[medved]

Sorry, you're right, forgot about the Swedes. I see that one as essentially similar to the wars of Chengis Khan, i.e. motivated by a drive for power coupled with military innovation and a desire to test out new theories of warfare and political organization; best treatise on the topic I've seen is the WestPoint Military History series dealing with that time period. Those factors allowed one of the usual European wars to spin out of control. Correct me if I'm wrong, but I don't really see Gustavus Adolphus motivated by some lunatic rage to kill catholics.

[Doctor Stochastic]

You're right about Gustavus Adophus. The 30-years war started as a religious war but later changed into a more politically oriented conflict as varous groups changed sides. The contemporary estimates of 26 million dead seem too high. There may have been 26 million displaced, which is probably where the estimates came from. Many villages were erased during the war, but the populace may have just moved.

A more religiously oriented war would be the struggles under Elizabeth I. Before there were Catholics and Protestants in England. Later there were English who happened to be Catholic and English who happened to be Protestant. The Cromwell reign was also religious in nature includeing the destruction of much of the religious music of England.