The Orange Minor Maneuvers of 1931 and 1932, like the 1929 Maneuvers before them and the 1934 and 1935 Maneuvers after them, were comparable with our own “U.S. Fleet Problems.” The China Patrol, vessels in the Navy Yard, and ships on detached duty did not participate.

The First Fleet was opposed to the Second Fleet in each exercise. They assisted our reconstruction of the “Blue Book” and gave us intercept material in the so called “minor” cryptographic systems. They disclosed that the complement of a Japanese naval vessel war from 150% to 200% that of an American vessel of the same size. Also that, in the matter of Training and preparation for war, the Japanese Navy was at least equal to our own.

The 1933 Maneuvers followed the magnitude and general pattern of the 1930 Grand Maneuvers and confirmed our belief that they were a rehearsal of war plans.  We had much more intercept material to work on because our operators were more numerous and experienced, and the maneuvers lasted longer, so the information, was considerably greater.  The lessons of 1930 were not wasted on the R.I. Organization and plans were made, well in advance, for the secret participation of the Asiatic R.I. Units in the 1933 Maneuvers.  At that time, the Asiatic R.I. Organization consisted of one officer and 30 men, all of whom covered the 1930 Maneuvers.  The Asiatic R.I. personnel were scattered among four widely separated stations.  This permitted a greater amount and variety of intercepted messages but made coordination difficult and entailed serious delays in getting intercept logs to the points where they could be used.


The Asiatic R.I. Officer (LT Winger) attempted to combine a simulation of war conditions with the maximum interception of Japanese naval messages, and made special effort to get fleet traffic on enemy frequencies by means of a ship cruising the prospective theatre of operations.  The GOLD STAR’S “health cruise” was scheduled to put her in Manila just prior to the maneuvers and return to Guam during the maneuvers.  At Cavite the ship’s radio operators where taken off and replaced by four R.I. operators from Olongapo.  Additional receivers and I.F. direction finder were installed on the GOLD STAR. However, on the only occasion that the GOLD STAR was in a position to perform any intercept work which would not be done at the shore station, the Japanese laid down obliterative interference, and, to quote the GOLD STAR report:

“The results were so thorough in effect that is was impossible for the GOLD STAR to copy solid a single message transmitted during the period from about 0900 to 1700, 13 August.”

It is evident that the Japanese were fairly well informed as to our intercept activities on the Asiatic Station, which were the subject of table gossip in Manila.  Due to effective counter measures on the part of the Japanese, the operators on the GOLD STAR accomplished nothing and would have been more useful if they had remained at Olongapo.

The Asiatic Fleet Radio Intelligence Officer remained aboard the fleet flagship at Tsingtoa, and, while R.I. estimates from the intercept stations were occasionally forwarded by radio, the intercept logs for the most part did not reach him until after the conclusion of the maneuvers.  This delay was “constructively” cancelled in his analysis.  Due to lack of clerical assistance, LT Wenger did not attempt the decryption of problem traffic (except for one batch of submarine messages) but gave a full-scale test to our theories of “traffic analysis”.  The “Blue Book” had been solved and “reconstructed” to better than “50% readability” by that time.

Due to the foregoing circumstances, our radio intelligence study of the 1933 Maneuvers consisted of three phases; manly: 

(1) Interception and “spot” analysis by enlisted personnel at the intercept stations. “Hot information” was forwarded by radio to CINCAF.

(2) Traffic analysis (in retrospect) by Asiatic R.I. Officer aboard the fleet flagship.  This continued for six months.  Decryption was not undertaken in order to test how much information could be obtained by “methods short of cryptanalysis” and how accurate this information could be.

(3) Decryption of the messages, verification of the “traffic analysis” and analysis of the maneuvers back at the Navy Department.  This continued for a period of three years, until we had extracted every possible bit of information from the intercepted message.

CINCAF’s original report, dated 7 March 1934, consisted of 115 pages.  Notations indicate that it was seen by:

CAPT Hooper (D.N.C)
REAR ADM Bryant (D.W.P)
REAR ADM Taussig (Asst C.N.O)

The D.N.C.’s supplementary report, dated 30 April 1937, consisted of 120 pages.  It was routed to C.N.O via the D.N.I, and was undoubtedly referred to the War Plans Division, but there is no record of this fact.

From the Japanese point of view the maneuvers were divided into four distinct phases; namely: (1) Mobilization – 17 May to 12 July. (2) Strategic Period – 13 July to 14 August.  (3) Tactical Period – 15-19 19 August.  (4) Critique and Fleet Review by the Emperor – 21-25 August.

The mobilization was heralded by the sudden creation of the Forth Fleet, consisting mostly of older vessels which had been in a reserve status or undergoing modernization.  The Fourth Fleet took over the stations and functions performed by the First Fleet in the 1930 Maneuvers and was often referred to as the “Home Defense Fleet”.  (This released the First Fleet for more aggressive functions.)  During the tactical phase of the maneuvers the Forth Fleet represented the entire Combined Fleet.  The Fourth Fleet remained in existence after these maneuvers, although changing somewhat in composition, this marking another step in the mobilization of the Japanese Navy for an “all-out” war.  In fact, the only other radical change in the organization of the Japanese Navy was the creation of the Fifth Fleet, stationed in the Kurile Islands, in the early summer of 1941.

In connection with the foregoing, the following is quoted from CINCAF’s secret letter CF 283 dated 7 March 1934:


“The first indications (of mobilization) appeared in February (1933).  At this time secret calls of a new type were heard.  Then in March the Guam unit began to notice a sudden change in the operating ability of Orange radiomen of the primary stations at Tokyo and Sasebo.  It soon became obvious that a number of new and inexperienced operators had been placed upon the circuits.  On 17 May both Olongapo and Guam began to detect changes in the normal fleet organization.  The names of certain units of the First and Second Fleets were changed and a new Fleet designated the “Fourth Fleet” came into being.  By the middle of June, Guam was able to give an extraordinarily accurate picture of the entire reorganization of all Orange naval forces, the most significant change being that many ships ordinarily held in reserve, were now in active service.

By L. F. Safford, Captain, USN