Like other European colonial powers in Africa, Germany used the abolition of the slave trade and slavery to justify its imperialist expansion in East Africa in the late 1880s. However, unlike other European powers in Africa, Germany never formally abolished slavery in German East Africa, adopting instead a series of measures that curtailed the generation of new slaves while the colonial state regulated slavery as a legal institution until the end of German rule. Despite the colonial state's self-interest in maintaining slavery, or – perhaps better put – resisting abolition, many slaves succeeded in obtaining freedom. Jan-Georg Deutsch seeks to explain how they were able to do this in this study, which fills an important gap in our understanding of German colonialism in East Africa.

The book is divided into three sections, examining the conditions of slavery in the territory that would become German East Africa, German abolitionist policy, and the ways in which slaves obtained freedom. The first section focuses on the northern coast and Unyamwezi in Central Tanzania. Following the work of Abdul Sheriff, Deutsch underscores the role of the emergent nineteenth-century global economy in incorporating East Africa through the Zanzibar commercial entrepôt. On the coast this meant that slavery was generated by a plantation-owning Muslim elite that needed a labor force to produce grain and other cash crops for export to Zanzibar. As a result, on the eve of colonial conquest, perhaps half the populations of some coastal districts were slaves, working as peasants, artisans, domestic servants, concubines, stevedores, sailors and soldiers. Deutsch largely adopts Jonathon Glassman's view that slaves sought social advancement through greater incorporation into coastal urban institutions and the kinship groups of their masters. In Unyamwezi, slavery was generated by the need to provision the ivory and slave caravan trade that passed through Tabora and the subsequent need to maintain the domestic economy in the absence of thousands of young men, who left to work as caravan porters for long durations. While the majority of slaves in agricultural production were women, Deutsch points out that many inland chiefs employed male slaves as ruga-ruga soldiers in an era of pronounced violence. In Unyamwezi, kinship, rather than Islamic norms, determined the relative servility or social inclusion of slaves. Deutsch argues that most of the mechanisms for the eventual waning of slavery during the colonial period were in operation before colonial conquest. Among these were voluntary manumission by owners; negotiated semi-freedom that enabled some slaves, especially men, to work in the commercial economy in exchange for a portion of their earnings; social mobility, which enabled some slaves to rise to positions of trust within their owners' own extended families; and flight.

The second section details the layers of colonial thinking on slavery and abolition in German East Africa, ultimately concluding that actual practice stemmed from the governors of German East Africa and district officials. Between 1891 and 1905 four laws in particular established the parameters of abolition in German East Africa, which cut off the supply of most new slaves by curtailing violent enslavement from 1890 and made children of slaves born after 1905 legally free. Other laws from 1891 allowed slaves to purchase their freedom or allowed third parties – family members, plantation owners, missionary societies – to ransom slaves into freedom by paying an agreed-upon price to their masters. Despite these measures, new slaves continued to be generated during German rule by pawnage at times of famine and by violent capture during warfare under the aegis of colonial pacification. Non-violent slave trading was allowed, even taxed and regulated, at the district level, although its extent varied from district to district. Although a third of all freedmen and women received freedom through voluntary manumission, it was up to most slaves to wrest their own freedom through flight or by taking advantage of opportunities to work in the colonial economy as wage laborers in towns, as porters, railway workers, and plantation workers on German estates, with men being at a distinct advantage.

Why did Germany refuse to end slavery outright? Deutsch is reluctant to embrace a conclusive answer, although he suggests that German officials feared the ‘threat of social upheaval by unfettered capitalism’ (p. 129 fn. 102) and disorder from an ‘unattached African working class’ (p. 112) made up partly of former slaves. Yet German policies clearly aimed to create an African wage-earning class, the ‘labor question’ being the most consistent thread in German colonial policy in East Africa. It seems unlikely, therefore, that German officials were reluctant to channel slaves into the wage labor force when their ransoming policy did just that. Deutsch is on firmer ground when he cites colonial dependence on a slave-owning class of African functionaries and plantation owners as a key reason for German East Africa's incomplete path to abolition.

This is an impressive study given the fragmentary nature of available sources. Deutsch has mastered the sources from the German Federal Archives, and published and secondary literature on the topic. Surprisingly, he neglects the Swahili sources from the Preussischer Geheimes Staatsarchiv, which contain important evidence on slavery on the northern coast in the 1890s. Nor does Deutsch use relevant criminal files from the Tanzania National Archives – which provide evidence of slave criminality, thus slave resistance – to an appreciable degree. Deutsch furthermore omits plantation records, particularly those from Mafia Island, which are the richest sources on slave ransoming. Despite these gaps, this work will set the standard for our understanding of slavery and abolition in German East Africa for the foreseeable future.