Historically, Wilhelm Heidkamp maneuvered to about 700 meters and aligned her tubes before the fight began. A mutually supporting coastal-defence ship could observe and challenge that positioning. The second ship could question the destroyer's movements while Eidsvold handled the German emissary, denying the attacker an uncontested firing setup. Restoring mutual support is the main tactical change in this part of the counterfactual.
Notable Point · 15:35-16:47
Mutual support changes the torpedo problem
A second heavy ship beside Eidsvold would make it harder for a German destroyer to prepare a point-blank torpedo attack unnoticed.