With a Ukrainian military honor guard standing ramrod straight beside his coffin, Andriy Melnyk, a leader of a Ukrainian nationalist movement who died six decades ago — and who has been no less divisive after death than in life — lay in state in Kyiv before his reburial on Sunday.

President Volodymyr Zelensky provided full state honors for the ritual, signaling a deep shift in Ukrainian politics after Russia’s invasion in 2022. Before then, Mr. Zelensky had kept nationalist politics at arm’s length; in the reburial, he embraced them.

The remains of the long-dead World War II-era Ukrainian leader were exhumed in Luxembourg, where he had been buried after dying in exile in 1964, and returned to Ukraine. There was none of the raw grief of today’s war funerals.

Melnyk led one of two factions of the Organization of Ukrainian Nationalists, including through a period of alignment with the Nazi army during its occupation of Ukraine, which was one of the bloodiest chapters of World War II.

The Soviet Union signed a nonaggression pact with Germany in 1939 and was caught by surprise two years later when the Nazis invaded Ukraine, then Soviet territory. Ukrainians had suffered greatly under Soviet rule, and many initially saw the Nazis as liberators.

Factions from the Organization of Ukrainian Nationalists and its insurgent army fought alongside the Nazis in what they viewed as a struggle for Ukrainian sovereignty. Members of those groups also took part in atrocities against Jewish and Polish civilians. Later in the war, some of the groups fought against the Nazis.

As he was under arrest in Germany through most of the war, Melnyk’s degree of culpability in the Holocaust and a murderous fight with ethnic Poles in western Ukraine in 1945 has divided historians ever since.

His body lay in state in the towering Greek Catholic cathedral of the Resurrection of Christ in Kyiv before being transferred to a final resting place in a new military cemetery outside the city.

Before Russia’s all-out invasion the ceremony would have been a risky move by any Ukrainian politician who wanted to win votes from Russian speakers. But during the war, Ukrainians have embraced more tightly all symbols of Ukrainian independence, and Mr. Zelensky moved with them.

The president had campaigned in 2019 on a promise of negotiating a peace agreement with Russia, and had studiously avoided the memory politics of World War II. He declined to state his personal views of midcentury Ukrainian independence leaders like Melnyk.

In 2020, for example, speaking with a Ukrainian news outlet about Stepan Bandera, who led the rival group to Melnyk’s, he said that in Ukraine’s fraught wartime history “the line between hero and enemy can be very thin.” Mr. Zelensky had opposed naming streets after Bandera.

After the invasion, Mr. Zelensky warmed to the World War II history of partisan resistance against the Soviets. That year, he awarded a 99-year-old veteran of the Ukrainian Partisan Army the country’s highest military honor, Hero of Ukraine.

This month, Mr. Zelensky went a step further by repatriating Melnyk’s remains for burial in the new military cemetery, elevating him to the country’s pantheon of heroes.

“Something that Ukrainians and Ukraine have long hoped” for was underway, he said as the cremated remains were en route back to Ukraine. He described Melnyk and his wife, Sofia Fedak-Melnyk, who was reburied beside her husband, as “iconic Ukrainians of the 20th century who are deeply respected.”

What accounts for Mr. Zelensky’s change of heart?

Like the rest of the country, said Yurii Makarov, the former editor in chief of Ukraine’s public broadcasting company, the president “turned on national identity mode” during the war, amid a growing hatred of Russia. “Ukrainians became patriots because cruel life taught them there are no alternatives,” he said.

Mr. Zelensky, unsurprisingly, has also moved away from a preinvasion policy of supporting a state-run Russian-language broadcasting service.

To be sure, right-wing parties have had historically low support in Ukraine, and none cleared the threshold to enter Parliament in the last election before the invasion, in 2019. But Mr. Zelensky’s embrace of Melnyk, a figure previously revered most fervently by the right, is telling of a wartime shift, an unintended consequence of the war for Russia.

The move is also a significant step for Mr. Zelensky, Ukraine’s first Jewish president, in formalizing the national commemoration of a figure criticized as a Nazi collaborator while also honored in Ukraine as an independence fighter.

A crowd of about 300 people turned out for the service, administered by priests in crimson frocks as the coffins lay under the soaring cupola of the cathedral, draped in a Ukrainian flag.

“He is quite a contradictory person but still very important” for Ukraine, said Oksana Khomyak, a lecturer at a Kyiv University who attended the ceremony. She noted that her grandfather had fought in the Ukrainian Partisan Army in World War II.

“I don’t approve that they fought with German help,” she said of the pro-independence forces, who are seen in Ukraine as the forebears of the soldiers fighting Russia today. “It cast a big shadow over the Ukrainian national movement. But if you ask me who is right and who is wrong, I cannot tell you.”

Anna Lukinova and Nataliia Novosolova contributed reporting from Kyiv.