(1.0.2 [fc5e]) Declared war but we can't fight at all

[grimitar]

My large empire declared war on a tiny one to get them to cede their last planet to me, war declaration went off fine, popped in my fleet but can't bombard. My fleet won't attack their stations, and the option to land armies is red, saying we have to declare our aggression. In the corner though, the war-score badge is there.

EDIT: Just double-checked, it may be because the planet is apparently already occupied by the army of a different empire that I am not at war with.