Question about colonizing.

[unmerged(659343)]

so i get the message which says that i can colonize a region however when i try to do it it says that the barbarians in this region are too strong so i can`t colonize the region.
now the question is: how am i supposed to decrease their power? i sent an army to that region but nothing happened so i guess i have to do something else?

 

[Antiochus_Soter]

Just send in 1 cohort of velites and leave your big army in your own adjacent province. Then you just ahve to sit and wait for the barbarians to rise up, when they do they will defeat your little 1 cohort army and then you send the big army in to crush them.