Languages rise and fall with history, in nations and university language departments alike. In 1980, when Roman Koropeckyj stepped into his classroom at Harvard to teach Polish, he was “gobsmacked” by the dozens of students awaiting him. The Polish trade unionists of the Solidarity movement, who were defying Soviet oppression on the opposite side of the planet, had inspired Americans to learn. Another one of those linguistic flashpoints arrived in February, when Ukraine’s staunch resistance to a massive Russian invasion drew admirers around the world. The Ukrainian language hasn’t been taught …