The British and the Spanish had long been in conflict, often clashing over politics, trade, and religion. But in the early decades of the eighteenth century, these empires signed an asiento agreement granting the British South Sea Company a monopoly on the slave trade in the Spanish Atlantic, opening up a world of uneasy collaboration. British agents of the Company moved to cities in the Caribbean and West Indies, where they braved the unforgiving tropical climate and hostile religious environment in order to trade slaves, manufactured goods, and contraband with Spanish colonists....