Past:

Footmen: Guys in magic armor at least as good as kevlar. haha.

Enchanted catapults: Catapults fired with blue flaming bolts, capable of some serious damage.

Dragons: The infamous flying dragons with all over armor, razor sharp giant claws and flaming breath. Tough? I think so.

Galleons: Allows you to send aid to other empires and provide great military strength, even compared to Dragons

Wizards: Men and women trained in the arcane arts. Their spells are diverse and little is known of what these mysteriuos people can actually accomplish.

Present:

Infantry: Basic ground unit, equipped with minimal training, light armor, and a rifle.

Tanks: If you don't know what a tank is, then go back under that rock you live under.

Helis: Only the toughest attack helicopters known to mankind.

Battleships: Allows you to send aid to other empires and provide great military strength, even compared to Helis

Telepaths: Gathered from all over your lands, they have been trained and honed to be a force capable of dealing with the wizards and AI's.

Future:

Cyborgs: Humans adapted with special armor and weapons, designed to be a first wave assault. Luckily they're so drugged up, they're pretty stupid.

Mechanized Warriors: Non-drugged or adapted humans that are just traitors put into a tough exo-skeleton of metal and hardware. Very tough.

Dreadnaughts: Small flying fighters, armored and highly weaponed.

Hovercraft: Allows you to send aid to other empires and provide great military strength, even compared to Dreadnaughts

Master AI's: The intelligent force that drives your nations. Also the only things capable of combating wizards and telepaths and do some damage to other countries at the same time.