“On February 24, everything changed,” said Ms. Chornohuz, who at 27 has fought for a decade for a democratic Ukraine with a European perspective. Before she was a warrior, she was an activist. In 2013, when the Euromaidan protests broke out, she was a literature student in the capital, Kyiv, who joined the revolution to oust Viktor Yanukovych, the pro-Russian president. A struggle over Ukraine’s future was underway, with the Kremlin backing pro-Russian forces inside the country opposed to greater integration with the West. Young activists like Ms. Chornohuz threw themselves into promoting the Ukrainian language as a cornerstone of a national identity free from Moscow’s influence. “I was one of those Ukrainians who understood long before 2014 that Russia would attack us one day,” he said, describing growing up in a Ukrainian-speaking family and reading works by Ukrainian dissidents killed during the Great Terror of the 1930s. Worried about losing a sphere of influence and a buffer zone, Russia soon annexed Crimea and began supporting separatists in the Donbass region. In April 2014, as Ukrainians began forming volunteer self-defense groups to fend off armed separatists, Ms. Chornohuz wanted to join, but became a mother instead. “I gave birth to her the same day the war officially started,” she said, explaining how raising her daughter initially prevented her from taking a more active role in the war. “I knew that our country and our nation had been suffocated for centuries in the Russian empire and the Soviet Union,” he said. “I felt that I had to participate in this struggle for the survival of my nation, as my people did a century ago.”