Sid Meier's Civilization 4 Complete

Ive got Sid Meier's Civilization 4 Complete and am really not sure which version to play?
I realise that Civ4 is the first, Warlords second and Beyond The Sword is third but am I correct in thinking that BTS is the one to use? Im asking because in the manual for BTS it states 'try Warlords', so if im loading BTS does it contain all the content from the previous titles? Just thought by buying the 'Complete' version it would have a version that did contain all the content, the tech tree sheet I got has all three episode tech trees on, so am I missing something?

Thanks

Darkspire