Russia’s nearly three-month-old invasion of neighboring Ukraine was punctuated by flawed planning, poor intelligence, barbarism and wanton destruction. But the daily fighting obscures the geographical reality that Russia has made gains on the ground.

Russia’s Defense Ministry said on Tuesday that its forces in eastern Ukraine had advanced to the border between Donetsk and Luhansk, the two Russian-speaking provinces where Moscow-backed separatists have been fighting the Ukrainian military for eight years. .

The ministry’s claim, if confirmed, bolsters the prospect that Russia could soon gain full control of the region, known as Donbas, from just a third before the February 24 invasion.

This is a far cry from what appeared to be the grand ambitions of Russian President Vladimir V. Putin when he launched the invasion: the quick and easy seizure of large swathes of Ukraine, including the capital, kyiv, the overthrow of a hostile government and a replacement with unquestioned loyalty that would ensure Ukraine’s submission.

Nevertheless, the seizure of Donbass, combined with the early success of the Russian invasion in seizing parts of southern Ukraine adjoining the Crimean peninsula, which Russia illegally annexed in 2014, gives the Kremlin enormous leverage in any future negotiation to end the conflict.

Credit…Mauricio Lima for the New York Times

And the Russians have the added advantage of naval dominance in the Black Sea, Ukraine’s only maritime trade route, which they have crippled with an embargo that could eventually starve Ukraine economically and is already contributing to a global grain shortage. .

Testifying before the Senate Armed Services Committee in Washington on Tuesday, Avril D. Haines, the director of national intelligence, warned of a “protracted conflict” in Ukraine as Russia seeks to expand its territorial gains beyond the Donbass region, including the creation of a land bridge on the Ukrainian Black Sea coast.

But Ms Haines warned that Mr Putin would struggle to make those gains without a large-scale mobilization or project, which he seems reluctant to order at the moment. As Mr Putin’s territorial ambitions clash with the limited capabilities of his military, Ms Haines said the war could enter “a more unpredictable and potentially escalating trajectory” over the coming months, increasing the likelihood that Mr Putin makes direct threats against using nuclear weapons.

Over the past few weeks, Ukrainian and Russian troops have engaged in grueling attrition, often fighting bitterly over small areas as a village falls to the Russians one day only to be recaptured by the Ukrainians days later. late.

Ukrainians are increasingly dependent on an injection of Western military and humanitarian aid, much of it from the United States, where the House was voting Tuesday night to approve a nearly $40 billion emergency plan.

“The Russians aren’t winning, and the Ukrainians aren’t winning, and we’re kind of at an impasse here,” said Lt. Gen. Scott D. Berrier, director of the Pentagon’s Defense Intelligence Agency, who testified alongside of Mrs. Haines.

Credit…Pete Marovich for The New York Times

Yet Russia has almost achieved one of its main objectives: to seize a land bridge connecting Russian territory to the Crimean peninsula.

When Mr Putin ordered the invasion, some of his army’s most skilled fighters left Crimea and southern Russia, quickly seizing a sliver of Ukrainian territory along the Sea of ​​Azov. The last bastion of Ukrainian resistance in this region, at the Azovstal ironworks in Mariupol, has been reduced to a few hundred starving soldiers, now mostly confined to bunkers.

But efforts by Russian forces to expand and fortify the land bridge have been complicated by Ukrainian forces deployed along an east-west front that ripples through vast fields of wheat and sometimes engulfs villages and towns.

Although Russian artillery and rockets wreaked havoc in residential areas, leveling homes and terrorizing residents, the Russian military did not commit enough forces to move the line significantly or threaten the main center industrialist in Zaporizhzhia, the largest city near the frontline, Colonel Oleg Goncharuk, the commander of the 128th Separate Mountain Assault Brigade, said in an interview last month.

Credit…Lynsey Addario for The New York Times

“They will try to prevent our forces from advancing and they are trying to consolidate their positions,” said Colonel Goncharuk, whose forces are deployed along the southeastern front. “But we don’t know their orders or what their ambitions are.”

The fighting is fiercest in the eastern provinces of Donetsk and Luhansk.

At the main hospital in Kramatorsk, a town in Donetsk, ambulances are pouring in day and night, carrying wounded soldiers from the front, who say they are pinned down by near-constant shelling.

About 80% of patients are injured by explosives such as mines and artillery shells, said Captain Eduard Antonovskyy, deputy commander of the hospital’s medical unit. For this reason, he said, very few patients have serious injuries. Either you’re far enough from an explosion to survive or you’re not, he said.

“We either get moderate injuries or fatalities,” captain Antonovskyy said.

Russian forces now control about 80% of Donbass, according to Ukrainian officials, and have focused their efforts on a pocket of Ukrainian-held territory with Kramatorsk at its center.

Credit…Lynsey Addario for The New York Times

All around the city, the booms of distant battles are heard at all hours and thick smoke hangs like a morning fog. Almost daily, Russian forces launch rocket attacks and airstrikes on the city itself, but the most punitive violence is reserved for places within range of Russian artillery.

About 100 km northeast of Kramatorsk is Severodonetsk, where Russian artillery, parked about five or six miles outside the city, rarely gives way, making it difficult for the approximately 15,000 residents who remain to venture above ground.

Oleg Grigorov, the Luhansk region’s police chief, compared the violence to the Battle of Stalingrad in World War II, when Soviet forces turned the tide against the Nazis, but only after suffering huge casualties .

“It never ends. At all,” Mr. Grigorov said. “Entire neighborhoods are destroyed. For days, weeks, they bombard. They intentionally destroy our infrastructure and the civilian population.

Mr Grigorov said around 200 of his officers remained in the town, which lost electricity and water. Their main task is to deliver food to people sheltering in their basements and to bury the dead.

The Russian blockade of Ukraine by the Black Sea has not diminished the Kremlin’s desire to take control of Odessa, the most important Ukrainian port, which has been the target of several air attacks. Recently, Russian forces fired seven missiles, hitting a shopping mall and a consumer goods warehouse and killing at least one person and injuring several others, Ukrainian officials said.

The strike came just hours after European Council President Charles Michel traveled to Odessa, where he was forced to take refuge in a bomb shelter due to another attack.

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Michel, who met Ukrainian Prime Minister Denys Shmyhal, criticized Russia for strangling Ukrainian grain exports that feed people around the world.

“I saw silos full of grain, wheat and corn ready to be exported,” Michel said in a statement. “This badly needed food is blocked because of the Russian war and the blockade of Black Sea ports, with dire consequences for vulnerable countries.”

Ukrainian President Volodymyr Zelensky has urged the international community to pressure Russia to lift the blockade.

“For the first time in decades, there is no usual movement of the merchant fleet, no usual port is functioning in Odessa,” he said in an overnight address. “Probably, this has never happened in Odessa since World War II.”

Ukraine’s economy is expected to contract by 30% this year, the European Bank for Reconstruction and Development said on Tuesday, worsening its forecast from just two months ago, when it predicted a 20% contraction.

The war has “put Ukraine’s economy under enormous pressure, with the heavy devastation of infrastructure and production capacities”, the bank said in an economic update.

He estimated that 30-50% of Ukrainian businesses have closed, 10% of the population has fled the country and another 15% are internally displaced.

The bank also forecast Russia’s economy to contract 10% this year and stagnate next year, with a bleak outlook unless a peace deal leads to an easing of Western sanctions.

Michael Schwirtz reported from Pokrovsk, Ukraine, Marc Santora from Krakow, Poland, and Michael Levenson from New York. The report was provided by Julian E. Barnes and Emily Cochrane of Washington, and Eshe Nelson and Cora Engelbrecht from London.