A police officer I knew got me into this game.  I didn't think much of it because it was essentially the same game design as the venerable DUNE and War Craft games.  One Age of Empires, as originally designed, was never meant to be the huge slug fest that it ultimately turned into.  The icons on the map were meant to be just that; icons representing single armies.  But the players demanded more, and a patch was released allowing multiple units to be manifested on the map.  Result, that icon that was supposed to represent an army suddenly became a single unit in the army.