On February 24, 2022, Stepan Bandrivskyi woke up before dawn and got ready for a special day: his birthday.It wouldn’t be a particularly happy one. Hours earlier, a couple dozen miles away, Russian tanks had rolled across the borders of his native Ukraine. The full-scale invasion had begun.Like so many other Ukrainians, Bandrivskyi didn’t know what to do. So he went to work, to the Soledar Salt Mine, a cavernous state-run operation in Eastern Ukraine. Kyiv says it is the biggest such mine in Eur...