Submarine Warfare will be handled in the same way that Espionage operations are conducted. A player will send out his Submarine on patrol then PM an Admin, (Nick, Skrevski or myself) with their attack plan. Submarine Operations will not cost any money, all you need is a Submarine and a plan of attack.
For example, a German U-Boat is attacking a British Convoy. The attacking player will PM an admin with his plan of attack (Written in much the same way as a normal post for combat) The U-Boat fires a pair of Torpedos into a Destroyer and fires two more into a transport ship before falling back. The Admin will then inform the attacking player and Defending player what losses (if any) they have taken.