The Renaissance jurist Alberico Gentili once quipped that, just like comedies, all wars end in a marriage. In medieval and early modern Europe, marriage treaties were a perennial feature of the diplomatic landscape. When one ruler decided to make peace with his enemy, the two parties often sealed their settlement with marriages between their respective families. In After Lavinia, John Watkins traces the history of the practice, focusing on the unusually close relationship between diplomacy and literary production in Western Europe from antiquity through the seventeenth century,...