Taking place in the year 2104, Mars has more than 700 million people living on it and Earth carries all their space projects on Mars. As months goes by, Mars becomes more powerful and they decide to gain independence from Earth. Things get out of hand and war is declared between the 2 factions. But that's just the beginning of their problems, as alien forces start to appear out of nowhere. In desperation, Mars and Earth form the Legions of Iron to fight back.

Haegemonia is a space based 3D RTS, very similar to games like the Imperium Galactica series but without the ground battles. The player will have to colonize nearby planets, research new technologies, build up his/her fleet to battle enemy forces, use spying tech and also manage colonies. Haegemonia emphasizes more on space battle than micromanagement.