Japanese capital-ship availability rules out sending the entire battle fleet. Two or perhaps three Kongo-class ships could deploy first, with one supporting Force H and the others strengthening the Home Fleet against German breakouts. Nagato and Mutsu would take longer to prepare, but their 16-inch guns make them valuable in northern waters, while older or unfinished battleships remain in Japan. The opening estimate allows them to head out in late October or early November after a June decision. Cruisers and destroyers would accompany the formation, and the detachment would reinforce Cunningham's Mediterranean command. A Japanese admiral and ships would need working Allied communications and command arrangements. British and Japanese forces had pointed guns at one another in 1939, and the January 1940 Asama Maru incident had sharpened tensions only months before the proposed alliance.
Chapter · 9:50-16:47
Kongos and Nagatos reinforce different Allied fleets
Speed, readiness, and gun power send one Kongo toward Force H, other fast ships toward the Home Fleet, and the Nagato class toward Atlantic blocking duties.