Volume IV of the Oxford History of the British Empire not only relates the history of the Empire in the twentieth century in a British context but also assesses the significance of colonial rule for peoples under British sway. The rise of nationalism and the coming of colonial independence are two of the volume's principal concerns.
The themes of the Empire's economy, the White Dominions in relation to migration and security, India's special position in the Empire, and the administration of the colonies, all build on the foundation of Volume III, The Nineteenth Century. As in the previous volumes, some chapters in The Twentieth Century choose an earlier point of departure than might be suggested by the sharp hundred-year breaks. The twentieth-century Empire cannot be understood without taking into account the expansion of the Empire into Africa and the Pacific in the latter part of the nineteenth century and the consolidation of colonial rule in the decades before the First World War. Some chapters commence by examining the Victorian legacy. Others respect the view that the reach of the nineteenth century extended to 1914. There is a similar ambiguity on the point of termination. The Empire came to an end mainly in the 1960s in the era of African independence. Yet certain important but quite different issues remained unresolved until the closing decades of the century: the conclusion of the Rhodesian crisis with Zimbabwean independence in 1980, the end of the apartheid regime in South Africa in 1991, and the return of Hong Kong to China in 1997. The volume thus explicitly embraces different views on the periodization of the Empire's history in the twentieth century.
At the turn of the century few anticipated the rapid changes in the Empire and fewer still its dissolution. By 1910 Canada, Australia, New Zealand, and South Africa had all become self-governing Dominions, but the issue of self-rule in Ireland, and later in India, divided the British public. Ireland was a member of the Commonwealth from 1922 until 1949; but as late as 1947 it was still uncertain whether an independent India would remain associated with Britain by joining the Commonwealth. India's decision not to break away is fundamental to the volume as a whole. India set the precedent for other non-European nations to join the Commonwealth, thus enabling over fifty states to be Commonwealth members at the end of the twentieth century. This long-range development has affected the way the history of the Empire and Commonwealth has been often written. India's decision strengthened the Whiggish view of the Empire's progress and purpose