The ensign carries the flag into the midst of the battle, accompanying his team mates and encouraging them with the sights of their homeland, inspiring them to fight for glory!
The flag carrier in Field of arms serves an important purpose in the game, if an ensign from the attacking team reaches the capture point location; it will boost the capture speed of such area, greatly increasing the chances of succeeding and winning the battle. If an ensign of the defending team is in the capture point location it will count for two players making the time to decrease the capture go down faster.
By choosing the ensign you are getting yourself into a high risk but high reward position as you will surely be a primary target for the enemy team to take down, the sight of the enemy flag represents an imminent threat for the opposing team, as letting an ensign into the capture area will increase the difficulty of obtaining victory.
So if you are brave enough to be the ensign and carry your flag to victory, be welcomed to do so, just beware of the target on your back!