MARCH 31, 1941.
Comdr. Naval Base Defense Air Force,     Commanding General
Commander Patrol Wing TWO,               Hawaiian Air Force,
Naval Air Station,                       Fort Shafter, T. H.
Pearl Harbor, T. H.

Joint estimate covering Joint Army and Navy air action in the event of sudden hostile action against Oahu or Fleet Units in the Hawaiian area.

I. Summary of the Situation.

(a) Relations between the United States and Orange are strained, uncertain and varying.

(b) In the past Orange has never preceded hostile actions by a declaration of war.

(c) A successful, sudden raid, against our ships and Naval installations on Oahu might prevent effective offensive action by our forces in the Western Pacific for a long period.

(d) A strong part of our fleet is now constantly at sea in the operating areas organized to take prompt offensive action against any surface or submarine force which initiates hostile action.

(e) It appears possible that Orange submarines and/or an Orange fast raiding force might arrive in Hawaiian waters with no prior warning from our intelligence service.

II. Survey of opposing Strengths.

(a) Orange might send into this area one or more submarines and/or one or more fast raiding forces composed of carriers supported by fast cruisers. For such action she is known to have eight carriers, seven of which are reported to be capable of 25 knots or over and four of which are rated at 30 knots or better. Two of the carriers are converted capital ships, armoured and armed with 10-8" guns each and reported to have heavy AA batteries. Two others are small (7000 treaty tons) and limited to 25 knots. Exact information on numbers and characteristics of the aircraft carried by these ships is not available. However the best estimate at present available is that the small carriers can accommodate from 20 to 30 planes and the large ones about 60. Probably the best assumption is that carrier complements are normally about equally divided between fighter and bomber types. Lacking any information as to range and armament of planes we must assume that they are at least the equal of our similar types. There probably exist at least 12 eight inch gun and at least 12 six inch gun fast modern cruisers which would be suitable supports. Jane's Fighting Ships (1939) shows over forty submarines which are easily capable of projection into this area. An Orange surface raiding force would be far removed from their base and would almost surely be inferior in gun power to our surface forces operating at sea in the Hawaiian area.

(b) The most difficult situation for us to meet would be when several of the above elements were present and closely coordinated their actions. The shore-based air force available to us in a constantly varying quantity which is being periodically augmented by reinforcements from the mainland and which also varies as fleet units are shifted. Under existing conditions about one-half of the planes present can be maintained in a condition of material readiness for flight. The aircraft at present available in Hawaii are inadequate to maintain, for any extended period, from bases on Oahu, a patrol extensive enough to insure that an air attack from an Orange carrier cannot arrive over Oahu as a complete surprise. The projected outlying bases are not yet in condition to support sustained operations. Patrol planes are of particular value for long range scouting at sea and are the type now available in this area best suited for this work. If present planes are used to bomb well defended ship objectives the number available for future use will probably be seriously depleted. In view of the continuing need for long range overseas scouting in this area the missions of those planes for operations as contemplated in this estimate should be scouting. Certain aircraft of the Utility Wing although not designed for combatant work, can be used to advantage in augmenting the scouting of patrol planes. Other types of aircraft in general, can perform functions that accord with their type.

III. Possible enemy action.

(a) A declaration of war might be preceded by:

    1. A surprise submarine attack on-ships in the operating area.
    2. A surprise attack on OAHU including ships and installations in
       Pearl Harbor.
    3. A combination of these two.

(b) It appears that the most likely and dangerous form of attack on OAHU would be an air attack. It is believed that at present such an attack would

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most likely be launched from one or more carriers which would probably approach inside of three hundred miles.

(c) A single attack might or might not indicate the presence of more submarines or more planes awaiting to attack after defending aircraft have been drawn away by the original thrust.

(d) Any single submarine attack might indicate the presence of a considerable undiscovered surface force probably composed of fast ships accompanied by a carrier.

(e) In a dawn air attack there is a high probability that it could be delivered as a complete surprise in spite of any patrols we might be using and that it might find us in a condition of readiness under which pursuit would be slow to start, also it might be successful as a diversion to draw attention away from a second attacking force. The major disadvantage would be that we could have all day to find and attack the carrier. A dusk attack would have the advantage that the carrier could use the night for escape and might not be located the next day near enough for us to make a successful air attack. The disadvantage would be that it would spend the day of the attack approaching the islands and might be observed. Under the existing conditions this might not be a serious disadvantage for until an overt act has been committed we probably will take no offensive action and the only thing that would be lost would be complete surprise. Midday attacks have all the disadvantages and none of the advantages of the above. After hostilities have commenced, a night attack would offer certain advantages but as an initial crippling blow a dawn or dusk attack would probably be no more hazardous and would have a better chance for accomplishing a large success. Submarine attacks could be coordinated with any air attack.

IV. Action open to us:

(a) Run daily patrols as far as possible to seaward through 360 degrees to reduce the probabilities of surface or air surprise. This would be desirable but can only be effectively maintained with present personnel and material for a very short period and as a practicable measure cannot, therefore, be undertaken unless other intelligence indicates that a surface raid is probable within rather narrow time limits.

(b) In the event of any form of surprise attack either on ships in the operating areas or on the islands:

1. Immediate search of all sea areas within reach to determine the location of hostile surface craft and whether or not more than one group is present.

2. Immediate arming and preparation of the maximum possible bombing force and its dispatch for attack when information is available.

(c) In the event of an air attack on OAHU, in addition to (b) above:

1. The immediate dispatch of all aircraft suitable for aerial combat to intercept the attackers.

2. The prompt identification of the attackers as either carrier or long range shore based aircraft.

3. The prompt dispatch of fast aircraft to follow carrier type raiders back to their carriers.

(d) In the event of a submarine attack on ships in the operating area in addition to (b) above:

1. Hold pursuit and fighter aircraft in condition of immediate readiness to counter a possible air raid until search proves that none is imminent.

2. Dispatch armed shore based fleet aircraft to relieve planes in the air over the attack area.

3. Establish a station patrol by patrol planes two hundred twenty mile radius from scene of attack at one hour before daylight of next succeeding daylight period.

(e) None of the above actions can be initiated by our forces until an attack is known to be imminent or has occurred. On the other hand, when an attack develops time will probably be vital and our actions must start with a minimum of delay. It therefore appears that task forces should be organized now, missions assigned, conditions of readiness defined and detailed plans prepared so that coordinated immediate action can be taken promptly by all elements when one of the visualized emergencies arises. To provide most effectively for the necessary immediate action, the following joint task units will be required:

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1. Search Unit.

2. Attack Unit.

3. Air Combat Unit.

Carrier scouts, army reconnaissance and patrol planes can be employed with very widely varying effectiveness, either for search or attack. Under varying conditions some shifts of units between the search and attack groups may be desirable. Also, the accomplishment of these two tasks must be closely coordinated and therefore these two groups should be controlled by the same task group commander.

V. Decisions:

1. This force will locate and attack forces initiating hostile actions against OAHU or fleet units in order to prevent or minimize damage to our forces from a surprise attack and to obtain information upon which to base coordinated retaliatory measures

2. Subsidiary decisions. In order to be in all respects prepared to promptly execute the above decision:

(a) Establish a task organization as follows by the issue of a joint air operation plan:

1. Search and Attack Group (Commander Naval Base Defense Air Force (Commander Patrol Wing TWO)). The following units in accordance with current conditions of readiness:

 Patrol squadrons.
Shore-based VO-VS units.
Shore-based carrier VB and VT squadrons.
Shore-based carrier VS planes not assigned to the air combat group. Shore-based Marine VS and VB squadrons.
Army bombardment squadrons.
Army reconnaissance squadrons.
Navy Utility Squadrons.

2. Air Combat group (Commander Hawaiian Air Force) The following units in accordance with current conditions of readiness:

 Army pursuit squadrons.
Shore-based carrier VF squadrons.
Shore-based Marine VF squadrons.
One division of shore-based carrier VS planes. (Primarily for trailing aircraft).

(b) Assign missions to the above groups as follows:

1. Search and Attack Group. Locate, report and track all hostile surface units in position to take or threaten hostile action. Destroy hostile ships by air attack. Priority of targets: (1) carriers (2) large supporting ships. If choice of location is presented priority should be given to: (1) carrier involved in attack (2) vessels beyond reach of our surface vessel interception.

2. Air Combat Group. Intercept and destroy hostile aircraft. Identify and report type of attacking aircraft. Trail attacking carrier type planes to carrier and report location to commander search and attack group. As a secondary mission support search and attack group upon request.

(c) Provide a means for quickly starting all required action under this plan when:

    (a) An air attack occurs on OAHU.
    (b) Information is received from any source that indicates at attack
        is probable.
    (c) Information is received that an attack has been made on fleet

(d) Define conditions of readiness for use with this plan as follows:

Conditions of readiness shall be prescribed by a combination of a letter and number from the tables below. The letter indicating the part of a unit in a condition of material readiness for its assigned task and the number indicating the degree of readiness prescribed for that part.


A. All assigned operating aircraft available and ready for a task.

B. One-half of all aircraft of each functional type available and ready for a task.

C. Approximately one quarter of all aircraft of each functional type available and ready for a task.

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D. Approximately one-eighth of all aircraft of each functional type available and ready for a task.

E. All aircraft conducting routine operations, none ready for the purposes of this plan.


1. For pursuit and VF types-four minutes. Types other than fighters-fifteen minutes.

2 All types-30 minutes.

3 All types-one hour.

4. All types-two hours.

5. All types-four hours.

The armament and fuel load for each type under the above conditions of readiness are dependent upon the tasks assigned in contributory plans and orders and will be prescribed therein.

(e) Establish a procedure whereby the conditions of readiness to be maintained by each unit is at all times prescribed by the Senior officers present of the Army and Navy as a result of all information currently available to them. In using the above conditions it should be noted that: CONDITION A-1 requires a preparation period of reduced operations and can be maintained for only a short time as it is an all hands condition. CONDITIONS B-1 and B-2 require watch and watch for all personnel and personnel fitness for air action will decrease rapidly if they are maintained too long. Any condition 1, 2, or 3 will curtail essential expansion training work. CONDITIONS C, or D, 4 or 5 can be maintained without unduly curtailing normal training work.

V. Decisions:

(f) In order to perfect fundamental communications by use and to insure that prospective Task Group Commanders at all times know the forces immediately available to them for use, under the plan above, in case of a sudden emergency, provide, for daily dispatch readiness reports as of the end of normal daily flying from all units to their prospective task force commander. These reports to state:

(a) Number of planes in the unit by functional types such as bomber, fighter, etc.

(b) Number of each type in commission for flight and their degree of readiness as defined above.

(g) After the joint air operations plan under subsidiary decision (a) above has been issued, the task group commanders designated therein will prepare detailed contributory plans for their groups to cover the various probable situations requiring quick action in order that the desired immediate action in an emergency can be initiated with no further written orders. To assist in this work the following temporary details will be made:

(a) By Commander Naval Base Defense Air Force (Commander Patrol Wing TWO) an officer experienced in VF and VS operations and planning to assist the Commander of Air Combat Group.

(b) By the Commander Hawaiian Air Force: an officer experienced in Army bombardment and reconnaissance operations and planning to assist the Commander of the Search and Attack Group.

                                 (Signed) F. L. Martin,
                                          F. L. MARTIN
                                       Major General, U. S. Army,
                                    Commanding Hawaiian Air Force.
                                 (Signed) P. N. L. Bellinger,
                                          P. N. L. BELLINGER,
                                       Rear Admiral, U. S. Navy,
                                  Commander Naval Base Defense Air Force,
                                     (Commander Patrol Wing TWO).