The Brethren were forced to operate underground and eventually dispersed across Northern Europe as far as the Low Countries, where their Bishop John Amos Comenius attempted to direct a resurgence. The largest remaining communities of the Brethren were located in Leszno () in Poland, which had historically strong ties with the Czechs, and small, isolated groups in Moravia. These latter are referred to as "the Hidden Seed" which John Amos Comenius had prayed would preserve the evangelical faith in the land of the fathers.