• This report was submitted to British Prime Minister Winston Churchill in May 1945. It was known as Operation Unthinkable.
  
• Churchill asked the Joint Planning Staff (the top British military commanders) to see whether they thought war with Russia was a realistic option.
  
• In May 1945 Churchill was extremely concerned about the actions of Soviet leader Stalin, particularly in Eastern Europe.
  
• At the Yalta Conference in February 1945 Stalin agreed that Eastern European states would be able to choose their own governments. By May 1945 Churchill felt Stalin was not going to stick to his promise.
  
• Churchill rejected the plan very quickly. His military advisers were convinced that it would be very difficult to defeat the USSR in a war.