What is the meaning of 'Period of Decolonization'? Explain?

1)       Decolonization started after the Second World War.
2)       It came to an end at the turn of the twentieth (20th) century.
3)       Asian and African countries which were ruled by England, France, Holland and Portugal became free in the twentieth century.

4)       The period covering the later half of the 20th century is known as the 'Period of Decolonization' as colonialism came to an end during this period.