Japan's problem in this counterfactual is that a surprise attack could strike either the British or American fleet, leaving the other available. Retained China Station submarine patrols are proposed as an obstacle to secretly sending the Japanese carrier force toward Singapore. A submarine that encountered the force could report its movement before an attack. The British fleet might also remain farther west at bases in the Indian Ocean, making a concealed approach still more difficult. These complications support the suggestion that Hawaii could remain the more attractive target, even with a much stronger British fleet in the wider theater.
Notable Point · 1:26:14-1:27:57
British submarine patrols and a Japanese surprise attack
In the all-submarine Germany scenario, retained British patrols and a fleet based farther west complicate Japan's ability to launch a surprise attack.