740.0011 Pacific War/2959
Memorandum by the Chief of the Division of Far Eastern Affairs (Hamilton) to the Adviser an Political Relations (Hornbeck)64
Mr. Hornbeck: Reference is made to the underlying memoranda65 in regard to a possible offensive against China from Burma and/or Indochina.
Without considering the factual likelihood of an immediate attack on Yunnan Province, it may be pointed out that the Japanese probably have one strong incentive for making such an attack, in addition to the objectives usually mentioned of (1) closing the back door of China to foreign aid, and (2) making a drive on Chungking feasible. This third objective would be the opening of a land route from Haiphong to Rangoon, using existing rail and highway facilities. While the Haiphong–Kunming railway has been partly destroyed by the Chinese for a distance of possibly 200 kilometers northward from the Indochina–Yunnan border (rails have been taken up in this stretch, bridges and tunnels largely demolished), the Japanese could probably put the entire Yunnan section of the line into operation within a reasonable length of time by the use of impressed coolie labor. The roadbed has not been effectually destroyed. From Kunming the Burma Road leads directly to the Japanese-held railhead at Lashio, Burma. Control of this route would reduce considerably the strain on Japanese shipping while affording ready means for supporting defense of Burma against Allied attempts to reestablish a land route to China through Burma or an offensive against India.
The possibility of Japanese success in occupying this new route is probably greater than would be the chances of complete seizure of the Peiping-Hankow-Canton rail line as part of a land route from Korea to Bangkok (or Singapore). The eastern Yunnan terrain is considered by many commentators as impossible for military advance, given characteristic Chinese resistance. However, the Japanese attack from Indochina would probably be a holding operation to divert Chinese forces, while the main drive would be along the Burma Road. The capture of Kunming from this direction, which is not regarded as impossible, would then probably nullify the Chinese resistance in eastern Yunnan, as Japanese forces could thrust down the railway or roadbed from Kunming to complete a pincers movement against Chinese troops in that area.