I. B. 148-1
November 13, 1941.
Memorandum for the Chief of Staff:
Subject: Possible Japanese Drive into Yunnan.
1. Reference is made to memorandum of this Division to the Chief of Staff, I. B. 148, November 1, 1941, subject: Possible Japanese Drive into Yunnan. In this memorandum emphasis was placed on the principal avenue of advance, Laokai-Kunming. Since its submission the question has been raised of the possibility of a Japanese advance against Kunming and the Burma road through Kwangsi Province, in conjunction with a penetration up the normal avenue of the Yunnan railroad, Laokai-Mengtze-Kunming.
2. The axis of the route through Kwangsi is the course of the Yu river, 150 miles northeast of the Yunnan railroad and roughly parallel to it. (See Map, Tab A.) This river rises in the mountains of eastern Yunnan and flows through southwest Kwangsi Province to its confluence with the West River near Nanning. It is navigable for river junks as far west as Poseh. To make use of this corridor the Japanese would have to move north from Hanoi to Caobang, thence across the Chinese border to the vicinity of Poseh, whence they could launch their attack up the Yunnan escarpment toward Kwangnan on the plateau. 150 miles southeast of Kunming.
This would be an even more difficult operation than a direct attack along the Yunnan railway line, since the supply problem would be enormous. From Caobang a fair road for light motor traffic runs 185 miles north to Poseh. Most bridges on this route have a capacity of only 1 1/2 tons. Also it is probable that since the Japanese occupation of Indo-China, the Chinese have destroyed the road near the border.
Poseh can also be reached by the Hanoi-Langson-Nanning road, and thence northwest via Wuming and the Yu valley. Somewhat better roads exist on this route but the distance from Langson to Poseh is about 260 miles, as compared with 185 from Caobang to Poseh. Here also, the Chinese have demolished the highways near the border, and also the railway line which was under construction before the Japanese occupation of Nanning in 1940.
Arrived at Poseh the Japanese would be confronted with practically the same difficult terrain conditions as at Laokai, on the frontier Poseh has an elevation of 525 feet; Kwangnan, 4,515. The air distance between the two is approximately 100 miles, and there are no motor roads in existence. (The Chinese have been surveying a highway from Kaihua, east of Mengtze on the Yunnan railway, through Kwangnan to Poseh, but latest reports indicate no actual construction on this route.) The terrain is almost as rugged as that north of Laokai.
The only apparent reason for use of this route would be in the event that the Japanese plan of campaign called for a "pincers" movement on Kunming. However, it would not be a true envelopment as initially it would be directed against Chinese forces not allotted to the defense of Kunming. Absence of lateral communication inside China would be a serious handicap to such an operation, to say nothing of the long line of communications through a hostile territory.
3. a. For defense against a movement through Kwangsi Province, there are available in the Fourth War Zone (Kwangsi and western Kwangtung) the following troops:
16th Group Army: 31st Army Corps of 2 divisions: 46th Army Corps of 2 divisions.
35th Group Army: 64th Army Corps of 2 divisions.
These are regular troops, largely veterans from Kwangsi and adjacent areas, of excellent fighting ability. The Zone Commander is Chang Fa-kuei, a very capable officer of long experience.
b. The Chinese lack artillery, are very short of ammunition, both artillery and small arms, and to all practical purposes are devoid of an air force.
4. An attack on Kunming through Kwangsi Province is only conceivable in conjunction with an advance up the Yunnan railway. It is estimated that this would require at least an additional five Japanese divisions, or a minimum total task force of 10 divisions.
5. It is estimated that there are now available in Indo-China for an expedition against Kunming a maximum of 40,000 troops, probably less. At least 160,000 troops would have to be brought into Indo-China through Haiphong for a double envelopment, and at least 60,000 for a single direct attack. ONI estimates the capacity of this port at 2,000 fully equipped troops per day. On this basis, under the most favorable circumstances, at least one month would he required to concentrate a sufficient force for the direct attack up the Yunnan railway. Between two and three months would he required to make the concentration for a double attack up the railway and up the Yu river valley.
6. The rate of Japanese advance on Kunming once the border is crossed, would depend on the degree of Chinese resistance, especially in the defense of the extremely rugged terrain between the Indo-Chinese and Yu river plains and the Yunnan plateau.
7. A Japanese offensive into Yunnan from Indo-China would be an extremely difficult operation but if it were successful in closing the supply route from Burma it would be a serious blow to China's power and will to resist. In this connection it is interesting to note that the British War Office concludes that such an
offensive would be rendered "most difficult" by reason of the supply problem alone, while the French Military Attache at Tokyo ridicules any idea of an attack on Yunnan from Indo-China.
Brigadier General U. S. Army
Acting Assistant Chief of Staff, G-2.
Tab A. 
The President Mr. Lauchlin Currie
Secretary of War Division of Defense Aid Reports
Secretary of State Director of Naval Intelligence
Under Secretary of War Assistant Chief of Staff, W. P. D.
Assistant Secretary of War G. H. Q.
Assistant Secretary of War Chief of the Air Corps
for Air Air Corps
Chief of Staff General Embick
Coordinator of Information
Chief of the Army Air Forces
(EXHIBITS OF THE JOINT COMMITTEE, PHA, PT. 14, EXHIBIT NO. 33 MILITARY INTELLIGENCE ESTIMATES PREPARED BY G-2, WAR DEPARTMENT)