Tens of thousands of Russians marched in processions through major cities on Monday for an event called the Immortal Regiment -- meant to commemorate relatives who fought and died in World War II. But the marches were also co-opted by the Kremlin to support the Ukrainian invasion.

Many Russians believe the Kremlin's false narrative that Russia is justified in fighting in Ukraine. Some said Russian forces are now repeating the same feats as their ancestors and vehemently backed Russian President Vladimir Putin.

Two women told ABC News that "Kyiv is Russia" originally, adding, “We are winning and we will win."

Russian forces remain stalled in multiple parts of Ukraine, according to a senior U.S. defense official.

The Russians are only making incremental progress in the northern Donbas region "because the Ukrainians keep pushing them back and keep fighting them back," the official said.

The official described Russian movements in southern Ukraine as "stalled" with "virtually no progress."

In Kharkiv, the Ukrainians are continuing to push Russian forces east of the city.

"The Ukrainians are actually pushing them east into the northern Donbas," the official said. "They're not been able to go through or around Kharkiv right now."

U.S.-supplied howitzers are already coming into play for the Ukrainians. Eighty-five of the 90 American-made howitzers are now inside of Ukraine, along with significant amounts of ammunition sent by the U.S., the official said.

"These howitzers are already in the fight," the official said.

-ABC News' Luis Martinez

Ukrainian President Vladimir Zelenskyy released a video message from Kyiv early Monday to mark the World War II victory over Nazi Germany, telling his country that "very soon there will be two Victory Days in Ukraine."

"Today, we celebrate the Day of Victory over Nazism. And we will not give anyone a single piece of our history," Zelenskyy said. "We are proud of our ancestors who, together with other nations in the anti-Hitler coalition, defeated Nazism. And we will not allow anyone to annex this victory, we will not allow it to be appropriated."

"On the Day of Victory over Nazism, we are fighting for a new victory," he added. "The road to it is difficult, but we have no doubt that we will win."

Zelenskyy's remarks came just hours before Russian President Vladimir Putin delivered a patriotic speech in Moscow's Red Square on Monday morning during a military parade for Victory Day, a national holiday in Russia commemorating the Soviet Union's defeat of the Nazis in 1945. Putin defended his invasion of neighboring Ukraine, telling Russian troops: "You are fighting for the motherland, for its future, so that no one forgets the lessons of the Second World War."

During a military parade in Moscow on Monday, Russian President Vladimir Putin addressed his troops fighting in neighboring Ukraine but offered little insight into his next steps.

"You are fighting for the motherland, for its future, so that no one forgets the lessons of the Second World War," Putin said in a patriotic speech for Victory Day, a national holiday in Russia commemorating the Soviet Union's defeat of Nazi Germany in World War II.

Columns of Russian soldiers marched through Moscow's Red Square, alongside tanks and other military vehicles boasting huge intercontinental ballistic missiles.

"Now here, on the Red Square, soldiers and officers from many regions of our vast homeland stand shoulder to shoulder, including those who came directly from Donbas, directly from the combat zone," Putin said.

Although he showed no signs of backing down, the Russian leader did not make any declarations of war, peace or victory during his remarks on Monday. He drew parallels between Soviet soldiers battling Nazi troops and the Russian forces fighting now in Ukraine, as he has vowed to "de-Nazify" the former Soviet republic. He also spoke of the disputed Donbas region of eastern Ukraine as if it was already part of Russia.

"These days, you are fighting for our people in the Donbas. For the security of our homeland, Russia," he said. "You are defending what fathers and grandfathers, great-grandfathers fought for."

Putin accused Ukraine of seeking to attain nuclear weapons and planning a "punitive operation in the Donbas, for an invasion of our historical lands, including Crimea." He also laid blame on the West for refusing to have "an honest dialogue" about Russia's demands for formal guarantees that Ukraine will never join NATO and that the alliance will pull back its forces from countries in eastern Europe that joined after the Cold War.

"Thus, an absolutely unacceptable threat was systematically created for us and directly at our borders," Putin added. "The danger was growing everyday."

He claimed that attacking Ukraine "was a forced, timely and only right decision -- the decision of a sovereign, strong, independent country."

"Russia has given a preemptive rebuff to aggression," he said.

Jalina Porter, the State Department's deputy spokesperson, is responding to the Russian attack at a Ukraine train station that killed at least 50, saying, "We can no longer be surprised by the Kremlin's repugnant disregard for human life."

Five children were among those killed when Russian rockets struck the station in Kramatorsk in Donetsk Oblast on Friday morning, according to Ukraine's state-owned railway company. At least 100 people were injured, according to Donetsk Oblast Gov. Pavlo Kyrylenko.

Russia has denied involvement in the attack, which occurred as "thousands" of civilians fleeing the Russian invasion were at the train station waiting to be taken to "safer regions of Ukraine," according to Kyrylenko.

"Civilians are killed when they stay in their homes, and they're killed when they try to leave," Porter said. "Actions like these demonstrate why Russia did not belong on the U.N. Human Rights Council, and they also reinforce the U.S. assessment that members of Russian forces are committing war crimes in Ukraine."

Porter declined to say if the department considers the train station attack a war crime, saying, "Assessing individual criminal liability in specific cases is the responsibility of courts, as well as other investigatory bodies. But as the secretary, Secretary [of State Antony] Blinken, has said, 'Those responsible for war crimes and other atrocities committed in Ukraine will be held to account.'"

-ABC News' Conor Finnegan