Japan needs a southern base after excluding the Philippines from its opening attacks. In this scenario, Taiwan is too lightly developed and Japanese-held areas of China are too distant for the task. French Indochina had required about a year of construction and consolidation after the Japanese move there in September 1940, while Vietnamese resistance added further strain. The estimate uses roughly 130,000 troops for Malaya and about 110,000 for the Dutch East Indies, with part of the latter force historically moving through the Philippines. Combining these demands would put the best part of 300,000 personnel into Indochina. The concentration is possible, but the ports, depots, and transport network need more time before the invasion can begin.
Chapter · 6:53-11:13
Why the southern offensives must concentrate in Indochina
With Taiwan underdeveloped and occupied China too distant, Japan must concentrate nearly 300,000 troops in French Indochina for the attacks on Malaya and the Dutch East Indies.