This book skillfully reconstructs the political maneuverings of the heads of the Colonna family, one of Rome's wealthiest and most prestigious baronial families, across the period from 1430 to 1530. By 1550, in the “glorious defeat” of the title, the Colonnas found themselves reduced from “true lords of their own lands” in the papal states (11) to vassals dominated by the papacy and the Spanish crown. Within this familiar story of the decline of the feudal and baronial aristocracy, Serio offers some nuances to prevailing wisdom. He places the shift to papal dominance in the mid-sixteenth century, rather later than others, and delineates a long period of transition and upheaval over the course of the Wars of Italy, 1494–1530. During this transition, he argues, the heads of the Colonna clan by and large cooperated in their own defeat, salvaging what power they could in a rapidly changing political environment.

Serio's analysis of the family's internal negotiations and conflicts is particularly valuable, the fruit of research in vast and varied documentation drawn from Vatican, Spanish, and family archives. After the death of Pope Martin V (Colonna) in 1431, a brief initial power struggle among his heirs was resolved quickly, though not without bloodshed. Thereafter, Serio shows, the principal Colonna branch of Palestrina and the secondary branch of Genazzano negotiated to keep properties undivided and authority lines clear, by consolidating landholdings, sharing residences, and retaining male primogeniture in the main patriline of each branch, though not in the other lines secondary. Serio perceptively reconstructs the complicated, often unspoken hierarchies and authority structures within the family, calling attention to cooperation between ecclesiastical and lay family heads, the roles of clerical brothers and mothers, and the increasingly wide gulf in horizons between the greater and lesser members of the family. The system worked until 1528, when the Genazzano leader Vespasiano died and left his estate to his daughter Isabella rather than his second cousin Ascanio Colonna, causing a long-term rift.

The lineage solidified its alliance with Aragon, then Spain only during the pontificate of Julius II (1503–13), in response to Julius's effective limiting of baronial power. Marriage alliances with high-ranking Neapolitan families in 1509 and 1513 further strengthened the bond. After 1513, Colonna efforts to expand their influence in Lombardy and the Po Valley clashed with Medici ambitions, ultimately throwing the Colonnas back on their power base in the south and further into the arms of Charles V. The dynasty emerged from the Wars of Italy as solid members of the Neapolitan elite: in 1516 Charles confirmed Fabrizio Colonna as Gran Connestabile del Regno and made the office hereditary.

In the urbs, the Colonnas, like the other baronial families, came somewhat late to the Renaissance party of grand classicizing palaces, literary commissions, and archaeology, trends pioneered by the new curial aristocracy in the second half of the fifteenth century. Despite regular episodes of residence in Rome and the maintenance of a neighborhood clientele around the family palace of Santissimi Apostoli, the family's primary power base continued to lie in the provinces; its wealth, in the pastoral and agricultural activities of those lands; its central administration and archives, in country seats like Genazzano and Marino; its forms of cultural expression, in the military. Only after 1500 did the Colonna slowly make the transition to a more urban and courtly lifestyle. A brief epilogue and conclusion identify Ascanio Colonna's quixotic Salt War against the papacy in 1541 as the last blast of the Colonna family's independent military trumpet.

The book's laser-beam focus on a single family whets the appetite for more context of various kinds. Did the Colonna experience and strategies parallel those of others in their class, or were they an unusual case? What groups benefited from their marginalization? This is histoire evenementielle: aside from a few references to the extensive literature on early modern Roman elites, Serio softpedals the longer-term changes to economic and political structures that underlay the Colonnas’ decline. Nonetheless this impressive archival study offers a rich basis on which to continue the conversation.