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41. On the assumption, however, that circumstances do enable us to secure Turkish or Iranian co-operation against Russia or to infringe their territorial rights, the following are the military factors affecting Allied action against Caucasian oil supplies.

Áir attack.

42. The most vulnerable oil objectives in the Caucasus are the groups of refineries at Baku, Grozni and Batum, of which the first is by far the most important. We are advised that a refinery, once effectively destroyed, could not be repaired under nine months at least. The Russians are well aware of the vulnerability of their oil installations in the Caucasus, which are defended by large numbers of fighters and anti-aircraft weapons, though the efficacy of these defences, being Russian, is no doubt not so formidable as their numbers would suggest. There must however remain, in the absence of any experience of sustained air action against this scale of defence, some element of doubt whether the requisite wholesale destruction of all the refineries could be carried out.

43. A plan for the attack of these installations is now being worked out by the Air Staff in the Middle East, and is also under examination in the Air Ministry. It is at present estimated that the destruction of the principal refineries might be achieved by sustained operations over a period of several weeks by a force of not less than three bomber squadrons. In the event of hostilities with Russia, it would be desirable to undertake these operations as soon as circum- stances permit, since delay would give the Russians an opportunity of improving their defences, possibly even by the addition of German fighters.

44. The plan involves operations at long range over difficult and mountainous country. The only squadrons now in the Middle East with the necessary range are three squadrons of Wellesleys. These are not suited for action by day against the scale of defence to be anticipated, though some of them might be used to supplement at night the activities of squadrons working by day. The operations must, therefore, in the main be undertaken by Mark IV Blenheims, for which we can provide the tropical equipment required to enable them to operate in this part of the world. Three squadrons of this type would, therefore, have to be provided in the Middle East, complete with the necessary reserves to enable them to replace wastage.

45. It is essential that the implications of such a course of action should be clearly understood. Whether the Mark IV Blenheims are used to re-equip Mark I Blenheim squadrons now in the Middle East, or to reinforce the Middle East Command, the fact remains that the necessary aircraft and equipment can only be found from home resources. If the aircraft of three complete squadrons with the necessary reserves were drawn from the United Kingdom, the result, taken in conjunction with certain operations now under preparation, would be that practically all the home-based medium bombers now available to support the British Air Forces in France in the event of a German offensive through the Low Countries, or for any of our major air plans, would be otherwise employed.

Moreover, recent demands on our resources of skilled personnel and equipment have already set back, by several weeks at least, the progress of other important developments, such as the completion of the four long-range fighter squadrons for trade protection, the formation of new fighter squadrons to meet new commitments such as the defence of Scapa, the expansion of the bomber force and the re-equipment of existing squadrons with the most modern types. The fact must be faced that the despatch of three more squadrons to the Middle East will inevitably retard these important Home Defence developments still further. Nevertheless, if these disadvantages were accepted, three squadrons of Mark IV Blenheims could be provided from the metropolitan force, and-if the necessary preparations were put in hand at once- should be ready to operate from bases in Northern Iraq or Syria by the end of April. This period of preparation could be progressively reduced in the coming months. Any addition to the number of squadrons detailed for the operations, though it would be desirable in relation to the Caucasus plan, would accentuate the disadvantages described above, and could not be effected without further considerable delay.

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