‘Operation Unthinkable’

Report from the British Military leaders to Prime Minister Winston Churchill on the chances of ‘Operation Unthinkable’ -a surprise attack on the USSR, 22 May 1945 (Catalogue ref: CAB 120/691)




  1. We have examined Operation Unthinkable. As instructed, we have taken the following assumptions on which to base our examination:
    1. The undertaking has the full support of public opinion in the British Empire and the United States and consequently, the morale of British and American troops continues high.
    2. Great Britain and the United States have full assistance from the Polish armed forces and can count upon the use of German manpower and what remains of German industrial capacity.
    3. No credit is taken for assistance from the forces of the other Western Powers, although any bases in their territory, or other facilities which may be required, are made available
    4. Russia allies herself with Japan.
    5. The date for the opening of hostilities is 1st July, 1945.
    6. Redeployment and release schemes continue till 1st July and then stop.

Owing to the special need for secrecy, the normal staff in Service Ministries have not been consulted.


  1. The overall or political object is to impose upon Russia the will of the United States and British Empire.

Even though ‘the will’ of these two countries may be defined as no more than a square deal for Poland, that does not necessarily limit the military commitment. A quick success might induce the Russians to submit to our will at least for the time being; but it might not. That is for the Russians to decide. If they want total war, they are in a position to have it.

  1. The only way we can achieve our object with certainty and lasting results is by victory in a total war but in view of what we have said in paragraph 2 above, on the possibility of quick success, we have thought it right to consider the problem on two hypotheses:-
    1. That a total war is necessary, and on this hypothesis we have examined our chances of success.
    2. That the political appreciation is that a quick success would suffice to gain our political object and that the continuing commitment need not concern us.


  1. Apart from the chances of revolution in the USSR and the political collapse of the present regime – on which we are not competent to express an opinion – the elimination of Russia could only be achieved as a result of:
    1. the occupation of such areas of metropolitan Russia that the war making capacity of the country would be reduced to a point at which further resistance became impossible.
    2. Such a decisive defeat of the Russian forces in the field as to render it impossible for the USSR to continue the war.

Occupation of Vital Areas of Russia

  1. The situation might develop in such a way that Russians succeeded in withdrawing without suffering a decisive defeat. They would then presumably adopt the tactics which they had employed so successfully against the Germans and in previous wars of making use of the immense distances with which their territory provides them. In 1941 the Germans reached the Moscow area, the Volga and the Caucasus, but the technique of factory evacuation, combined with the development of new resources and Allied assistance, enabled the U.S.S.R. to continued fighting.
  2. There was virtually no limit to the distance to which it would be necessary for the Allies to penetrate into Russia in order to render further resistance impossible. It is far as, or as quickly as, the Germans in 1942 and this penetration no decisive result.

Decisive Defeat of the Russian Forces

  1. Details of the present strengths and dispositions of the Russian and Allied forces are given in Annexes II and III and illustrated maps A and B. The existing balance of strength in Central Europe, where the Russians enjoy a superiority of approximately three to one, makes it most unlikely that the Allies could achieve a complete and decisive victory in that area in present circumstances. Although Allied organisation is better, equipment slightly better and morale higher, the Russians have proved themselves formidable opponents of the Germans. They have competent commanders, adequate equipment and an organisation which though possibly inferior by our standards, has stood the test. On the other hand, only about one third of their divisions are of a high standard, the others being considerably inferior and with overall mobility well below that of the Allies.
  2. To achieve the decisive defeat of Russia in a total war would require, in particular, the mobilisation of manpower to counteract their present enormous manpower resources. This is a very long term project and would involve:-
    • The deployment in Europe of a large proportion of the vast resources of the United States.
    • The re-equipment and re-organisation of German manpower and of all the Western Allies.



  1. We conclude that:-
    • That if our political object is to be achieved with any certainty and with lasting results, the defeat of Russia in a total war will be necessary.
    • The result of a total war with Russia is not possible to forecast, but the one thing certain is that to win it would take us a very long time.


  1. It might, however, be considered, as result of a political appreciation, that a quick and limited military success would result in Russia accepting out terms.
  2. Before a decision to open hostilities were made, full account would have to taken of the following:-
  • If this appreciation is wrong and the attainment of whatever limited objective we may set ourselves does not cause Russia to submit to our terms, we may, in fact, be committed to a total war.
  • It will not be possible to limit hostilities to any particular area. While we are in progress, therefore, we must envisage a world-wide struggle.
  • Even if all goes according to plan, we shall not have achieved, from the military point of view, a lasting result. The military power of Russia will not be broken and it will be open to her to recommence the conflict at any time she sees fit.
  1. Assuming, however, that it is decided to risk military action on a limited basis, accepting the dangers set out above, we have examined what action we could take in order to inflict such a blow upon the Russians as would cause them to accept our terms, even though they would not have been decisively defeated and, from the military point of view, would still be capable of continuing the struggle.
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