This book examines India's sub-imperial role in the acquisition and administration of British-controlled territories along the Indian Ocean littoral. Through a series of regional and thematic case studies, Thomas R. Metcalf demonstrates how exportable elements of the British Raj – its laws, architecture, military and labour – enabled ‘British imperial conquest, control, and governance across a wide territory stretching from Africa to eastern Asia’ (p. 1). His aim is twofold: to challenge the idea that Britain's empire was simply a series of vertical relationships between one metropole and several colonies by revealing a horizontal ‘web’ of imperial power linking colonies together; and to draw the attention of Indian Ocean historians to this period of British regional dominance. The apex of Indian sub-imperial expansion (1890–1920) coincided with the partition and settlement of East Africa, as well as the growth of Indian nationalism in both East and South Africa. While Metcalf only lightly accounts for subsequent nationalist politics generated by these South Asian communities, he does offer a useful guide to the expansion of British India's imperial machinery into Africa.

The opening chapter on colonial governance is the book's strongest. Metcalf traces the origin of the Indian codes within the Raj and their subsequent legal expansion into the Straits settlement, Malaya and East Africa. It was a gradual process – in Zanzibar, the Indian penal code was enacted in 1867, and further Indian Acts followed in 1884. Arthur Hardinge enacted the Indian codes for the mainland East African Protectorate in 1897 because he found them ‘simpler than English laws’ and therefore more suitable for administrators typically lacking in legal training (p. 24). By the 1920s, however, Kenya's white settlers sought to replace Indian codes with English law, a position which the Colonial Office – itself often in rivalry with the India Office – viewed with sympathy. These political dynamics, combined with ascendancy of indirect rule principles, moved colonial governors to enact new codes based on English law in every East African colony during the 1930s; by the 1950s, the legacy of Indian codes had mostly eroded. Britain also imported the Indian residency system to Zanzibar, and expanded it to Uganda through the work of the India-raised Frederick Lugard. Hardinge modelled the East African Protectorate's administrative structure closely along Indian lines, with district collectors and commissioners instead of generic ‘district officers’. In these ways, India provided ‘inspiration, precedents, and personnel’ (p. 45) for colonial administration. Subsequent chapters examine thematic cases, such as colonial ‘Saracenic’ architecture in Malaya, and Indian Army campaigns in the Indian Ocean littoral. Metcalf also considers the fantastic visions of Percy Cox, Mark Sykes and other advocates of Indian colonization in Mesopotamia and East Africa as rightful spoils following the First World War.

Readers seeking to learn about Indian Ocean cultures should look elsewhere; these are vignettes of colonial statecraft, produced mainly from official correspondence of the India Office, Colonial Office and Indian government. Although these sources richly illustrate imperial connections, they often do so through a narrow set of concerns which the author closely follows. The case of South Africa's importation of South Asian indentured labour between the 1830s and 1910s boasts a relatively robust historiography to which Metcalf contributes by examining the correspondence of labour recruiters in India. He shows that recruiters operated from caste and regional stereotypes and were prone to abuse by recruiting unhealthy workers, but that various Indian government safeguards, such as its ‘protector’ system, at least somewhat ameliorated the worst excesses of abusive recruitment tactics. The final chapter examines the well-known case of the construction of the Mombasa–Victoria railway, and offers some eye-opening details – such as the selection of rail gauge to match India rather than Sudan or South Africa – to demonstrate India's role at all levels of this project, not just in its provision of Punjabi ‘coolies’. Metcalf paints a fair picture of East Africa's economically diverse and politically engaged South Asian population, though he gets a few details wrong – A. M. Jeevanjee was a Bohora, not a Parsi (p. 199).

Metcalf's main point, that British India played a far greater role in Britain's Indian Ocean colonies than imperial or area historiographies suggest, is an undoubtedly correct one that deserves a wide hearing. More interesting but problematic is the book's concluding argument that periodizes the end of this sub-imperial role. Metcalf argues that a series of developments occurring roughly around 1920 – the end of indentured labour, new restrictions on Indian immigration within the British empire, the withdrawal of potentially mutinous Indian troops from Indian Ocean littoral stations, the take-off of a territorial anti-colonial Indian nationalism, the withdrawal of the rupee as East Africa's currency and the precipitous decline of ‘Saracenic’ architecture – all mark the retreat of British India from the Indian Ocean arena. This is part of a larger argument Metcalf makes about Indian history: that, during the 1930s to 1980s, India largely cut itself off from world markets and reduced its global presence, ultimately at its own great expense. While much is generally true in this periodization, 1920 did not mark an abrupt end to East Africa's specific connections with India. Indian skilled labour continued to immigrate to East Africa in significant numbers during the 1920s to 1950s, while mercantile links between the two regions similarly strengthened. Most strikingly, the idea of ‘Greater India’ continued to flourish throughout East Africa during the interwar years. During this period, East African Indians were not ‘rootless cosmopolitans’ cut off from their homeland (p. 214), but instead closely followed political developments in India, established vibrant regional and territorial political bodies, hosted a steady stream of speakers from the Indian National Congress, Arya Samaj and Muslim League, and lobbied the Indian government and India Office to advocate in disputes against colonial legislative restrictions. India's relative interest in the Indian Oean world may have declined after 1920, but this was not reciprocated by its former ‘sub-colonies’. That said, this is an invigorating and most useful book that deserves a wide readership among Africanists as well as Indian Ocean specialists.