The rules specify that:
Ground Forces destroyed by bombardment are removed immediately, do not receive return fire, and will not participate in the upcoming Invasion Combat.
However, some political cards, action cards and special abilities refer to "When invading a planet with a Ground Force on it". So, if one invades a planet with Ground Forces on it, bombards them to death and then have a successful invasion, does that count for "when invading a planet with Ground Forces on it"?
(Sure, the Ground Forces did not count for the invasion combat, but they might count for the invasion itself as a whole..?)