Barbarians are a constant threat in Romans: Age of Caesar. You will find many of these huts in your suburb that need to be dealt with.

To attack a Barbarian hut you first need to move your Legion within range. Once in range, select your Legion, select the attack option and then select the hut you wish to attack. 

Once inside the battle screen, you must place your units strategically to overcome the Barbarian defences. To do this, at the bottom left of your screen, select the units you want to use and place them behind the white deployment line.  Make good use of your tactical powers such as: Deploy, to navigate your units, and Arrow Volley, to take care of Barbarians at a safe distance!

If you are finding that the Barbarian defences are too strong, try researching more combat abilities and units.  With enough research, you will find that you will soon be able to overcome the obstacles that stopped you before.

You can also upgrade your Barracks to increase the number of units you can send into battle and overwhelm the enemy with numbers.