[Bug] Tactical Battle AI not moving

Alright on a second tier city I had been just building up to see the techs and different paths for the heroes; when I got attacked by a 6 unit army of 3 man units.  I decided to retreat to the back corner to set my archer into the farthest corner and then put my 3 militia units surrounding my archer unit.  Once I had this set up the AI stopped moving.  So once the archer was unable to be attacked the AI stopped moving towards my units.  I hope this makes sense.