just don't give anny exp to anny ship that retreats
as for the subs not retreating aslong as they have torps they can sink u and are in titel to play there game i dont see bb5/6 retreating if there the last one standing with ammo left
but its a 2 way street if the sub is retreating don't shoot it u will make it mad and it may dicide to play out the game
i have been the last sub alive several times and have been able to win the battle for my team but have also been the sub that retreats for the enemy so they can win there game