The Spanish Civil War, of course.

I haven't done much studying of the Spanish-American War, but I have done a little. I can recommend a book that describes the war against the Spanish and later the guerrillas in the Philippines.
"A War of Frontier and Empire" The Philippine-American War 1899-1902. by David J Silbey. There's alot about the US navy action in Manila harbor that is really interesting. Its a good read, and not too long.
