Operation Unthinkable

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Operation Unthinkable
Part of the end of World War II in Europe
Date1 July 1945 (projected).
Central and Eastern Europe.
Status Hypothetical British plans; rejected as impossible and never carried out.
 United States
 United Kingdom
Merchant flag of Germany (1946–1949).svg Germany
Flag of Poland (1928–1980).svg Poland
Soviet Union Soviet Union
Commanders and leaders
Harry Truman
Dwight D. Eisenhower
Walter Bedell Smith
Omar Bradley
Jacob L. Devers
Hoyt Vandenberg
United Kingdom Winston Churchill
United Kingdom Arthur Tedder
United Kingdom Frederick E. Morgan
United Kingdom Humfrey Gale
United Kingdom James Robb
United Kingdom Bernard Montgomery
Soviet Union Joseph Stalin
Soviet Union Vyacheslav Molotov
Soviet Union Aleksandr Vasilevsky
Soviet Union Georgy Zhukov
Soviet Union Lavrenty Beria
Soviet Union Boris Shaposhnikov
Soviet Union Georgy Malenkov
Soviet Union Nikolai Kuznetsov
Soviet Union Aleksandr Novikov
Soviet Union Semyon Timoshenko

Ground units:
80 infantry divisions

  • 3,065,500 American
  • 1,295,200 British
  • 437,140 French
  • 217,420 Canadian
  • 62,520 other

6,411,636 (total)

Tanks and assault guns:
23 armoured divisions

22,200 (total)

Combat aircraft:

  • 14,845 American aircraft
  • 5,559 heavy bombers
  • 6,003 fighters

28,000 (total)

Tactical aircraft:

  • 3,480 US
  • 2,370 Commonwealth
  • 198 Polish

6,048 (total)

Strategic aircraft:

  • 1,008 US
  • 1,722 Commonwealth
  • 20 Polish

2,750 (total)

Ground units:
228 infantry divisions

  • 6,750,149
    (Operational forces)
  • 431,838
    (Stavka reserves)

7,181,987 (total)

Tanks and assault guns:
36 armoured divisions

12,657 (total)

Combat aircraft:

  • 8,078 fighters
  • 4,991 ground-attack
  • 4,878 bombers
  • 876 reconnaissance
  • 3,798 others
    (Operational forces)
  • 183 fighters
  • 173 ground-attack
  • 204 bombers
  • 64 reconnaissance
  • 377 others
    (Stavka reserves)

19,447 (total)
Casualties and losses
none none

Operation Unthinkable was the name given to two related possible future war plans by the British Chiefs of Staff against the Soviet Union in 1945. The plans were never approved or implemented. The creation of the plans was ordered by British Prime Minister Winston Churchill in May 1945 and developed by the British Armed Forces' Joint Planning Staff in May 1945 at the end of World War II in Europe.[1]

One plan assumed a surprise attack on the Soviet forces stationed in Germany to "impose the will of the Western Allies" on the Soviets. "The will" was qualified as "a square deal for Poland"[2], which probably meant enforcing the recently signed Yalta Agreement. The planners decided that without massive American help Britain would probably fail. The assessment, signed by the Chief of Army Staff on June 9, 1945, concluded: “It would be beyond our power to win a quick but limited success and we would be committed to a protracted war against heavy odds."[3] The code name was now reused instead for a second plan, which was a defensive scenario in which the British were to defend against a Soviet drive towards the North Sea and the Atlantic following the withdrawal of the American forces from the Continent. At no time was either plan shared with the United States or anyone else. When the Labour Party came to power in July 1945 it ignored the draft plan.

The study became the first Cold War-era contingency plan for war with the Soviet Union.[4] Both plans were highly secret and were not made public until 1998[5] although a British spy for the Soviets, Guy Burgess, had passed on some details at the time.[6]



The initial primary goal of the operation was declared as "to impose upon Russia the will of the United States and the 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".[2] (The Soviet Union is referred to as "Russia" throughout the document, a metonym that was common in the West throughout the Cold War.)

The chiefs of staff were concerned that given the enormous size of Soviet forces deployed in Europe at the end of the war and the perception that the Soviet leader Joseph Stalin was unreliable, there was a Soviet threat to Western Europe. The Soviet Union had yet to launch its attack on Japanese forces and so one assumption in the report was that the Soviet Union would instead ally with Japan if the Western Allies commenced hostilities.

The hypothetical date for the start of the Allied invasion of Soviet-held Europe was scheduled for 1 July 1945, four days before the UK general election.[7] The plan assumed a surprise attack by up to 47 British and American divisions in the area of Dresden, in the middle of Soviet lines.[7] That represented almost half of the roughly 100 divisions available to the British, American and Canadian headquarters at that time.[5]

The plan was taken by the British Chiefs of Staff Committee as militarily unfeasible because of to an anticipated 2.5 to 1 superiority in divisions of Soviet land forces in Europe and the Middle East by 1 July, where the conflict was projected to take place.[8] Most of any offensive operation would have been undertaken by American and British forces, as well as Polish forces and up to 10 divisions of the former German Wehrmacht, remobilised from POW status. Any quick success would be caused by surprise alone. If a quick success could not be obtained before the onset of winter, the assessment was that the Allies would be committed to a protracted total war. In the report of 22 May 1945, an offensive operation was deemed "hazardous".

The balance of forces in Western Europe and Italy, Spring 1945[a]
Allied Soviet[9]
W. Europe Italy Total Operational forces Stavka reserve Total Ratio
Manpower 5,077,780[10][b] 1,333,856[11] 6,411,636 6,750,149 431,838 7,181,987 1 : 1.12
Tanks and assault guns[c] c. 19,100[12][d][e] 3,100[13] 22,200 12,333[f] 324[g] 12,657 1.75 : 1
Artillery c. 63,000[14] 10,200[13] c. 70,200 114,344[h] 6,838[i] 121,182 1 : 1.73
Combat aircraft -- -- 28,000[15][j][16] 18,823[k] 624[l] 19,447 1.44 : 1
Motor vehicles 970,000[15] unknown unknown 366,959[m] 20,362[n] 387,321 over 2.5 : 1
The Projected Balance in Western Europe, 1 July 1945[17]
Allied Soviet Ratio
Infantry divisions[o] 80 228 1 : 2.85
Armored divisions[p] 23 36 1 : 1.57
Tactical aircraft 6,048[q] 11,802 1 : 1.95
Strategic aircraft 2,750[r] 960 2.86 : 1


In response to an instruction by Churchill of 10 June 1945, a follow-up report was written on "what measures would be required to ensure the security of the British Isles in the event of war with Russia in the near future".[18] US forces were relocating to the Pacific for a planned invasion of Japan, and Churchill was concerned that the reduction in supporting forces would leave the Soviets in a strong position to take offensive action in Western Europe. The report concluded that if the United States focused solely on the Pacific Theatre, Britain's odds "would become fanciful".[19]

The Joint Planning Staff rejected Churchill's notion of retaining bridgeheads on the Continent as having no operational advantage. It was envisaged that Britain would use its air force and navy to resist, but a threat from mass rocket attack was anticipated, with no means of resistance except for strategic bombing.

Subsequent discussions[edit]

By 1946, tensions and conflicts were developing between Allied-occupied and Soviet-occupied areas of Europe. They were seen as being potential triggers for a wider conflict. One such area was the Julian March (an area of southeastern Europe now split among Croatia, Slovenia and Italy), and on 30 August 1946 informal discussions took place between the British and US chiefs of staff concerning how such a conflict could develop and the best strategy for conducting a European war.[20] Again, the issue of retaining a bridgehead on the continent was discussed, with Dwight D. Eisenhower preferring a withdrawal to the Low Countries, rather than Italy, because of their proximity to the United Kingdom.

Possible Soviet awareness[edit]

In June 1945 senior Soviet Army commander Marshal Georgi Zhukov suddenly ordered Soviet forces in Poland to regroup and prepare their positions for defence.[citation needed] According to Edinburgh University professor John Erickson, Operation Unthinkable helps to explain why he did it. If the plans of the operation had been transmitted to Moscow by the Cambridge Five, that would explain the sudden orders to regroup and prepare for defence, however, it is just as possible that it was Soviet mistrust of Western Allies. If the Soviets had indeed known that the Western Allies were planning a possible attack, the element of surprise would have been lost before operations against the Soviets even began, further reducing the chances of Operation Unthinkable's success.

See also[edit]


  1. ^ Excludes Soviet non-operational forces, Soviet equipment in storage/repair/replacement depots, and Allied forces in other theatres
  2. ^ 3,065,500 American, 1,295,200 British, 437,140 French, 217,420 Canadian, 62,520 other.
  3. ^ Excludes SPGs for the Allies
  4. ^ Zaloga's figures do not provide a total for Commonwealth TDs, however the ratio of tanks to tank destroyers in the US ETO was approximately 6.57 : 1. Under those conditions, Commonwealth forces would have possessed approximately 640 tank destroyers by the end of the war.
  5. ^ Including 4,720 Stuart, 1,163 Chaffee, 7,709 Sherman 75/76, 709 Sherman Firefly, 636 Sherman 105, 108 Pershing, 549 Cromwell, 30 Challenger, 237 Comet, and 742 Churchill. US ETO tank destroyers included 427 Hellcat, 427 Wolverine, and 1,039 Jackson.
  6. ^ Including 976 heavy tanks, 6,059 medium tanks, 564 light tanks, and 73 special tanks. Assault guns amounted to 504 heavy, 758 medium, and 3,399 light.
  7. ^ Including 139 medium and 35 light tanks. Assault guns amounted to 16 heavy, 84 medium, and 50 light.
  8. ^ Including 45,921 mortars, 2,726 rocket launchers, and 13,558 AA guns.
  9. ^ Including 3,043 mortars, 148 rocket launchers, and 768 AA guns.
  10. ^ Including 14,845 American; the USAAF in ETO alone possessed 5,559 heavy bombers and 6,003 fighters.
  11. ^ Including 8,078 fighters, 4,991 ground-attack, 4,878 bombers, 876 reconnaissance, and 3,798 others.
  12. ^ Including 183 fighters, 173 ground-attack, 204 bombers, 64 reconnaissance, and 377 others.
  13. ^ Including 268,428 trucks.
  14. ^ Including 14,423 trucks.
  15. ^ Division-Equivalents for the Soviets
  16. ^ Division-Equivalents for the Soviets
  17. ^ Including 3,480 US, 2,370 Commonwealth, and 198 Polish.
  18. ^ Including 1,008 US, 1,722 Commonwealth, and 20 Polish.



  1. ^ Daniel Todman, Britain's War: A New World, 1942-1947 (2020) p 744.
  2. ^ a b Operation Unthinkable..., p. "1". Archived from the original on 16 November 2010. Retrieved 25 September 2015.
  3. ^ British War Cabinet, Joint Planning Staff, "Operation Unthinkable."
  4. ^ Costigliola, p. 336
  5. ^ a b Gibbons, p. 158
  6. ^ Lownie 2016, p. 148.
  7. ^ a b Reynolds, p. 250
  8. ^ Operation Unthinkable p. 22 Retrieved 2 May 2017
  9. ^ Великая Отечественная война: Действующая армия, "1 January 1945"
  10. ^ Zaloga, "Downfall 1945: The Fall of Hitler's Third Reich" p. 28
  11. ^ Jackson, "The Mediterranean and Middle East, Volume VI: Part III - November 1944 to May 1945" p. 230
  12. ^ Zaloga, "Downfall 1945: The Fall of Hitler's Third Reich" p. 29
  13. ^ a b История второй мировой войны 1939–1945 гг. Volume 10, Table 6, p. 261
  14. ^ S.L.A. Marshall "ON HEAVY ARTILLERY: AMERICAN EXPERIENCE IN FOUR WARS". Journal of the US Army War College. Page 10. "ETO," US forces in Western Europe, fielded 42,000 pieces of artillery; American forces comprised approximately 2/3 of the Allied effort during the campaign.
  15. ^ a b MacDonald, "The Last Offensive" p. 478
  16. ^ Air Force Statistical Digest, 1978 p. 156
  17. ^ "Operation Unthinkable," pp. 22-23. Retrieved 5 May 2018
  18. ^ Operation Unthinkable..., p. "30 (Annex)". Archived from the original on 16 November 2010. Retrieved 16 November 2010.
  19. ^ Operation Unthinkable..., p. "24". Archived from the original on 16 November 2010. Retrieved 12 May 2015.
  20. ^ Operation Unthinkable..., p. "35". Archived from the original on 16 November 2010. Retrieved 16 November 2010.



External links[edit]