I have a problem. I'm playing two sides and I'm trying to perform a planetary invasion against a body defended by STOs. The STOs are not firing. As far as I can determine this is because they see the incoming vessels as neutral and I can't change the race in the relations screen to hostile. If I artificially increase DR score I can choose from many options such as friendly or whatever but now matter what I do I cannot set the other race to hostile. Is this a bug or am I doing something wrong?
Set race A's diplo rating with B to -999, set race B's diplo rating with A to -999,
advance time 5 days (or whatever is necessary to trigger a production cycle), tick the box on A's window to set race B as hostile, and the box on B's window to set race A as hostile.
And double-check the origin of the ground forces -- if they were originally commercial (i.e. CMC garrison) they might not be "yours" in the empire sense.