Origins of the relation of the Allies
The alliance which was built between the United States and the Soviet Union was made to combat Hitler’s Third Reich as Hitler and the Nazis threatened both the capitalist West and the communist East. When the allies accomplished their goal in 1945 when Germany surrendered unconditionally, the Allies lost the one element which kept their relationship together. From then on, the relations between the Allies (mainly the US) and the Soviet Union would be devoured by tension.

Occupation Zones in Germany after WWII
Disagreements arose at the last two wartime conferences upon how the European map was to look like. These disagreements arose due to the differing ideologies (communism and capitalism). As a result of these disagreements, Germany was to be divided into 4 sectors (France, Britain, US, USSR). West Germany would be democratic and East Germany would be Communist. Berlin was another issue; it was to be divided
Occupational Zones: British (Orange), Soviet Union (Red), American (Yellow Green), and French (Blue) zones
Occupational Zones: British (Orange), Soviet Union (Red), American (Yellow Green), and French (Blue) zones
the same way although it lay in East Germany. Stalin greatly disapproved of this as he feared the idea that the US may control Europe (feared an attack by the West). As a result of this fear, Stalin set out the Berlin Blockade in 1948 in an attempt to contain the democratic capitalist ideologies of the West. Other ways in which alliances between the Soviet Union and the allies disintegrated is due to arguments over reparations in Germany. Britain and the US wished to help Germany recover. As for the Soviet Union, it wanted Germany to pay for its losses; for that reason, Stalin started using East Germany and East Berlin to help reconstruct the Soviet Union. The “Iron Curtain” had settled in Germany and the presence of two opposing ideologies in this one nation brought about tensions between the US and the Soviet Union as disagreements are inevitable when two differing opinions clash.

The Three Governments, having considered the question in all its aspects, recognize that the transfer to Germany of German populations, or elements thereof, remaining in Poland, Czechoslovakia and Hungary, will have to be undertaken. They agree that any transfers that take place should be effected in an orderly and humane manner.

Not only did these zones of occupation bring tensions amongst the superpowers but they also affected the German people. With the settlement of zones of occupations, millions of Germans and Poles were expelled from their homeland due to territorial annexation in Eastern Europe.

Here is the Protocol of the Zones of Occupation:

Molotov-Ribbentrop Pact (Nazi-Soviet Pact)
This non-aggressio
Criticism of the Nazi-Soviet Pact
Criticism of the Nazi-Soviet Pact
n pact occurred due to fear by Stalin and the Soviet Union. Stalin feared an attack by Germany and one of the reasons why he entered the Nazi-Soviet Pact was to ensure he would not immediately be attacked by Germany. Also, prior to the agreement of the Molotov-Ribbentrop Pact, there were the Soviet and Franco-British talks on a mutual defense pact in Moscow. This failed and therefore led to a more abundant insecure feeling by Stalin. For both of these reasons, the Nazi-Soviet Pact to occupy Poland (Soviets to get east of Poland and Germany to get west of Poland) occurred. The Allies greatly opposed the Nazis therefore when the Soviet Union made an agreement with Germany, it was certain that alliances between the Soviet Union and the Allies would be shaky, tense, and unstable for the years to come. This pact did not work for the advantage of the relationship between the Soviet Union and the Allies.

The Atlantic Charter (August 14, 1941)

On this day, Churchill and Roosevelt, leaders of the two strongest western powers, met to define the objectives or policies for post-war Europe which included the discouragement of expansionism, territorial or not, the restoration of sovereignty for all states, economic collaboration, security within each state, freedom to sail freely and disarmament. They believed that these objectives will bring about peace and even though this meeting happened before the Soviet Union joined the Allies, this meeting clearly showed the tensions between the conflicting ideologies of the western and the eastern powers due to the absence of the eastern powers. For example, one of the objectives wanted by the two western powers was the right of self-determination for European countries. Clearly, this would conflict with Stalin's policies later.

The Atlantic Charter:

Follow the link for info on Stalin's domestic policies.