The end of European power
The influence of the great European states like Britain and France had already started to weaken before 1939. The Second World War sped up this process of decline and the world after 1945 was to be dominated by just two super powers, the United States and Russia. However, neither Britain nor France realised this straight away. They continued to behave for another ten years or so as though they could still influence world events.
The war and the early defeats suffered by the British at the hands of the Japanese showed the peoples ruled by the British and French empires that the Europeans could be beaten. These peoples were not willing to welcome back their old colonial rulers. The Vietnamese fought the French and Britain faced rebellions in her African colonies. The Labour government quickly agreed to the independence of India in 1947.
Neil Demarco: The era of the Second World War; Oxford University Press, 1993/2000, page 74