Hiding for days in the basement of a kindergarten in Bucha, the Kyiv suburb that became synonymous with Russian war crimes, Oksana Semenik had time to think.

Outside, Russian troops were rampaging through the town, killing civilians who ventured into the streets. Knowing she might not make it out, Ms. Semenik, an art historian, mulled over the Ukrainian artworks she had long wanted to write about — and which were now in danger of disappearing.

That time spent holed up in Bucha was during the early days of Russia’s full-scale invasion, but even then, two years ago, she had already seen reports of destroyed museums. Precious folk paintings by her favorite artist, Maria Primachenko, had gone up in flames. Moscow, she realized, was waging a war on Ukrainian culture.

“They’re destroying artworks. They’re destroying museums. They’re destroying architecture,” Ms. Semenik recalled thinking in the basement. She vowed that if she escaped from Bucha, she would not allow Ukrainian art to fall into oblivion. “It was like: ‘There’s a war. You can die any minute. You should not postpone all this research any longer.’”

Ever since, Ms. Semenik, 26, has been working to fulfill that vow.

After fleeing Bucha on foot, she started “Ukrainian Art History,” an English-language account on the social platform X, where for the past 21 months she has been posting daily about the lives and works of long-overlooked Ukrainian artists. Her posts, which have often exceeded 100,000 views, have become a go-to resource for learning about Ukrainian art.