Watching footage of Russian attacks on Ukraine, Jonathan Tseng thought: That could happen here, too.

So from his home in Taiwan, Jonathan — Tseng Sheng-Guang in Chinese — resolved to take up arms against Russia. He left his wife, son and his beseeching mother in June 2022 to join the ranks of foreign fighters in Ukraine. His decision mirrored his own fears about unwelcome aggression on Taiwan, should China move beyond decades of warnings and threats, and into open conflict, against the island it claims as its own.

Bloomberg reporter Yang Yang spent several months looking for and talking to Jonathan’s family, friends and fellow soldiers in Ukraine, in order to understand more about what drove a young Taiwanese man to battle a neighboring aggressor, and what happened to him there.