The submarine contribution is broader than screening the amphibious force at Hong Kong. The T class was designed with Far Eastern service in mind, and Britain could add river-class and minelaying boats as the theater expands. Once Manila and a recovered Hong Kong become forward bases, British and American submarines can watch the East China Sea, report a fleet sortie, and attack Japanese merchant traffic. Their work both weakens the force that eventually comes out and gives the Allied carrier and surface fleets more warning before the main battle.
Notable Point · 2:39:14-2:39:37
Forward submarines turn the East China Sea against Japan
T-class and other Allied submarines gain forward bases from which to warn of a Japanese sortie and attack the shipping that sustains the home islands.