This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
In 1620, Bohemia's Protestant nobility suffered defeat at the Battle of White Mountain, and the Habsburg victory that followed drove the Unity of the Brethren underground across the kingdom it had organized in more than a century and a half earlier. The nobles who had protected the Brethren's open practice were expelled from Bohemia in the defeat's aftermath, taking with them the political protection the movement had relied on since its founding at Kunvald in 1457.
The Brethren who could leave did: the largest surviving communities regrouped in exile at Leszno, in Poland, rebuilding an organized life outside the reach of the Habsburg crown that had broken their standing at home. Those who stayed behind in Moravia could not organize openly at all; scattered in small isolated groups, they became known to later generations as the Hidden Seed, a name for a Brethren presence that persisted without any visible institutional life for the century that followed.
What White Mountain changed for the Brethren's spread was continuity under a form nobody would have chosen: a movement forced apart into an organized exile community abroad and a hidden, unorganized remnant at home, both of which had to survive a century of suppression before the Hidden Seed's descendants met refugees from Moravia at Herrnhut in the 1720s and the Brethren's public life began again.