How many modern ships would Britain need before sending older carriers and battlecruisers east as a real deterrent to Japan?
Short answerA token force is not enough; Britain needs a flexible multi-carrier Eastern Fleet based safely in the Indian Ocean and able to reinforce either theater.
NotesThe initial estimate for freeing two older carriers and two battlecruisers calls for three Illustrious-class carriers and four King George V-class battleships already in service. The discussion then questions whether such a 1939 deployment would help, since sending a small force can reveal the maximum Britain is able to spare. Sustaining a more imposing force later could require four or five carriers and comparable capital-ship strength, tying up ships needed elsewhere. An Eastern Fleet based around Ceylon is preferred because it could train, rotate ships with the Mediterranean, and move east when required. A Japanese strike into the Indian Ocean before the fall of Singapore and the Dutch East Indies would have to pass through Southeast Asian straits, making a large carrier force harder to conceal. Major refits would take place safely in India. The time matters: Japan's fleet in 1939 had yet to reach its late-1941 strength, and a British force alongside the American fleet could force Japan to consider two separate opponents.