Ranks in Halo Wars are earned by accumulating score from Public Matchmaking games on Xbox LIVE.
Your Service Record shows your current Rank, Score and how many more points you need to rank up. Your Rank is also visible as an icon next to your gamertag when in a game lobby, post game screen and other areas.
There are eight ranks available in Halo Wars. You start as Unranked and then are promoted to Recruit upon completing your first Public Matchmade game.