KYIV, Ukraine (AP) — Russia pressed its offensive in Ukraine’s eastern Donbas region Sunday as Poland’s president traveled to Kyiv to support the country’s Western aspirations and became the first foreign leader to address the Ukrainian parliament since the start of the war.

Ukrainian lawmakers stood to applaud Polish President Andrzej Duda, who thanked them for the honor of speaking in a place where “the heart of a free, independent and democratic Ukraine beats.”

Duda’s visit, his second to Ukraine’s capital since April, came as Russian and Ukrainian forces engaged in battles scattered along a 551-kilometer (342-mile) wedge of the country’s eastern industrial heartland.

After declaring its full control of a sprawling seaside steel plant that was the last defense holdout in the port city of Mariupol, the Russian military launched artillery and missile attacks in Ukraine’s industrial heartland, seeking to expand the territory Moscow-backed separatists have held since 2014.

In a Saturday night video address to the nation, Ukrainian President Volodymyr Zelenskyy described the situation in the Donbas as “really hard,” but he said his country’s ability to withstand nearly three months of full-scale war against Russia “is good news.”

“Every day that our defenders take away from these offensive plans of Russia, disrupting them, is a concrete contribution to the approach of the main day. The desired day that we are all looking forward to and fighting for: Victory Day,” Zelenskyy said.

Zelenskyy stressed Saturday that the 27-member European Union should consider Ukraine’s desire to join the bloc as soon as possible within the context of Russia’s invasion.

“I want to emphasize that our European integration path is not just about politics,” Zelenskyy said. “It’s about quality of life. And about the fact that Ukrainians perceive the values of life in the same way as the vast majority of Europeans.”

Ukraine’s potential EU candidacy is set to be discussed at a Brussels summit in late June. The government in Warsaw is ramping up efforts to persuade other EU members that are more hesitant about accepting the war-ravaged country as a member.

Poland has welcomed millions of Ukrainian refugees and become a gateway for Western humanitarian aid and weapons going into Ukraine. It is also a transit point into Ukraine for some foreign fighters, including from Belarus, who have volunteered to fight against the Russian forces.

“Despite the great destruction, despite the terrible crime and great suffering that the Ukrainian people suffered every day, the Russian invaders did not break you. They failed at it. And I believe deeply that they will never succeed,” he told the Verkhovna Rada, Ukraine’s legislature. “I want to say it with all my might: The free world has the face of Ukraine today.”

Russia appeared to have made slow grinding moves forward in the Donbas in recent days. It intensified efforts to capture Sievierodonetsk, the main city under Ukrainian control in Luhansk province, which together with Donetsk province makes up the Donbas.

Luhansk Gov. Serhii Haidai said the only functioning hospital in the city has just three doctors and enough supplies for 10 days.

On Sunday, the British Ministry of Defense said Russia’s only operational company of BMP-T Terminator tank support vehicles, which are designed to protect main battle tanks, “has likely been deployed to the Sievierodonetsk axis of the Donbas offensive.”

It said, however, with a maximum of 10 of the vehicles deployed, “they are unlikely to have a significant impact on the campaign.”

In a general staff morning report, Russia also said that it was preparing to resume its offensive toward Slovyansk, a city in Donetsk province that is critical to Russia’s objective of capturing all of eastern Ukraine and saw fierce fighting last month after Moscow’s troops backed off from Kyiv.

Russian shelling on Saturday killed seven civilians and injured 10 more elsewhere in Donetsk province, the regional governor said.

A monastery in the village of Bohorodichne was evacuated after being hit by a Russian airstrike, the regional police said Saturday. About 100 monks, nuns and children had been seeking safe shelter in the basement of the church and no one was hurt, the police said in a Facebook post.

With Russia claiming to have taken prisoner nearly 2,500 Ukrainian fighters from the besieged Mariupol steel plant, concerns grew about their fate and the future facing the remaining residents of the city, now in ruins with more than 20,000 residents feared dead.

Family members of the fighters, who came from a variety of military and law enforcement units, have pleaded for them to be given rights as prisoners of war and eventually returned to Ukraine. Deputy Prime Minister Iryna Vereshchuk said Saturday that Ukraine “will fight for the return” of every one of them.

The Russian Defense Ministry on Saturday released video of its troops taking into custody Serhiy Volynskyy, the commander of the Ukrainian Navy’s 36th Special Marine Brigade, which was one of the main forces defending the steel plant. The Associated Press has not been able to independently verify the date, location and conditions of the video.

The Azovstal steel plant for weeks was the last defense holdout in Mariupol and became a symbol of Ukrainian tenacity. Its seizure gave Russian President Vladimir Putin a badly wanted victory in the war he began nearly three months ago.

Denis Pushilin, the pro-Kremlin head of the self-proclaimed Donetsk People’s Republic, vowed the Ukrainian fighters from the plant would face tribunals. He said the fighters included some foreign nationals, though he did not provide details.

The Ukrainian government has not commented on Russia’s claim of capturing Azovstal. Ukraine’s military had told the fighters their mission was complete and they could come out. It described their extraction as an evacuation, not a mass surrender.

Mariupol, which is part of the Donbas, was blockaded early in the war and became a frightening example to people elsewhere in the country of the hunger, terror and death they might face if the Russians surrounded their communities.

The mayor warned Saturday that the city faced a health and sanitation “catastrophe” from mass burials in shallow pits across the ruined city as well as the breakdown of sewage systems. An estimated 100,000 of the 450,000 people who resided in Mariupol before the war remain.

“In addition to the humanitarian catastrophe created by the (Russian) occupiers and collaborators, the city is on the verge of an outbreak of infectious diseases,” Mayor Vadim Boychenko said said on the messaging app Telegram.

With Russia controlling the city, Ukrainian authorities are likely to face delays in documenting evidence of alleged Russian atrocities in Mariupol, including the bombings of a maternity hospital and a theater where hundreds of civilians had taken cover.

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Becatoros reported from Donetsk. Associated Press journalists Yuras Karmanau in Lviv, Andrea Rosa in Kharkiv and other AP staffers around the world contributed.

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Follow AP’s coverage of the war in Ukraine: https://apnews.com/hub/russia-ukraine

WASHINGTON (AP) — The top U.S. military officer challenged the next generation of Army soldiers on Saturday to prepare America’s military to fight future wars that may look little like the wars of today.

Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, painted a grim picture of a world that is becoming more unstable, with great powers intent on changing the global order. He told graduating cadets at the U.S. Military Academy at West Point that they will bear the responsibility to make sure America is ready.

“The world you are being commissioned into has the potential for significant international conflict between great powers. And that potential is increasing, not decreasing,” Milley told the cadets. “Whatever overmatch we, the United States, enjoyed militarily for the last 70 years is closing quickly, and the United States will be, in fact, we already are challenged in every domain of warfare, space, cyber, maritime, air, and of course land.”

America, he said, is no longer the unchallenged global power. Instead, it is being tested in Europe by Russian aggression, in Asia by China’s dramatic economic and military growth as well as North Korea’s nuclear and missile threats, and in the Middle East and Africa by instability from terrorists.

Drawing a parallel with what military officials are seeing in Russia’s war on Ukraine, Milley said future warfare will be highly complex, with elusive enemies and urban warfare that requires long-range precision weapons, and new advanced technologies.

The U.S. has already been rushing new, high-tech drones and other weapons to the Ukrainian military — in some cases equipment that was just in the early prototype phases. Weapons such as the shoulder-launched kamikaze Switchblade drones are being used against the Russians, even as they are still evolving.

And as the war in Ukraine has shifted — from Russia’s unsuccessful battle to take Kyiv to a gritty urban battle for towns in the eastern Donbas region — so has the need for different types of weapons. Early weeks focused on long-range precision weapons such as Stinger and Javelin missiles, but now the emphasis is on artillery, and increased shipments of howitzers.

And over the next 25 to 30 years, the fundamental character of war and its weapons will continue to change.

The U.S. military, Milley said, can’t cling to concepts and weapons of old, but must urgently modernize and develop the force and equipment that can deter or, if needed, win in a global conflict. And the graduating officers, he said, will have to change the way U.S. forces think, train and fight.

As the Army’s leaders of tomorrow, Milley said, the newly minted 2nd lieutenants will be fighting with robotic tanks, ships and airplanes, and relying on artificial intelligence, synthetic fuels, 3-D manufacturing and human engineering.

“It will be your generation that will carry the burden and shoulder the responsibility to maintain the peace, to contain and to prevent the outbreak of great power war,” he said.

In stark terms, Milley described what failing to prevent wars between great powers looks like.

“Consider for a moment that 26,000 — 26,000 — soldiers and Marines were killed in only six weeks from October to November of 1918 in the Battle of the Meuse-Argonne in World War I,” Milley said. “Consider also that 26,000 U.S. troops were killed in the eight weeks in the summer of 1944 from the beaches of Normandy to the liberation of Paris.”

Recalling the 58,000 Americans killed in just the summer of 1944 as World War II raged, he added, “That is the human cost of great-power war. The butcher’s bill.”

Thinking back to his own graduation, Milley paraphrased a popular Bob Dylan song from the time: “we can feel the light breeze in the air. And right now as we sit here on the plain at West Point, we can see the storm flags fluttering in the wind. We can hear in the distance the loud clap of thunder. The hard rain is about to fall.”