English Civil War
The English Civil War (or wars, as they are often broken into three or four wars) was a very complex conflict. No over-simplified "Roundheads vs. Cavaliers" explaination will make much sense of the events in the 1640's and through late 1650's.
The poster's inclination is to put part of the blame for the ECW on the nearly-finished 30 Years War in Europe. In many ways it would have been strange for England to not become involved in this massive Catholic vs Protestant conflict that severely depopulated portions of Europe and established what many historians consider to be the era of "modern" warfare.
Here are some online resources, including reenactment organizations websites:
http://www.open2.net/civilwar/
http://history.boisestate.edu/westciv/english/
