The Battle Arena is a place where Captains are be constantly vying for top honors. Just as you must put in considerable time and effort to climb the ranks, maintaining those ranks will also require virtually daily investment.
Player who have not yet participated in the Battle Arena will find themselves unranked in all three Divisions (Commander, Captain, and Admiral). As you begin to participate in any one of these Divisions, your victories will earn you a place on the leaderboard.
However, should you not continue to compete in that Division, after 14 days of inactivity you will become eligible to have your rank removed in order to make room for those who are actively participating. Even as you reach a commendable rank in one Division and turn your attention to another, you will still want to compete daily in any Division in which you hold a rank, lest your accomplishments be forfeit.