“Special Defense Features
Feature 1 ALL surface ships can engage a defending Sub. But if no DD is present with the attacking force, the SS can simply submerge before combat.”
Example: 1 BB attacks 1 sub, BB rolls a 5 and misses, the sub can then choose to stay and fight or submerge? Or if the BB attacks 1 sub and rolls a 4 or less, the sub is not hit if he chooses to submerge?
This is slightly better than AAR, this means that if the attacker does not include a DD with the attacking force, the subs can always choose not fight, and thereby survive every combat if not attacked by DD’s.
Conclusion: Attacker needs DD’s when attacking subs.