KYIV, Ukraine (AP) — Ukrainian President Volodymyr Zelenskyy marked the 500th day of the war Saturday by hailing the country’s soldiers in a video from a Black Sea island that became the symbol of Ukraine’s resilience in the face of the Russian invasion.

Speaking from Snake Island, Zelenskyy honoured the Ukrainian soldiers who fought for the island and all other defenders of the country, saying that reclaiming control of the island “is a great proof that Ukraine will regain every bit of its territory.”

“I want to thank — from here, from this place of victory — each of our soldiers for these 500 days,” Zelenskyy said. “Thank you to everyone who fights for Ukraine!”

It was unclear when the video was filmed. Zelenskyy was returning from Turkey on Saturday.

He announced that five commanders of the defense of the Azovstal steel plant, a gruelling months-long siege early in the war, were returning on the plane with him.

The sprawling steelworks was the last bastion of resistance as Russian forces took control of the port city of Mariupol. Its defenders became renowned among Ukrainians for holding out in wretched conditions in the plant’s tunnels and corridors.

Azovstal’s more than 2,000 defenders left the steelworks in mid-May 2022 and were taken into Russian captivity. The five leaders, some of whom were part of the Azov national guard regiment that Russia denounces as neo-Nazi, were freed in a September prisoner swap and taken to Turkey.

Under the exchange, the leaders were to remain in Turkey until the end of the war under the Turkish president’s protection. There was no immediate official explanation from Ankara or Kyiv about why they were allowed to return to Ukraine.

“The return of the leaders of the Azovites from Turkey to Ukraine is nothing more than a direct violation of the terms of the existing agreements. Moreover, in this case, the terms were violated by both the Ukrainian side and the Turkish side,” said Kremlin spokesman Dmitry Peskov.

Russian forces took control of Snake Island on February 24, 2022, the day Moscow launched its invasion, in the apparent hope of using it as a staging ground for an assault on Odesa, Ukraine’s biggest port and the headquarters of its navy.

The island took on legendary significance for Ukraine’s resistance, when Ukrainian troops there reportedly received a demand from a Russian warship to surrender or be bombed. The answer supposedly came back, “Go (expletive) yourself.”

The island’s Ukrainian defenders were captured but later freed as part of a prisoner exchange. After the island was taken, the Ukrainian military heavily bombarded the small Russian garrison there, forcing the Russians to pull back on June 30, 2022. The Russian retreat reduced the threat of a seaborne Russian attack on Odesa and helped pave the way for a deal to resume Ukrainian grain exports.

“Let the freedom that all our heroes of different times wanted for Ukraine and that must be won right now be a tribute to all those who gave their lives for Ukraine,” Zelenskyy said. “We will definitely win!”

Intense battles continued to rage Saturday in the country’s east and south as Ukrainian forces pressed their attacks against multi-layered Russian defenses in the initial stages of their counteroffensive.