Manning takes Robin Law's study of Oyo as about as full an interpretation as the evidence then allowed, combining political narrative with cross-sectional analysis of the capital, the army and the provinces.

Cavalry does much of the explanatory work. Horses account for Oyo's power and for the empire's shape, since its reach stopped where the ground no longer suited mounted warfare, and the Alafin's dependence on cavalry he did not personally control sharpened the constitutional crisis. Manning follows the sequence from Gaha's seizure of power in 1754 to Abiodun's counterstroke in 1774, which installed provincial chiefs as a third force at the capital and left the underlying conflict unsettled until provincial revolts brought the state down.

He is warier than Law about the slave trade, suspecting smaller export volumes and reading the surge of the 1780s as an answer to rising prices. The book, he concludes, is careful synthesis rather than new argument.

The kingdom of Allada dominated slave exports from the western Bight of Benin before Dahomey's conquests of the 1720s, yet its earliest phase has been treated thinly or misleadingly in the standard accounts. Law reworks the numbers, discarding decade-by-decade tabulation in favour of a periodisation drawn from the trade's own political history.

Two corrections follow. Portuguese activity in the sixteenth and early seventeenth centuries, judged negligible by earlier scholars, looks larger once the fiscal basis of the surviving valuations is read correctly; the mid-century Dutch and English trade, by contrast, looks smaller. Sustained growth begins only in the later 1670s.

Law also stresses how violently the traffic fluctuated year to year, disrupted by the Anglo-Dutch wars. That matters for interpretation: falling slave prices between the 1650s and 1670s accompanied stagnation rather than the expanding African supply earlier explanations assumed.