Agios Nikolaos - Anavyssos
However, since losses are rounded down the only time you can inflict losses on an enemy with less than 4 warbands is if you have allies/citadel/leader that helps you take control.
E.g. a region with the 3 Arverni allies, 3 Arverni warbands, Vercingetorix, and 6 enemy warbands of one faction will inflict 2 looses on the enemy, but not take any losses themselves.
I knew that you could devastate without loosing Wb, but I thought that in order for removing 1 out of 3 enemy you should remove your too. Thanks for letting me know