A declaration on 25 June would still leave fleets to be assembled, supplied, and sent west. Mediterranean arrivals are estimated for late July or early August, with Atlantic forces following in August or September. Joint command, combat cooperation, and information sharing would then take months to establish. Changes to Japanese aircraft development would therefore be more plausible in 1941, after operational experience and British information had reached the relevant organisations.
Notable Point · 1:59:09-2:00:21
Fleet movement and joint command take months
Weeks of movement and months of joint preparation would separate Japan's declaration from its effective participation in Allied operations.