The 30 Years' War began as a struggle between German Protestant princes & this Catholic "Empire"
At enormous .... had led to 
the formation of a Protestant league of German princes in 1608 and a Catholic [DOC] [TLE] the protestant revolution and the thirty years' war - Grace Life Bible ... [PAR] As time went on, both Lutheran and Catholic princes sought to strengthen ... 
cannot divorce the religious ideological struggle between Protestants and 
Catholics ... Asch, Ronald G. The Thirty Years War: The Holy Roman Empire and 
Europe 1618-48.