Like all Library research, Military research has a total of 7 levels to research. Each level researched... * increases the Population Limit by +25, up to a maximum of 200. * unlocks all military units of the same age. * reduces production cost for units of previous ages by 5% per level ahead * reduces upgrade cost for units of previous ages by 10% per level ahead Researching Military technology also unlocks all military structures (except Docks) as well as Fort technologies: