Each unit is allowed to have up to 2 officers, these may roam within reasonable distance to their respective units, reasonable being within the admin´s leisure.
OA is allowed when
the officer charges,
the officer was hit by a cannonball,
the officer actively trying to block bullets for his men
the officer stands inside a square,
but not allowed when
the officer takes cover,
the officer is leading a line,
the officers stands next to his line, or
the officer stands on a hill by himself