This is a rather simple trophy. Simply become a ruler and invade another kingdom, selecting yourself as the only officer. Once in battle kill at least one enemy officer and finish the stage. The trophy should pop some time after the battle.
Please note:
-Having an allied kingdom will make this trophy impossible/more difficult as they can supply you with reinforcements in the battle.
-Creating a custom scenario will make this trophy easier as you can make your kingdom strong quickly and with ease.