[dmm]

Yeah, Marco has a good point. Although:
a) the AI is never going to do that, and
b) you would need 8 ships per warp point if the WPs aren't at the system edge (and otherwise, you'd still need 5 per WP)

Question1: In SEIII retreat, can you go diagonally? If not, that reduces problem b) by a factor of 2.
Question2: Do mines/satellites/fighters count as unfriendly units to prevent retreat? If they do, then warp point defense isn't much harder at all.