With the development of the "Industrial Revolution" the need for labor force is replaced by that of raw materials, thus giving boost to imperialism. In the second half of the XIX century the great colonial powers share out the rest of the world, starting the formation of vast colonial empires that cover more than half of the lands above sea-level.
Only after the "Second World War" decolonization spreads rapidly, though leaving countries that, even if formally independent, continue to be dependent on the old "metropolis".
For further information:
Animated Atlas of African History 1879 - 2002
Britain should stop trying to pretend that its empire was benevolent
Viewpoint: How British let one million Indians die in famine
Britain’s colonial crimes deserve a lasting memorial. Here’s why
Auschwitz to Rwanda: the link between science, colonialism and genocide
Colonial Frontier Massacres in Eastern Australia 1788-1872
Germany: Confronting the colonial roots of racism
The First NATO: British and French Joint Aggressions in the Mid-19th Century
Addressing our histories of colonialism and historic slavery
Colonial crimes | DW Documentary
The British Empire Was Much Worse Than You Realize
How Britain stole $45 trillion from India
How British colonialism killed 100 million Indians in 40 years
How colonial Germany extended its empire in Africa
No justice: 75 years after a British massacre in colonial Malaya
