Protestants were offered an ultimatum. They were forced to choose to either leave the many and varied southeastern principalities of what was the Holy Roman Empire (mainly Austria, Hungary, Bohemia, Moravia, Silesia and parts of Germany and its many states), or to practice their beliefs secretly. The Brethren were forced to operate underground and eventually dispersed across Northern Europe as far as the Low Countries, where Bishop John Amos Comenius attempted to direct a resurgence. The largest remaining communities of the Brethren were located in Lissa in Poland, which had historically strong ties with the Czechs, and in small, isolated groups in Moravia.