The Soviet Union was an ally of the UK during World War 2 in order to defeat Nazi Germany. However, their alliance was a tense, strained one that was often pushed to its limits. For example, in November 1941, Stalin had the gall to criticise the quality of British tanks and guns sent to help Soviet forces. Related articles NASA Moon landing BOMBSHELL: How Winston Churchill made SHOCK call EU WARNING: What made Churchill think bloc would be a ‘DISASTER' However, it has now emerged that the General Secretary of the Communist Party realised his mistake and sought to change the mood of their relationship. On Churchill’s 67th birthday, Stalin sent a very out-of-character gushing birthday ‘card’ to him to make amends. The coded telegram said: “To the Prime Minister Winston Churchill, I warmly congratulate you on your birthday. “From the bottom of my heart I wish you strength and health, which are so necessary for the victory over the enemy of mankind, Hitlerism. Joseph Stalin and Winston Churchill (Image: GETTY) Joseph Stalin and Winston Churchill (Image: GETTY) “Accept my best wishes, Stalin.” The revelation was made by historian David Reynolds at the Chalke Valley History Festival. Professor Reynolds is a fellow of Christ’s College, Cambridge and co-author of The Kremlin Letters. He claimed the message was likely prompted by Stalin’s ambassador the the UK, Ivan Maisky. Related articles ‘Adolf Hitler is ALIVE’ Joseph Stalin’s warning to Harry Truman THR... WW3: Why US feared Soviet nuclear missile attack from SPACE He added that Stalin would not openly admit he was wrong, but was “clearly shifting the mood”. He said: “Stalin is not known for sending birthday wishes. “Certainly not to a capitalist imperialist who was renowned for threatening to strangle Bolshevism in its cradle. “My supposition is that Maisky the ambassador told Stalin it was Churchill’s birthday and maybe encouraged this kind of message. “Maisky was very savvy about this sort of thing. Joseph Stalin, Franklin D Roosevelt and Winston Churchill (Image: GETTY) Stalin and Churchill at Yalta Conference (Image: GETTY) “At any rate, it’s an extremely clever plot – Stalin is certainly not going to admit he went over the top early on, but it’s clearly shifting the mood in a way that’s very important in the closing." Mr Churchill apparently replied to the message thanking Stalin and claiming his note gave him “lively pleasure”. The wartime Prime Minister also returned the favour on Stalin’s birthday the following month and the exchanges then became something they continued even after the end of the war. It ground to a halt however, after Mr Churchill’s inflammatory ‘Iron Curtain’ speech. Professor Reynolds said: “I think the last birthday message in the 1940s is sent by Churchill in the autumn of 1946 after his ‘Iron Curtain’ speech.”All rights reserved for this news site express.co.uk and under his responsibility