It was merely a case of "my enemy is your enemy so we must be allies". The reason why Britain allied with the Russians was it was a major power and needed their help to make sure that Germany would lose the war, however they never truly trusted them. Also, the US become allies with the USSR as it was allies with Britain. In addition to this the US knew that if the USSR allied with Germany, they wouldn't stand a chance and the outcome of the war would be different.
The US, Soviet Union, and Great Britain
Great Britain
Great Britain, Soviet Union, USA and France.
Great Britain, Soviet Union, USA and France.
the u.s. great Britain soviet union France
US, Great Britain, Soviet Union.
That would be the country of Greece, which had long been considered a protectorate of Great Britain.
U.S., Great Britain, France and Soviet Union
U.S., Great Britain, and the Soviet Union.
France, Great Britain, and the Soviet Union
The united states, great britan, and the Soviet Union
U.S. Great Britain, and the Soviet Union