In many RTS games tech advances are almost exclusively military (e.g. StarCraft). But in most TBS and some RTS games the research and production costs of top-end military techs are so high that you have to build up your economy and your research productivity first (RTS – Age of Empires and Empire Earth, where one of the most significant costs is going up an epoch; TBS – the Civilization series and Master of Orion series).