Leveling up in Battlecry is based on the amount of experience (XP) you earn.
You gain XP primarily by completing Operations and winning battles against other players. As you collect enough XP, you level up and unlock new features, zones, and stronger units.
Your level also affects several gameplay limits. For example, the number of commanders you can use in battle is equal to your level. It also determines how many captains you can have and how much you can store in your treasury.
Higher levels mean more power, more options, and access to advanced gameplay features.