Prelude to the Collapse of the Colonial Empires

The wolves of European colonialism mainly managed to avoid general war among themselves while extending their empires over the rest of the world. By 1900, they were running out of other peoples' land to steal or otherwise colonize. So they turned, once again, on each other.

The most vital prop of Europe’s primacy in Eurasia, and of the powerful position of the great European states in the Outer World beyond, had been their collective determination not to fight each other. It had been this and the Atlantic peace between Europe and the Americas that had allowed the rapid growth of international trade, the steady extension of European influence and authority, and the ironic achievement of the African partition. The reluctance of European governments to upset their continental balance of power and risk the social and political upheaval that a general war would bring had restrained their pursuit of national and imperial advantage.

Darwin, John (2010-08-08). After Tamerlane (p. 370). Bloomsbury Publishing Plc. Kindle Edition.

1914 ended that. Of course there were other, internal strains, economic, ethnic, religious and ideological that were ripping the old order apart. Meanwhile, colonial resistance was crystallizing, and the calamities of the mid-twentieth century weakened the power, prestige, and moral self-confidence of the colonizers, as well as exposing their dependence on the colonies.