The 30 Years' War began as a struggle between German Protestant princes & this Catholic "Empire"
[DOC] [TLE] Thirty Years' War | European history | Britannica.com [PAR] Thirty Years' War, (161848), in European history, a series of wars fought by ... to 
impose Roman Catholic absolutism on his domains, and the Protestant ... four-
year war with Poland, invaded Germany and won many German princes ...