I just love this feature in my current game. I have a hud planet with 3 of my planets adjacent and 4 of the AI.
Before I neutered most they ran into the number they spawned barracks, still over 1k ships on each planet outside the barracks.
None of them attacked, even an 1200ship strong CPA seemed to wait at the enemy gate.
Little later a wave hits me .... all planets release their ships and I have over 2k ships to battle on my planet and more dripping in
Am I glad I just unlocked fortresses and actually placed 2 on that planet as I needed to shed some Rs
They attack, but somehow tend to pick the most painfull moments to do so ... Chris and/or Keith should have become teacher ....