Based on the epic poem of the same name from the Royal Court Manuscript which describes the Czech uprising against the Franks at the beginning of the ninth century 805.
Charlemagne`s troops led by Ludek invaded Bohemia. The Franks wanted to impose the Christian religion on the pagan Czechs. The Czech leaders Zaboy and Slavoy rebelled defeated the Franks and expelled them.

https//cs.wikisource.org/wiki/Rukopis_královédvorský/Záboj_Slavoj_i_Luděk