"now that that whole war business".. except no war, we've been allies since it was possible.
Even better, I'll send them transports loaded with troops I bought from their enemy, park them right outside the enemy planets, with defensive ships....
... they don't invade... they fly away.
Let me recap. I've laid waste to the enemy defenses, moved transports into position, complete with defending fleets that their enemy cannot possibly destroy, and given them the keys... and they do nothing.
I don't *want* these planets, I want to bolster my ally, but it is effectively impossible because they simply won't defend themselves.
This is, of course, additionally compounded by the fact I had to wait x number of turns, refraining from trading with my ally for an extended period, simply to ensure I could deliver these battle ships on time, as for some strange reason, its particularly difficult to help you ally when they are getting their asses handed to them in a war.
There should really be a secondary diplomatic option to provide war aid, completely separate from typical trading, which bypasses the lockout, and doesn't provide you with the option for gain.
Here, take my Mace +1.