Background

The item below is from the UK National Archives. It is an ULTRA/Enigma intercept. There are some assumptions in there which I’d happily correct, if someone knows better.

1. Operational Units
   
   1. Single-engine fighters: 19 fighter squadrons with 450 – 500 Tomahawks and Hurricanes, of which at the moment 390 are in the front area, according to air photography. [actual: 17.5 squadrons and one flight of Fleet Air Arm Martlets, with another 4 more forming, 280 operational with another 394 operational in 14 days – so this is a serious over-estimate by German intelligence]
      
   2. Heavy fighters: 3 squadrons with 60 Beaufighters, at least 1 squadron of these in the front area. [actual: 1 squadron with 16 aircraft, with another 3 forming, and 8 more aircraft becoming operational in 14 days – another serious overestimate]
      
   3. Day bombers: 12 squadrons with 200-250 Maylands and Blenheims, of which at the moment about 170 are in the front area according to photography. 1 squadron, equipped with Boeing Fortress I aircraft, probably being formed in the Delta area. The greater fighting value of the Maryland as opposed to the Blenheim permits its employment as an auxiliary heavy fighter: low-level attacks and, above all, attacks on transport aircraft have frequently been successfully carried out (armament: 4 fixed MG’s firing forwards, 2 firing backwards, and in addition one moveable twin MG firing upwards and one firing backwards: this has been established from captured aircraft.) [actual: 9 squadrons of light bombers with 2 squadrons and 1 flight of Maryland/Blenheim reconnaissance, with a total of 144 bombers and 36 reconnaissance operational; none forming, and another 193 light bombers becoming operational in 14 days. 3 Fortresses only, which were on special assignment. Also half a squadron of Boston III active with 8 planes, with the half forming, and 15 Boston III to become active in 14 days – this is a reasonably accurate estimate; regarding the use of the Maryland as a heavy fighter, it rather appears to me that (with one exception I am aware of), Blenheims served in this role]
      
   4. Night bombers: 5 squadrons with 125 Wellingtons, night attacks on Cyrenaica are carried out every night, aircraft starting from Suez Canal area, with advanced landing grounds in the Western Desert (gliding attacks and flare-dropping carried out). [actual 5 squadrons with 100 planes operational and another 22 to become operational in 14 days no squadrons forming – this is an almost perfect estimate flare dropping however was carried out by Fleet Air Arm Albacores, which are not included in this strength report]
      
   5. Transport aircraft: 2 transport squadrons with 25 Bombays and/or Valentias and 20 Lockheeds. 6 Bombays were employed on night 16-17/11 to drop parachute sabotage detachment in Cyrenaica (this is confirmed by the shooting down of one aircraft and the papers recovered from it). [actual 2 squadrons with 24 Bombays/Valentias operational and another 4 to become operational in 14 days, no squadrons forming; 1 squadron with no Lockheed/Douglas active, and another one forming, with 16 planes to become operational in 14 days – again a very reasonable estimate)
      
   6. The shortage of personnel existing after the units have been brought up to strength as regards material seem to have been overcome. It must be assumed that there exist strong reserves in aircraft parks for fighter and bomber units, since there has been a constant flow of supplies by air to Africa (U.S.A. material) and via Mediterranean (English material) (cf. air photograph of aerodrome 25 km west of Hedouan. [this is a correct interpretation of the situation]
      
2. Scale of Effort
   

   Night bomber units since 1/9/41, regularly at about 15 per cent daily. It is probable that with the increased scale of effort since early November the maximum possibilities of these units have been reached. On the other hand fighter and day bomber units have been carefully withheld up to the beginning of the month. Their present increased scale of effort is normal, having regard to the situation (scale of effort since … at the moment reaches at the most 25 per cent of the actual strength). It thus appears that scale of effort in present form is possible for some time ahead, and may even rise for a while.
   

Vickers Wellington medium bomber, date/location unknown, IWM. These planes were the mainstay of the night bombing offensive against Axis airfields, ports, and population centers in Libya and Southern Italy in 1941.

Comments

Actual scale of effort:

• Assuming 2 sorties per day for single-engine fighters, the capacity usage was 10% in this week, although that is a big if, since 521 of the 673 (plus 18 Hurricane recce and 16 Hurribomber sorties) sorties of all fighters are unspecified and could include Beaufighters and Blenheims. For the Beaufighters (assumed 1 sortie), usage was 26% of capacity, 29 sorties.
  
• Assuming 2 sorties per day for Blenheims and Marylands, the effort was about 9%, 185 sorties (plus 5 Blenheim fighter sorties) with 144 operational planes, but there are also 64 unspecified bomber sorties, some of which will be Fortresses, some others Wellingtons and light bombers.
  
• For the reconnaissance Blenheims and Marylands, usage was only 7%, assuming one sortie per day as capacity. A total of 18 sorties was made. But there are another 23 unspecified sorties.
  
• Assuming (based on nothing but my own thoughts, if someone knows Luftwaffe capacity assumptions, please let me know) total capacity is 1 sortie per day for the Wellingtons, the effort in this week was about 21%, at 148 sorties compared to 100 operational planes.
  
• For the transport fleet, utilization was also low, at 9% (assuming 1 sortie per day), 15 sorties of Bombays are recorded]
  

Analysis

The numbers appear to show a very strong focus on the initial gaining of air superiority. For example, in the following week, the Blenheims and Marylands had 265 sorties with unchanged operational numbers, a rate of 13%. Wellington sorties remained practically unchanged, while fighter sorties increased to 777 on unchanged numbers, or a rate of 20%. Unspecified bomber sorties tripled however, so the actual utilization was higher.
Compared to the Luftwaffe expectation, the Desert Air Force was operating at a low capacity rate, if the assumptions are correct. This is partially explained by the longer distance planes had to fly to get to their area of operations, I guess. But there are also questions raised e.g. by Australian Wing Cdr. Geddes in a special report, about the efficiency of the ground crews.