I'm playing the 2004 Avalon Hill Revised rules.
Scenario: It is the UK player's turn. They use their Atlantic fleet (without any destroyers) to attack the German Atlantic fleet. Most of the German fleet is destroyed except for two submarines which choose to submerge. At the end of the UK player's non-combat move, the German submarines resurface and remain in the same sea zone as the UK fleet.
Fast-forward to the USA player's turn. They want to use their Atlantic fleet to attack the remaining German submarines. These submarines are still parked in the same sea zone as the UK fleet.
Question: If the USA player attacks the German submarines in the same sea zone as the UK fleet, does the UK fleet participate in the attack?
Commentary: I'm leaning towards no because of the "Defend together. Attack separately." principle. However, I can't find where this scenario is clarified in the rules.