The Grand Alliance, or Big Three as they’re also known, was a military alliance consisting of Joseph Stalin for the Soviet Union, Franklin D. Roosevelt for the US, and Winston Churchill for the UK. We have their (mostly) cordial working relationship to thank for the victory against Nazi Germany and the way the post-war world was shaped.

Stalin, Roosevelt and Churchill managed to achieve all this and more by meeting up for three wartime conferences; Tehran in 1943, and Yalta and Potsdam in 1945. Just so you know, Roosevelt got sick and died during the course of the Potsdam Conference and he was replaced by Vice-President Harry Truman.

But before this happened, Churchill and Roosevelt also met at the Atlantic and Washington Conferences in 1941, the Second Washington Conference in 1942, at Casablanca, Washington, Quebec, and at the First and Second Cairo Conferences during 1943, at the Second Quebec Conference in 1944 and at the Malta Conference in 1945. So, a lot.

Despite the Grand Alliance’s good wartime working relationship, the Big Three still had their differences – particularly those of the political and economic variety. For instance, both the US and UK saw Russia as a threat to their capitalist-based free-market economies. Because of this, they were suspicious of Stalin’s motives out of fears he would try and spread Communism to Western Europe and beyond post-war.

These concerns became more apparent as the end of the war approached. By 1945 the Red Army had freed Eastern Europe from Nazi occupation and Roosevelt and Churchill were concerned that Stalin might force Communism on these countries and that it would be difficult to prevent him from occupying Western Europe as well. They were also concerned that the population of Europe, who faced a wrecked infrastructure, starvation and refugees, might turn to Communism as the political and economic solution to their problems.

These concerns were pretty much down to Churchill, who had a long-standing and outspoken mistrust of Communism that pre-dated WWII. In fact, Churchill hated the idea of Communism and the Soviet Union so much that he coined the term “Iron Curtain” to describe the division of post-war Europe. The term was first used in a telegram that Churchill sent to Harry Truman before being used in public during an iconic speaking tour of Fulton, Missouri, on 5 March 1946.

That being said, Churchill’s fears weren’t baseless; the sheer size of the Red Army would have made it difficult to contain, had Stalin decided to push on into Western Europe in the years following the end of WWII.

Meanwhile, Stalin was concerned that the invasion of Western Europe by the UK and US was being deliberately delayed in the hope that Communism and Nazism would destroy each other before the British and Americans launched D-Day. So basically, it was a bit of a “trust no one” situation.