As Ukraine begins its fifth year of war with Russia, President Zelenskyy offered the world a remarkable and deeply personal look behind the scenes, inside the underground bunker in the heart of Kiev where he and his closest aides spent the first harrowing days after Russia's full scale invasion.

Zelenskyy revealed the inner workings of the bunker, walking through the long concrete corridors and cramped rooms where staff worked around the clock coordinating Ukraine's defense and calling for support. Above ground, Russian missiles struck targets across the capital. Intelligence warnings spoke of airborne assaults and assassination teams.

It was here, Zelenskyy recalled, that he took one of the defining decisions of the war, answering an evacuation offer from US leaders not with a plea for safety, but with the now famous words: "I need ammunition, not a ride."

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And on the fourth anniversary of the conflict, Zelenskyy signaled that Ukraine is prepared to fight on. Ideally this will come with the support of the United States, but no matter what, he says, there will be no surrender.