I. B. 93

                                                           JULY 7, 1941.
Memorandum for the Chief of Staff: 
Subject: Estimate of the Eastern Siberian Situation. 

1. Eastern Siberia, that is to say, the region lying between Lake Baikal and the Pacific Ocean, is a distinct entity quite separate from the other portions of Siberia and old Russia. Remote and lying behind the Lake Baikal-Lena River barrier its terrain is not that of the swampy railway-dominated wilderness of Central Siberia but admits of normal troop deployments and operations. It is economically distinct in its mineral deposits, its fisheries and its self-contained economy. Politically and psychologically it is distinct, little changed from Czarist days. It thinks for itself and will act for itself first, and for the rest of Russia only secondarily.

2. It is quite within the range of possibility that should Stalin and his communist regime be driven out of Russia the retreat would be to this Far Eastern Region.

3. The Russian forces in this region are a homogenous army of 51 divisions, 2,500 tanks, 1,600 airplanes, 94 submarines and 220 coastal boats as opposed to Japanese forces of 10 divisions, 1,000 tanks, 300 airplanes and a balanced Fleet. The distribution and relationships of these forces are shown on the accompanying map.

4. This region is potentially a sufficiently homogeneous one to constitute an effective buffer-state between the Bering Sea Region and the Axis powers, German or Japanese.

5. A German occupation of Eastern Siberia would require the employment of combat forces of such size as to be very difficult, if not impracticable, of accomplishment at the end of a 2,000 mile single railway system. The Axis allocation of this region, therefore, to Japan is the more likely procedure, though supported perhaps by German air power and political pressures.

6. With the memory of the Russian superior fighting ability demonstrated in the border affrays of 1938-39, the Japanese are unlikely to take aggressive action against Eastern Siberian land forces. This is confirmed by evidence from other and highly authoritative sources of reluctance to change from their present southern orientation to a northern one. This, however, does not preclude increasing Japanese pressures through Outer Mongolia towards Verkhneudinsk, of naval blockades of the entrances to the Sea of Japan, the Sea of Okhotsk and possibly Bering Sea.

                                               /s/ C. H. Mason,
                                                   C. H. MASON
                                          Colonel of Infantry, G. S. C., 
                                            Chief, Intelligence Branch. 
   The President 
   Secretary of War 
   Chief of Staff 
   War Plans Division 
   Office of Naval Intelligence 
   G. H. Q.
   General Embick 
   Mr. McCloy (Record Section)